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Journal articles on the topic 'Boreholes'
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1
Eyre, Natalie S., Antony J. Payne, Duncan J. Baldwin, and Helgi Björnsson. "The use of salt injection and conductivity monitoring to infer near-margin hydrological conditions on Vestari-Hagafellsjökull, Iceland." Annals of Glaciology 40 (2005): 83–88. http://dx.doi.org/10.3189/172756405781813410.
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AbstractVestari-Hagafellsjökull is a surge-type outlet glacier from the Langjökull ice cap, Iceland. Intensive hydrological investigations were carried out during non-surge conditions in the summers of 1999 and 2000, and 14 boreholes were drilled using pressurized hot water over an area 800 m from the margin and approximately 5000 m2 in size, where ice thickness ranged from 60 to 70 m. Initial investigations showed that a large fraction of the boreholes drilled to the bed did not drain and were assumed not to connect to the subglacial drainage system. Subsequently, we investigated the hypothesis that boreholes which remain full may do so as a consequence of a balance between englacial inflow and basal drainage rather than the standard assumption that such boreholes are simply unconnected. In testing this hypothesis, we developed a new technique for measuring water motion within the borehole by monitoring the passage of a saline solution down the borehole’s water column. The technique allows rates of motion to be established, as well as allowing the quantification of net addition and loss of water from the borehole. Observations based on the motion of saline plumes within the boreholes lead us to the conclusion that some boreholes do indeed remain full as a consequence of a balance between englacial inflow and subglacial drainage. The abrupt dilution that occurs at the top of these boreholes suggests inflow from a near-surface englacial water source, while the descent of the saline plumes implies that water is being lost at the base to the subglacial system. The system appears to be driven by excess water head in the boreholes over flotation and implies that the borehole/bedrock interface can be ‘leaky’.
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Chen, Yuxin, Yunhong Ding, Chong Liang, Dawei Zhu, Yu Bai, and Chunmei Zou. "An Analytical Model for Fracture Initiation from a Particular Radial Borehole in Hydraulic Fracturing Guided by Multiradial Boreholes." Geofluids 2021 (February 11, 2021): 1–18. http://dx.doi.org/10.1155/2021/6657788.
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Radial drilling-fracturing, the combination of the hydraulic fracturing and radial borehole, is a technology that can guide the hydraulic fractures to directionally propagate and efficiently develop low permeability reservoir. In this paper, an analytical model of two radial boreholes (a basic research unit) is established to predict fracture initiation pressure (FIP) from one particular radial borehole and the interference between radial boreholes when the hydraulic fracturing is guided by multi-radial boreholes. The model is based on the stress superposition principle and the maximum tensile stress criterion. The effects of in situ stress, wellbore pressure, and fracturing fluid percolation are considered. Then, sensitivity analysis is performed by examining the impact of the intersection angle between radial boreholes, the depth difference between radial boreholes, the radius of radial boreholes, Biot coefficient, and the number of radial boreholes. The results show that FIP declines with the increase of radial boreholes number and the decrease of intersection angle and depth difference between radial boreholes. Meanwhile, the increase of radial borehole number and the reduction of intersection angle and depth difference strengthen the interference between radial boreholes, which conduce to the formation of the fracture network connecting radial boreholes. Besides, FIP declines with the increase of radial borehole radius and the decrease of Biot coefficient. Large radius and low Biot coefficient can enlarge the influence range of additional stress field produced by radial boreholes, enhance the mutual interference between radial boreholes, and guide fracture growth between radial boreholes. In hydraulic fracturing design, in order to reduce FIP and strengthen the interference between radial boreholes, the optimization design can be carried out by lowering intersection angle, increasing radius and number of boreholes, and reducing the depth difference between boreholes when the conditions permit. The research clarifies the interference between radial boreholes and provides the theoretical basis for optimizing radial boreholes layout in hydraulic fracturing guided by multi-radial boreholes.
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Sliwa, Tomasz, Aneta Sapińska-Śliwa, Andrzej Gonet, Tomasz Kowalski, and Anna Sojczyńska. "Geothermal Boreholes in Poland—Overview of the Current State of Knowledge." Energies 14, no. 11 (June 2, 2021): 3251. http://dx.doi.org/10.3390/en14113251.
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Geothermal energy can be useful after extraction from geothermal wells, borehole heat exchangers and/or natural sources. Types of geothermal boreholes are geothermal wells (for geothermal water production and injection) and borehole heat exchangers (for heat exchange with the ground without mass transfer). The purpose of geothermal production wells is to harvest the geothermal water present in the aquifer. They often involve a pumping chamber. Geothermal injection wells are used for injecting back the produced geothermal water into the aquifer, having harvested the energy contained within. The paper presents the parameters of geothermal boreholes in Poland (geothermal wells and borehole heat exchangers). The definitions of geothermal boreholes, geothermal wells and borehole heat exchangers were ordered. The dates of construction, depth, purposes, spatial orientation, materials used in the construction of geothermal boreholes for casing pipes, method of water production and type of closure for the boreholes are presented. Additionally, production boreholes are presented along with their efficiency and the temperature of produced water measured at the head. Borehole heat exchangers of different designs are presented in the paper. Only 19 boreholes were created at the Laboratory of Geoenergetics at the Faculty of Drilling, Oil and Gas, AGH University of Science and Technology in Krakow; however, it is a globally unique collection of borehole heat exchangers, each of which has a different design for identical geological conditions: heat exchanger pipe configuration, seal/filling and shank spacing are variable. Using these boreholes, the operating parameters for different designs are tested. The laboratory system is also used to provide heat and cold for two university buildings. Two coefficients, which separately characterize geothermal boreholes (wells and borehole heat exchangers) are described in the paper.
4
Fudge, T. J., Neil F. Humphrey, Joel T. Harper, and W. Tad Pfeffer. "Diurnal fluctuations in borehole water levels: configuration of the drainage system beneath Bench Glacier, Alaska, USA." Journal of Glaciology 54, no. 185 (2008): 297–306. http://dx.doi.org/10.3189/002214308784886072.
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AbstractWater levels were measured in boreholes spaced along the entire length of Bench Glacier, Alaska, USA, for a period in excess of 2 years. Instrumented boreholes were arranged as nine pairs along the center line of the glacier and an orthogonal grid of 16 boreholes in a 3600 m2 region at the center of the ablation area. Diurnal fluctuations of the water levels were found to be restricted to the late melt season. Pairs of boreholes spaced along the length of the ablation area often exhibited similar fluctuations and diurnal changes in water levels. Three distinct and independent types of diurnal fluctuations in water level were observed in clusters of boreholes within the grid of boreholes. Head gradients suggest water did not flow between clusters, and a single tunnel connecting the boreholes could not explain the observed pattern of diurnal water-level fluctuations. Inter-borehole and borehole-cluster connectivity suggests the cross-glacier width of influence of a segment of the drainage system connected to a borehole was limited to tens of meters. A drainage configuration whereby boreholes are connected to a somewhat distant tunnel by drainage pipes of differing lengths, often hundreds of meters, is shown with a numerical test to be a plausible explanation for the observed borehole behavior.
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Morin, Roger H., Guillaume E. Descamps, and L. DeWayne Cecil. "Acoustic televiewer logging in glacier boreholes." Journal of Glaciology 46, no. 155 (2000): 695–99. http://dx.doi.org/10.3189/172756500781832684.
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AbstractThe acoustic televiewer is a geophysical logging instrument that is deployed in a water-filled borehole and operated while trolling. It generates a digital, magnetically oriented image of the borehole wall that is developed from the amplitudes and transit times of acoustic waves emitted from the tool and reflected at the water–wall interface. The transit-time data are also converted to radial distances, from which cross-sectional views of the borehole shape can be constructed. Because the televiewer is equipped with both a three-component magnetometer and a two-component inclinometer, the borehole’s trajectory in space is continuously recorded as well. This instrument is routinely used in mining and hydrogeologic applications, but in this investigation it was deployed in two boreholes drilled into Upper Fremont Glacier, Wyoming, U.S.A. The acoustic images recorded in this glacial setting are not as clear as those typically obtained in rocks, due to a lower reflection coefficient for water and ice than for water and rock. Results indicate that the depth and orientation of features intersecting the boreholes can be determined, but that interpreting their physical nature is problematic and requires corroborating information from inspection of cores. Nevertheless, these data can provide some insight into englacial structural characteristics. Additional information derived from the cross-sectional geometry of the borehole, as well as from its trajectory, may also be useful in studies concerned with stress patterns and deformation processes.
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Doetsch, Joseph A., Ilaria Coscia, Stewart Greenhalgh, Niklas Linde, Alan Green, and Thomas Günther. "The borehole-fluid effect in electrical resistivity imaging." GEOPHYSICS 75, no. 4 (July 2010): F107—F114. http://dx.doi.org/10.1190/1.3467824.
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Fluid that fills boreholes in crosswell electrical resistivity investigations provides the necessary electrical contact between the electrodes and the rock formation but it is also the source of image artifacts in standard inversions that do not account for the effects of the boreholes. The image distortions can be severe for large resistivity contrasts between the rock formation and borehole fluid and for large borehole diameters. We have carried out 3D finite-element modeling using an unstructured-grid approach to quantify the magnitude of borehole effects for different resistivity contrasts, borehole diameters, and electrode configurations. Relatively common resistivity contrasts of 100:1 and borehole diameters of 10 and [Formula: see text] yielded, for a bipole length of [Formula: see text], apparent resistivity underestimates of approximately 12% and 32% when using AB-MN configurations and apparent resistivity overestimates of approximately 24% and 95% when usingAM-BN configurations. Effects are generally more severe at shorter bipole spacings. We report the results obtained by either including or ignoring the boreholes in inversions of 3D field data from a test site in Switzerland, where approximately 10,000 crosswell resistivity-tomography measurements were made across six acquisition planes among four boreholes. Inversions of raw data that ignored the boreholes filled with low-resistivity fluid paradoxically produced high-resistivity artifacts around the boreholes. Including correction factors based on the modeling results for a 1D model with and without the boreholes did not markedly improve the images. The only satisfactory approach was to use a 3D inversion code that explicitly incorporated the boreholes in the actual inversion. This new approach yielded an electrical resistivity image that was devoid of artifacts around the boreholes and that correlated well with coincident crosswell radar images.
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Zhang, Heng, Tie Li, Zhenhua Ouyang, Su Liu, and Haiyang Yi. "Research on Optimization of Coal Pressure Relief Borehole Parameters under High-Stress Conditions." Geofluids 2021 (August 31, 2021): 1–13. http://dx.doi.org/10.1155/2021/4673152.
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Determining the parameters of boreholes drilled for relieving pressure in coal seams is the key preventing and controlling rock bursts in boreholes of large diameter. In this study, theoretical analysis, numerical simulation, literature research, and other analysis methods are applied to study the angles of elastic energy dissipation and stress transfer, the distribution law of the pressure relief area, and the areas of stress concentration, energy, stress, displacement, and plastic behavior of large-diameter pressure relief boreholes in coal seams under high-stress conditions. The results are then used to evaluate the relationship between large-diameter pressure relief boreholes and the borehole arrangement. The following results are obtained. (1) A large-diameter results in a large amount of elastic energy released by the surrounding coal, low residual elastic energy density, strong interaction between boreholes, large pressure relief range of the borehole, and high pressure relief efficiency. (2) The main evaluation factor of the borehole pressure relief effect is its thickness and stress concentration area; secondary evaluation is based on the areas of energy, displacement, stress, and plastic behavior. (3) Six evaluation index systems are established to evaluate the effects of borehole pressure relief, which are found to be the thicknesses of the borehole pressure relief area and stress concentration area, reduction degree of energy density, percentage of stress reduction, displacement, and penetration degree of the plastic area. (4) It is determined that when the diameters of the pressure relief boreholes are 100, 120, 180, and 200 mm, a single-row borehole arrangement is adopted; a three-pattern borehole arrangement is adopted with diameters of 140 and 160 mm. These research results can provide theoretical support in selecting reasonable borehole arrangements for pressure relief boreholes of different diameters.
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Ademola, Iroye Kayode. "Effect of Down-Hole Lithological Variation on Water Bearing Capacity of Some Boreholes in Ilorin, Nigeria." Studia Universitatis Babeș-Bolyai Geographia 66, no. 2 (December 30, 2021): 5–23. http://dx.doi.org/10.24193/subbgeogr.2021.2.01.
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"Effect of Down-Hole Lithological Variation on Water Bearing Capacity of Some Boreholes in Ilorin, Nigeria. The paper attempts to explain the effect of downhole lithological variation on water bearing capacity of some boreholes in Ilorin Nigeria. Specifically, the study examined the lithological characteristics of the boreholes, assessed the variability in weathered overburden and analyzed the inter-relationships between lithology, hydrology and topography of the boreholes. Data used were extracted from twenty (20) borehole logs collected from the archive of Lower Niger Basin Development Authority in Ilorin. Information extracted from the borehole logs are: the number of lithological units intersected by each of the borehole and their depths, the nature of geological materials making up the lithological units and their moisture conditions. Information on coordinates and topographic heights of the boreholes are not given on the logs and those were collected from the field personally by the researcher using handheld GPS (Garmin GPS Channel 76 Model). The collected data were analyzed using descriptive statistics. Results reveal nine downhole lithological units with loamy and lateritic soil making up the first layer of lithology in 95% of the boreholes. Thickness of the top soil and the saprolite overlying the bedrock, has mean values of 4.2m and 11.3m respectively. Depth to water in the borehole ranged between 24.7 and 140m and with a mean value of 55.9m. Three (3) of the boreholes have two lenses of aquifer while the remaining seventeen (17) have one aquifer lens each. The three (3) boreholes with two aquifer lenses have their minor aquifers located within the saprolite. The main aquifer in most (65%) of the boreholes is located within the fractured basement while the remaining (35%) boreholes have their main aquifer located in the weathered basement. Correlation analysis revealed topographic elevation as one of the drivers of hydrology in the study area. Keywords: lithology, groundwater, saprolite, basement, topography. "
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Melnikov, R. V., and Y. A. Pronozin. "VERTICALITY OF BOREHOLES." Construction and Geotechnics 12, no. 3 (December 15, 2021): 94–104. http://dx.doi.org/10.15593/2224-9826/2021.3.10.
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The study contains the problem of the borehole shape of during drilling. Usage of a drilling bit and tubular or screw rods is traditional and most common drilling methods. The requirement of "verticality" for boreholes in the drilling process is necessary to comply with design solutions and design schemes. At the same time, the actual implementation of this important quality is often very difficult. An analysis of the regulatory documentation is carried out to ensure the requirement during conducting geotechnical investigations, and during installing pile foundations made in the ground: bored piles and continuous flight auger piles (CFA). Data about the researchers in the field of assessing of bending of the pile axis are presented for CFA piles. The article presents the results of field studies of the borehole verticality at two investigation sites. At the first site, a borehole was drilled with a depth of 9.0 m, at the second site, ten boreholes were drilled with a depth of 25.0 m. The spatial position of the boreholes was determined by an inclinometer. The results of the measured verticality deviations of the boreholes are presented on the spatial graph for clear visibility. A conclusion is made about the influence of the borehole shape on its vertical projection during conducting of geotechnical investigations. A series of comparative numerical calculations was performed using the Midas GTS NX program to assess the effect of the verticality deviations of the boreholes during installing bored piles on their bearing capacity. A single pile action in the ground was simulated for the pressing and pulling loads. It is concluded that the shape of the borehole influences on the single pile action in the ground.
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Feng, Renjun. "Influence of Long Boreholes Layout and Drilling Length on Gas Drainage Based on Multifield Coupling Model of Gas-Bearing Coal." Advances in Civil Engineering 2021 (November 17, 2021): 1–16. http://dx.doi.org/10.1155/2021/1473769.
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Gas drainage through long seam boreholes is an effective method to prevent gas disasters in coal mines. In this paper, a multifield coupling model of gas migration in gas-bearing coal was first established. Then, a quantitative characterization method of gas drainage effect was put forward. Finally, the extraction effect of long boreholes was obtained under different layouts and drilling lengths. The research results show that, under the arrangement of long boreholes along the seam, the gas pressure around the borehole decreases significantly with the extraction time. There is no extraction blank in the middle of the working face. However, it is easy to cause uneven gas drainage in the combined arrangement of the long boreholes along the seam and the penetrating boreholes. Furthermore, it is found that the drainage volume of the long boreholes along the seam is similar to that of the joint layout under the same drainage time. As the length of the borehole increases, the influencing range of gas drainage increases. When the borehole lengths are 150 m and 240 m, the drainage volumes are about 1.31 and 2.50 times that of the 90 m boreholes, respectively. The research achievements could provide a specific reference for the layout of long boreholes along the bedding and the determination of reasonable parameters for gas drainage on site.
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Ewusi, A., and J. Seidu. "Borehole Rehabilitation: A Case Study in the Dunkwa Mining Town." Ghana Mining Journal 20, no. 2 (December 31, 2020): 11–17. http://dx.doi.org/10.4314/gm.v20i2.2.
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Rehabilitation works were carried out on boreholes in the Dunkwa Mining town in the Central Region of Ghana. These works were carried out because the boreholes had lost their original yields due to clogging, corrosion and encrustation and had been abandoned for a long time. The cost of drilling a new well and assessing the productivity of the well is $4,500 which is more expensive that carrying out rehabilitation works which is cheaper, about $800. Also, the initial yields of the boreholes were very high according to the feasibility report which is not a common characteristic of the rocks in the area. Camera inspection followed by rehabilitation, pre and post pumping tests were carried out to assess whether there has been an improvement in their yield after the exercise and that the yield obtained will be adequate for a water supply design. Results show that all the boreholes had an improvement in their yields (57.19 - 259.80 %) after the rehabilitation. It can therefore be concluded that rehabilitation is effective in restoring boreholes to their original yields. Organisations drilling boreholes to communities can take advantage of rehabilitation of the existing boreholes located in the communities which are high yielding, thereby reducing project implementation cost.
Keywords: Borehole Rehabilitation, Borehole Yields, Borehole Camera Inspection, Pumping Test
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Wang, Yonglong, Zaijiang Yu, and Zhenfeng Wang. "A Mechanical Model of Gas Drainage Borehole Clogging under Confining Pressure and Its Application." Energies 11, no. 10 (October 18, 2018): 2817. http://dx.doi.org/10.3390/en11102817.
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Drilling in a coal seam that has gas and coal outburst activities is closely related to the discharge of drill cuttings into a borehole. Due to the low effectiveness of slagging, there is a risk that the drilling equipment will be lost if the borehole contains too many drill cuttings, especially when drilling in soft coal seams that suffer from borehole deformation and instability problems. In order to investigate the mechanisms underlying clogged boreholes, a mechanical model is established that considers the confining pressure pi that surrounds a borehole. The characteristics of clogged boreholes, which are affected by parameters such as the clogging segment’s length L, the drilling angle θ and confining pressure pi, were analyzed. The results show that the dredging pressure has nearly exponential growth as the clogging segment’s length L increases and the gravity of the clogging segment reduces the demand for dredging pressure, especially in upward drilling. In downward drilling, the blowing-through pressure increases as the absolute value of the drilling angle increases and will reach a maximum value when the drilling angle θD is in the range of −π/2~0. At the same time, the borehole’s confining pressure pi is the dominant factor in borehole clogging. Meanwhile, boreholes with a high confining pressure pi, especially in soft coal seams and coal seams with a coal outburst, constitute a significant risk. Finally, an actual drilling field construction was evaluated and optimized by applying the clogging segment mechanical model. The results show that the drilling depth was improved by 18.5% on average, and the drilling efficiency was improved by 39.7%, in comparison to drilling activities without optimization.
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Jiang, Guojing, Xiaomin Zhou, Fangzheng Li, Wei Gao, Jianrong Sun, Yufu Han, and Zhigang Yang. "Formula Development and Application of Wall Protection Slurry for Long-distance Horizontal Freezing Boreholes and Thorough Piles." E3S Web of Conferences 218 (2020): 03026. http://dx.doi.org/10.1051/e3sconf/202021803026.
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Since complex barriers need to be passed through during the process of drilling long-distance horizontal freezing boreholes, the stability of the borehole wall at the soft and hard stratum interface is the key in controlling the deflection of the horizontal boreholes. The author puts forward to establishing the stability mechanical model of horizontal freezing borehole walls with fluid loss as the control index, starting from the stability mechanism of horizontal freezing boreholes and combined with the working conditions of horizontal freezing boreholes; selects two optimal fluid loss additives from the perspective of the molecular structure of bentonite materials, and determines the optimal formula by formulation optimization by virtue of orthogonal tests; applies the optimal formula into the long-distance pile and borehole penetration test, and validates the reliability of wall protection slurry formula materials for horizontal boreholes via comparing the water loss and soil erosion at the pile interface and analyzing the deflection rules, which is of certain value in engineering promotion and application.
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Krukovska, Viktoriia, and Viktor Kocherha. "Influence of the method of gate road protection on the operating efficiency of methane drainage boreholes." IOP Conference Series: Earth and Environmental Science 970, no. 1 (January 1, 2022): 012045. http://dx.doi.org/10.1088/1755-1315/970/1/012045.
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Abstract Methods of numerical modelling have helped to carry out the research of coupled processes of rock deformation around a gate road with methane drainage boreholes and methane filtration in terms of applying different techniques of its protection. The following has been shown: without the use of protective structures, underworked drainage boreholes are broken and stop functioning. If the protective structures are used, the rock-bolting beam above the mined-out space becomes stable. Boreholes go beyond the zones of inelastic deformations and remain in their operating conditions even after their undermining by a stope. The yield of a methane-air mixture in two methane drainage boreholes increases that is confirmed by experimental data. The efficiency of roof degassing by boreholes when using the considered protective structures is 13-63%. The borehole position is of great importance for its operating efficiency. If the borehole is beyond the filtration area, methane yield is minimal. It is quite high within the zone of increased fissuring of host rocks. If the methane drainage borehole is near the zone of inelastic deformations, methane yield reaches its maximum, but reliability of borehole operation is not high. The borehole is broken within the zone of inelastic deformations.
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Xue, Fei, and Xiaowei Feng. "Spatial and Temporal Distribution Law and Influencing Factors of the Mining-Induced Deformation and Failure of Gas Boreholes." Advances in Materials Science and Engineering 2018 (August 15, 2018): 1–15. http://dx.doi.org/10.1155/2018/9580526.
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Because gas boreholes are easy to damage by integrated coal mining and gas exploration, based on the practice of relieving pressure in deep thin coal seams in the Huainan mining area, a multidimensional coupling numerical simulation method was used to reveal the space-time evolution characteristics and influence factors of fracture deformation of gob-side gas boreholes. Results indicate that the danger zone for borehole fractures is primarily between 5 and 12 m above the roof of the roadway. The final-hole position has little effect on the stability of boreholes, and migrating the open-hole position to the entity coal side and roadway roof side can improve the stability of the borehole. The initial failure of the borehole occurs at a distance of 10 m behind the coal face. The failure of the borehole is largely stable at a distance of 100 to 120 m behind the coal face. With the increase in mining height, which leads to an increase in the movement of strata and an increase in pressure relief range, the shear stability of the borehole is reduced, and the extrusion stability of the borehole is improved. A hard roof condition promotes borehole shear stability, while a weak roof condition promotes borehole extrusion stability. This change can decrease the maintenance difficulty associated with “minor supports” in boreholes to a certain extent by reinforcing the support strength of “primary supports” in roadway retaining walls. The simulation results are consistent with observed results for the 11 test boreholes, and the accuracy of the numerical simulation is verified.
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Zhang, Lei, Chen Jing, Shugang Li, Ruoyu Bao, and Tianjun Zhang. "Seepage Law of Nearly Flat Coal Seam Based on Three-Dimensional Structure of Borehole and the Deep Soft Rock Roadway Intersection." Energies 15, no. 14 (July 8, 2022): 5012. http://dx.doi.org/10.3390/en15145012.
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Exploring the evolution characteristics of gas seepage between boreholes during the drainage process is critical for the borehole’s layout and high-efficiency gas drainage. Based on the dual-porous medium assumption and considering the effect of stress redistribution on coal seam gas seepage characteristics, a coal seam gas seepage model with a three-dimensional roadway and borehole crossing structure has been established and numerically calculated, concluding that the coal seam is between the drainage boreholes. The temporal and spatial evolution characteristics of gas pressure and permeability help elucidate the gas seepage law of the nearly flat coal seam associated with the deep soft rock roadway and borehole intersection model. The results indicate that: (1) The roadway excavation results in localized stress in some areas of the surrounding rock, reducing the strength of the coal body, increasing the expansion stress, and increasing the adsorption of gas by the coal body. (2) Along the direction of the coal seam, the permeability decreases initially and then increases. The gas pressure in the coal seam area in the middle of the borehole is higher than the pressure in the coal seam around the borehole, and the expansion stress and deformation increase, reducing the permeability of the coal body; when near the next borehole, the greater the negative pressure, the faster the desorption of the gas attracts the matrix shrinkage effect and causes the coal seam permeability rate to keep increasing. (3) The improvement of gas drainage with the overlapping arrangement of two boreholes firstly increases and then decreases as time goes on. (4) When the field test results and numerical simulation of the effective area of gas extraction are compared, the effectiveness of the model is verified. Taking the change of the porosity and the permeability into the model, it is able to calculate the radius of gas drainage more accurately.
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Hwang, Seokhwa, Rin Yun, and Jaehyeok Heo. "Transient Modeling of Seasonal Borehole Thermal Energy Storage System During Heat Energy Storing Process." International Journal of Air-Conditioning and Refrigeration 28, no. 01 (March 2020): 2050005. http://dx.doi.org/10.1142/s2010132520500054.
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The borehole thermal energy system, KINTEX, located in Ilsan, South Korea was simulated using TRNSYS. The effect of the depth and spacing of the boreholes in this Borehole Thermal Energy Storage (BTES) system on the average stored energy and ground temperature were investigated over three years of its operation. Borehole thermal energy storage was simulated using the Duct Ground Heat Storage Model built in TRNSYS. The BTES system is composed of solar collectors, a heat exchanger, borehole thermal energy storage, and a thermal storage tank. The effects on the internal energy of the system were investigated by varying borehole depth and spacing while the volume and number of boreholes were kept constant. The total number of boreholes is 90 and all boreholes are connected in series. The borehole depths varied from 40 to 47.5[Formula: see text]m with steps of 2.5[Formula: see text]m, and the borehole spacing varied from 2.5 to 4.0[Formula: see text]m while the total volume of the BTES was maintained at 21,[Formula: see text]236 [Formula: see text]m3. The internal energy stored ranged from 1528.91 GJ to 1618.69 GJ over three years of calculations. With an increase of borehole depth and associated decrease of borehole spacing, the internal energy increased and ground temperatures approached 35∘C over a simulation period of three years.
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Robinson, Judith, Timothy Johnson, and Lee Slater. "Challenges and opportunities for fractured rock imaging using 3D cross-borehole electrical resistivity." GEOPHYSICS 80, no. 2 (March 1, 2015): E49—E61. http://dx.doi.org/10.1190/geo2014-0138.1.
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There is an increasing need to characterize discrete fractures away from boreholes to better define fracture distributions and monitor solute transport. We performed a 3D evaluation of static and time-lapse cross-borehole electrical resistivity tomography (ERT) data sets from a limestone quarry in which flow and transport are controlled by a bedding-plane feature. Ten boreholes were discretized using an unstructured tetrahedral mesh, and 2D panel measurements were inverted for a 3D distribution of conductivity. We evaluated the benefits of 3D versus 2.5D inversion of ERT data in fractured rock while including the use of borehole regularization disconnects (BRDs) and borehole conductivity constraints. High-conductivity halos (inversion artifacts) surrounding boreholes were removed in static images when BRDs and borehole conductivity constraints were implemented. Furthermore, applying these constraints focused transient changes in conductivity resulting from solute transport on the bedding plane, providing a more physically reasonable model for conductivity changes associated with solute transport at this fractured rock site. Assuming bedding-plane continuity between fractures identified in borehole televiewer data, we discretized a planar region between six boreholes and applied a fracture regularization disconnect (FRD). Although the FRD appropriately focused conductivity changes on the bedding plane, the conductivity distribution within the discretized fracture was nonunique and dependent on the starting homogeneous model conductivity. Synthetic studies performed to better explain field observations showed that inaccurate electrode locations in boreholes resulted in low-conductivity halos surrounding borehole locations. These synthetic studies also showed that the recovery of the true conductivity within an FRD depended on the conductivity contrast between the host rock and fractures. Our findings revealed that the potential exists to improve imaging of fractured rock through 3D inversion and accurate modeling of boreholes. However, deregularization of localized features can result in significant electrical conductivity artifacts, especially when representing features with a high degree of spatial uncertainty.
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Gonet, Andrzej. "Optimization of a Directional Borehole Trajectory as the Criterion of Minimum Cost of Performance / Optymalizacja Trajektorii Otworu Kierunkowego Dla Kryterium Minimalizacji Kosztu Jego Wykonania." Archives of Mining Sciences 57, no. 4 (December 1, 2012): 901–10. http://dx.doi.org/10.2478/v10267-012-0059-5.
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Abstract New drilling technical and technological solutions enhance the development of directional drilling, enabling better control of direction of drilling and real-time 3D information about the position of the bit in the borehole rendered by the control and measurement apparatuses. The 2D and 3D method of designing the trajectory of a borehole axis has been modified in this paper. In both cases the minimum cost of drilling of a borehole in an interval from the beginning of its deflecting (KOP) up to the ultimate destination point was assumed to be the optimization criterion. Another assumption says that the admissible dogleg will never be exceeded over the entire interval of the borehole axis. Commonly more and more boreholes are performed from one place or one drilling platform. Such drilling is aimed at, e.g. developing unconventional deposits of natural gas or improving the depletion factor by injecting water or CO2. In such cases the boreholes are located densely, which may result in their colliding. Hence, attention was drawn to the fact that in such cases inaccuracies of apparatuses measuring the angle of deflection of the borehole, azimuth, length of the borehole and formation of error ellipsoids around a given point should be accounted for. The assumed method of positioning the borehole axis is also important. For a considerable length of the borehole axis the calculations are simple but time-consuming, therefore specialist computer programs are recommended. The trajectories of directional boreholes should be designed taking into account the position of the neighboring boreholes and inaccuracy of measuring equipment, as in this way the level of risk of potential collisions of boreholes axes can be determined.
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Siwila, Stephen, and Choolwe Buumba. "Investigation of groundwater contamination in relation to septic systems in Kitwe West Township, Kitwe, Zambia." Water Science and Technology 84, no. 10-11 (October 8, 2021): 3277–85. http://dx.doi.org/10.2166/wst.2021.448.
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Abstract This study investigated the quality of groundwater with respect to septic systems in Kitwe West township located in the western part of Zambia's Kitwe district. The study area was selected because most households in the township use boreholes and septic systems as sources of drinking water and wastewater disposal facilities respectively. The study showed the presence of total coliforms in 90% of the boreholes while only 30% of the boreholes were contaminated with fecal coliforms rendering the water unsafe for drinking. The study revealed that there was no distinct relationship between distance from borehole to septic tank system and the quality of borehole water. It was however observed that for boreholes within a 15 m proximity to individual home-owned dump sites the level of fecal contamination increased as the distance from the boreholes to the dump sites decreased. The study has vividly shown that the location of boreholes and septic tank systems in the same plot of land exacerbated by the presence of solid waste dump sites in a residential plot that depends on groundwater is not advisable. This is because the safety of groundwater cannot be guaranteed even if technical specifications are followed for boreholes and septic tank systems.
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Liu, Sixin, and Motoyuki Sato. "Transient radiation from an unloaded, finite dipole antenna in a borehole: Experimental and numerical results." GEOPHYSICS 70, no. 6 (November 2005): K43—K51. http://dx.doi.org/10.1190/1.2106048.
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Dipole antennas in boreholes are used for tomographic imaging or electromagnetic well logging. A cylindrically layered structure within the borehole will change the radiation characteristics of a dipole antenna. Our objective is to understand the effects of the borehole structure upon the impedance, waveform distortion, and directivity patterns of a dipole antenna. We use a finite-difference, time-domain (FDTD) technique to simulate borehole-antenna radiation, while the geometry of both the dipole and the borehole are modeled with a subgrid technique. The simulated input impedances are verified by experimental results. Both the water-filled and the air-filled boreholes distort the radiated wavefronts, waveforms, and resonant frequencies relative to the same characteristics of a dipole in homogeneous media. A water-filled borehole lowers the first resonant frequency, while an air-filled borehole raises it. At high frequencies, the antenna in the water-filled borehole exhibits radiation side lobes. The borehole effects for water- and air-filled boreholes differ and should not be neglected for borehole antenna design.
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Ilisei, Gheorghe, Tiberiu Catalina, and Robert Gavriliuc. "Sensitivity analysis using simulations for a ground source heat pump – implementation on a solar passive house." E3S Web of Conferences 111 (2019): 01070. http://dx.doi.org/10.1051/e3sconf/201911101070.
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Having in sight the need for a strong reduction in CO2 emissions and the fluctuation of the price of fossil fuels, the ground source resources alongside with the ground source heat pumps are becoming more and more widespread for meeting the heating/cooling demand of several types of buildings. This article targets to develop the thermal modelling of borehole heat storage systems. Trying to emphasize some certain advantages of a GSHP (ground source heat pump) with vertical boreholes, a case study analysing a residential solar passive house is presented. The numerical results are produced using different modelling software like DesignBuilder, EED (Earth Energy Designer) and a sizing method for the length of the boreholes (ASHRAE method). The idea of sizing the length of boreholes (main design parameter and good index in estimating the system’s cost) using two different methods shows the reliability of this modelling tool. The study shows that borehole’s length of a GSHP system can trigger a difference in electricity consumption up to 22%. Moreover, this sensitivity analysis aims to prove that the design of the whole system can be done beforehand just using modeling tools, without performing tests in-situ.
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Shuang, Haiqing, Weitao Meng, Yulong Zhai, Peng Xiao, Yu Shi, and Yu Tian. "Application and Optimization of the Parameters of the High-Level Boreholes in Lateral High Drainage Roadway." Sustainability 14, no. 24 (December 16, 2022): 16908. http://dx.doi.org/10.3390/su142416908.
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The key parameters of high-level boreholes in high drainage roadways affect the gas treatment effect of the working face directly. Therefore, the layout parameters of high-level boreholes in the lateral high drainage roadway (LHDR) are determined and optimized as necessary. Based on the LHDR layout on the 2-603 working face of the Liyazhuang coal mine, the key technological requirements on high-level borehole parameters were analyzed and the distribution characteristics of the gas volume fraction in the coal roof were studied. The gas migration law in the mined-out areas was obtained and the layout locations of high-level boreholes were determined finally. The research demonstrates that the high-level boreholes lag the 2-603 working face distance and the position of the final borehole (the position of the final borehole in this paper refers to the distance between the final borehole and the roof) influence the stability of boreholes and the gas extraction effect. The distribution of the gas volume fraction from the intake airway to the return airway can be divided into the stable stage, slow growth stage, and fast growth stage. Influenced by the flow field in the mined-out areas, the mean volume fraction of the borehole-extracted gas has no obvious relationship with the gas volume fraction at the upper corner. According to the final optimization, the high-level borehole is determined as having a 15 m lag behind the working face and the position of the final borehole is 44 m away from the coal seam roof. These have been applied successfully in engineering practice.
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Smetanová, I., K. Holý, M. Müllerová, A. Polášková, and I. Túnyi. "Temporal and spatial changes of radon concentration in borehole water (Little Carpathians Mts., Slovakia)." Natural Hazards and Earth System Sciences 10, no. 7 (July 1, 2010): 1373–77. http://dx.doi.org/10.5194/nhess-10-1373-2010.
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Abstract. The 222Rn activity concentration in ground water from four boreholes was investigated from January 2006 to June 2008. The boreholes are situated in the region of the Astronomical and Geophysical Observatory in Modra-Piesok (Little Carpathians Mts., 40 km NW from Bratislava, Slovakia). Three boreholes have been drilled in Lower Triassic quartzite. Another borehole has been drilled in granodiorite of the Modra massif in which the quartzite is folded. Temporal and spatial differences in radon concentration were observed. Significant short-term variations were noticed in all boreholes. Precipitation caused the changes of water level and strongly affected the values of 222Rn activity concentration in less deep boreholes. The measured activities in boreholes ranged approximately over 1–240 kBq/m3.
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Hao, Zhen, Guangzhong Sun, Haihang Wei, Jiayu Liu, Maolin Tian, Shuaiyi Liu, and Yikun Xu. "Pressure-Relief Mechanism and Application of Large-Diameter Boreholes in Coal Seams with Rockburst Hazard." Geofluids 2021 (October 7, 2021): 1–9. http://dx.doi.org/10.1155/2021/5469999.
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Drilling of large-diameter boreholes is regarded as an effective measure for rockburst prevention. By investigating the morphological characteristic and evolution of plastic zone in borehole surrounding rock, the pressure-relief mechanism of large-diameter borehole was ascertained, and the engineering application of large-diameter boreholes was assessed in the 13230 working face of Gengcun Coal Mine, Henan Province, China. The results showed that (1) the plastic zone in surrounding rock of borehole appear as circular, elliptical, and butterfly shapes, in which the maximum size of the butterfly wings of the plastic zone is several times larger than the borehole diameter; (2) under certain stress conditions, multiple large-diameter boreholes distributed in coal seam with rockburst risk lead to the generation and coalescence of large-range butterfly-shape plastic zone. They reduce the stress concentration and capacity for storing elastic energy of coal seam, thus reducing the rockburst risk of the coal seam; (3) large-diameter boreholes significantly decrease the stress concentration in front of the 13230 working face and improve the stress environment in the head entry, promoting the safe mining of the working face.
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Li, Gang, and Jiafei Teng. "Research and Optimization of Gas Extraction by Crossing-Seam Boreholes from Floor Roadway." Geofluids 2021 (August 9, 2021): 1–10. http://dx.doi.org/10.1155/2021/7499012.
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Deep coal seams are characterized by large stress, high gas pressure, and low permeability. The gas disaster threatens the safe production of coal mine seriously. Gas extraction by crossing-seam boreholes from floor roadway (GECMBFR) can reduce the pressure and content of coal seam gas, which is the main measure to prevent gas disaster. Considering the Klinkenberg effect, governing equations of gas adsorption/desorption-diffusion, gas seepage, and stress fields within the coal seam are established to form the seepage-stress coupling model. The governing equations are embodied into a finite element driven software to numerically simulate gas migration and fluid-solid coupling law in coal seam. On this basis, the process of gas extraction under different borehole spacings and diameters is simulated. The effects of these two key parameters on coal seam gas pressure, gas content, and gas permeability were analyzed. The borehole spacing and diameter were determined to be 5 m and 0.09 m, respectively. Combined with the actual situation of a mine, the process of gas extraction from floor roadway with different cross-sectional schemes, ordinary drilling boreholes and punching combined drilling boreholes, is comparatively analyzed. The results show that the gas extraction effect by ordinary drilling boreholes is lower than that of the punching combined drilling boreholes, and the extraction is uneven and makes it difficult to meet the standard. Hydraulic punching was carried out, and coal was washed out of the borehole, which expanded the contact area between the borehole wall and coal seam. The coal seam around the punching borehole is unloaded, which improves coal permeability and accelerates gas migration towards the borehole, thus promoting the efficiency of gas extraction. It is more reasonable to use punching combined drilling borehole scheme when implementing the GECMBFR technology.
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Dong, Wenjie, and M. Nafi Toksöz. "Borehole seismic‐source radiation in layered isotropic and anisotropic media: Real data analysis." GEOPHYSICS 60, no. 3 (May 1995): 748–57. http://dx.doi.org/10.1190/1.1443813.
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The source and receiver boreholes in crosshole seismology are usually considered unimportant except for their effects on body wave radiation and reception patterns. We present counter examples by analyzing a real crosswell data set from Buckhorn, Illinois, using computer simulations. The algorithm used is a combination of the boundary element method (for the source borehole) and the borehole coupling theory (for the receiver borehole) in transversely isotropic media. We find that most of the strong events in the data are inexplicable unless both boreholes are included in the modeling. The importance of the boreholes stems from the local geology which consists of highly contrasted sedimentary rocks. At a high‐contrast interface, wave conversion is no longer a negligible secondary effect. In fact, converted waves can be stronger than the primaries.
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Zhu, Zhenya, and M. Nafi Toksöz. "Crosshole seismoelectric measurements in borehole models with fractures." GEOPHYSICS 68, no. 5 (September 2003): 1519–24. http://dx.doi.org/10.1190/1.1620625.
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Laboratory experiments are performed in cross‐borehole models with fractures to investigate seismoelectric conversions in the fractures. Using an electrode in a borehole, we measure the electric field induced by an acoustic wave, and we investigate the relationship between the electric signal and the fracture aperture using ultrasonic fracture borehole models. The experimental results confirm that a radiating electromagnetic (EM) wave is induced by a guide wave at a fracture between an acoustic source and electric receiver boreholes. The position of a vertical or inclined fracture between two boreholes can be determined using the arrival times of the EM wave and the formation velocity by placing the acoustic source at a different depth and recording electric signals with real or synthetic arrays of acoustic and electric receivers in the second borehole. Crosshole seismoelectric measurements might be a technique for investigating fractures between boreholes more directly than traditional acoustic measurements.
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Todorov, Oleg, Kari Alanne, Markku Virtanen, and Risto Kosonen. "Different Approaches for Evaluation and Modeling of the Effective Thermal Resistance of Groundwater-Filled Boreholes." Energies 14, no. 21 (October 21, 2021): 6908. http://dx.doi.org/10.3390/en14216908.
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Groundwater-filled boreholes are a common solution in Scandinavian installations of ground source heat pumps (GSHP) due to the particular hydro-geological conditions with existing bedrock, and groundwater levels close to the surface. Different studies have highlighted the advantage of water-filled boreholes compared with their grouted counterparts since the natural convection of water within the borehole tends to decrease the effective thermal resistance Rb*. In this study, several methods are proposed for the evaluation and modeling of the effective thermal resistance of groundwater-filled boreholes. They are based on distributed temperature sensing (DTS) measurements of six representative boreholes within the irregular 74-single-U 300 m-deep borehole field of Aalto New Campus Complex (ANCC). These methods are compared with the recently developed correlations for groundwater-filled boreholes, which are implemented within the python-based simulation toolbox Pygfunction. The results from the enhanced Pygfunction simulation with daily update of Rb* show very good agreement with the measured mean fluid temperature of the first 39 months of system operation (March 2018–May 2021). It is observed that in real operation the effective thermal resistance Rb* can vary significantly, and therefore it is concluded that the update of Rb* is crucial for a reliable long-term simulation of groundwater-filled boreholes.
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Weidenfeller, Michael, and Maria Knipping. "Correlation of Pleistocene sediments from boreholes in the Ludwigshafen area, western Heidelberg Basin." E&G Quaternary Science Journal 57, no. 3/4 (April 1, 2009): 270–85. http://dx.doi.org/10.3285/eg.57.3-4.1.
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Abstract. Cores from several boreholes in the Ludwigshafen area were analysed to investigate their sedimentology, palynology, palaeomagnetics, rock magnetics and heavy mineral composition. The preliminary results are presented from the new Ludwigshafen-Parkinsel borehole P35, which was drilled 500 m WSW of borehole P34, to a total depth of 300 m. Correlation between the two boreholes reveals similarities and dissimilarities in stratigraphy, structure and the thickness of the sediments. As a result of core documentation and the preliminary evaluation of the investigation results, a good correlation is established between the coarse and fi ne-grained sequences in both boreholes down to a depth of 122 m. However, the Plio-Pleistocene boundary in borehole P35 is much deeper than in P34. A fault throw of 42 m is assumed, attributable to young tectonics. The poor correlation between the thicknesses of the sediments in the lower sections of the two boreholes suggests that tectonism was particularly active in the Pliocene and Lower Pleistocene. The different occurrence of interglacial sequences in the two Ludwigshafen boreholes can be attributed to fl uvial dynamics and neotectonic events. Further palynological analysis is required to determine whether the alternation of at least fi ve interglacial periods determined in the Ludwigshafen-Parkinsel P34 borehole, can also be confi rmed in the P35 borehole. The information gained so far from the correlation of the already analysed Middle Pleistocene interglacials in the Ludwigshafen/Mannheim area, as well as the links with the primarily Lower Pleistocene sections in Schifferstadt, already suggest that this would allow a much better understanding of the changes in vegetation and climate during the Pleistocene.
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Onyemaechi, Okezie, and Nwachukwu Ejikeme. "Seasonal Dynamics of the Microbial and Physicochemical Characteristics of Streams and Boreholes in Uzuakoli, Eastern Nigeria." Journal of Biology and Life Science 10, no. 2 (March 5, 2019): 17. http://dx.doi.org/10.5296/jbls.v10i2.14456.
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Water samples from twenty water sources (fifteen boreholes and five streams) in Uzuakoli, Nigeria were collected for the period of 6 months covering the dry and rainy seasons to assess the level of contamination. The Microbiological characteristics including heterotrophic counts, coliform counts and physicochemical parameters includes pH, turbidity, dissolved oxygen, calcium, potassium, nitrate, magnesium and phosphate were evaluated using standard methods. The total Heterotrophic counts for the borehole during the dry and rainy season were 8.3 x 103 cfu/ ml and 10.8 x 104 cfu/ ml. The Heterotrophic counts for the stream were 12.7 x 104 cfu/ ml and 17.8x 106 cfu/ ml. The frequency of occurrence of the isolates are Staphylococcus aureus 63% in borehole and 85% in streams, Pseudomonas aeruginosa 49% in boreholes and 95% in streams, Proteus sp 52% in boreholes and 97% in streams, Streptococcus sp 46% in boreholes and 53% in streams, Enterobacter aerogenes 33% in boreholes and 63% in streams, Escherichia coli 16% in boreholes and 53% in streams and Salmonella sp no percentage in boreholes and 40% in streams. The result shows a significant difference at (P≤0.05) for the bacterial isolates. The physicochemical parameters of the borehole and stream water samples during the dry and rainy seasons were determined. The temperature ranged from 25oC 32oC; pH ranged from 5.3 8.1; turbidity ranged 0.03 3.23; dissolved oxygen ranged from 3.45–7.40mg/l; biochemical oxygen demand ranged from 1.20–4.32mg/l; chemical oxygen demand ranged from 2.50–5.21mg/l; Calcium ranged from 0.81–5.64mg/l; potassium ranged from 1.01–4.22mg/l; Nitrate ranged from 1.49–4.02mg/l; magnesium ranged from 0.13–2.20mg/l; phosphate ranged from 0.51–2.01mg/l. The water samples were all within the WHO limits apart from sample from Iyi Agbozu that had temperature of 32oC.
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Badura, Henryk, and Zygmunt Łukaszczyk. "Analysis of Exploitation Parameters in Drainage Boreholes of the Longwall Demethylation System. Case Study." Multidisciplinary Aspects of Production Engineering 4, no. 1 (September 1, 2021): 23–39. http://dx.doi.org/10.2478/mape-2021-0003.
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Abstract In hard coal mines with methane, there is often a need to apply demethylation in order to keep the methane concentration not exceeding 2% in the ventilation air. The basic demethylation method in longwall areas is through drainage boreholes made in the roof rocks of the coal bed, from top gate, in front of the longwall. The drainage boreholes are usually made in bundles, in a fan-shaped arrangement, with several boreholes in each bundle. The paper presents the results of measurements and tests of the efficiency of a bundle of four drainage boreholes drilled approximately 100 m in front of the longwall face. The efficiency of individual boreholes was analyzed in time and depending on the distance of borehole outlets from the longwall face. It was found that there is a large variation in the extraction of air-methane mixture by individual drainage boreholes, as well as large differences in the efficiency of individual drainage boreholes during the longwall extraction process.
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Fischer, Tomáš, Pavla Hrubcová, Torsten Dahm, Heiko Woith, Tomáš Vylita, Matthias Ohrnberger, Josef Vlček, et al. "ICDP drilling of the Eger Rift observatory: magmatic fluids driving the earthquake swarms and deep biosphere." Scientific Drilling 31 (October 28, 2022): 31–49. http://dx.doi.org/10.5194/sd-31-31-2022.
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Abstract. The new in situ geodynamic laboratory established in the framework of the ICDP Eger project aims to develop the most modern, comprehensive, multiparameter laboratory at depth for studying earthquake swarms, crustal fluid flow, mantle-derived CO2 and helium degassing, and processes of the deep biosphere. In order to reach a new level of high-frequency, near-source and multiparameter observation of earthquake swarms and related phenomena, such a laboratory comprises a set of shallow boreholes with high-frequency 3-D seismic arrays as well as modern continuous real-time fluid monitoring at depth and the study of the deep biosphere. This laboratory is located in the western part of the Eger Rift at the border of the Czech Republic and Germany (in the West Bohemia–Vogtland geodynamic region) and comprises a set of five boreholes around the seismoactive zone. To date, all monitoring boreholes have been drilled. This includes the seismic monitoring boreholes S1, S2 and S3 in the crystalline units north and east of the major Nový Kostel seismogenic zone, borehole F3 in the Hartoušov mofette field and borehole S4 in the newly discovered Bažina maar near Libá. Supplementary borehole P1 is being prepared in the Neualbenreuth maar for paleoclimate and biological research. At each of these sites, a borehole broadband seismometer will be installed, and sites S1, S2 and S3 will also host a 3-D seismic array composed of a vertical geophone chain and surface seismic array. Seismic instrumenting has been completed in the S1 borehole and is in preparation in the remaining four monitoring boreholes. The continuous fluid monitoring site of Hartoušov includes three boreholes, F1, F2 and F3, and a pilot monitoring phase is underway. The laboratory also enables one to analyze microbial activity at CO2 mofettes and maar structures in the context of changes in habitats. The drillings into the maar volcanoes contribute to a better understanding of the Quaternary paleoclimate and volcanic activity.
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Xu, Hongjie, Zezhong Fang, Shuxun Sang, Huihu Liu, Hai Ding, Xinzhao Dou, and Qinjie Liu. "Analysis of the shear failure of surface methane capture boreholes for improving the drainage period efficiency: A lithological perspective." Energy Exploration & Exploitation 38, no. 1 (October 22, 2019): 92–110. http://dx.doi.org/10.1177/0144598719884671.
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The shear failure of surface methane capture boreholes (SMCBs) is the main reason for the life cycle shortening of surface methane capture boreholes but lacks a comprehensive lithological analysis. To improve the surface methane capture borehole stability and drainage period efficiency, it is of great importance to investigate the influence of lithology on the shear failure of surface methane capture boreholes. The results of direct shear tests and geological investigations show that the shear displacement increases as the grain size decreases. A jump in mechanical properties occurs at the lithological boundaries and is mainly controlled by the composition of the rock specimens. The change in cohesion is the main possible reason for the step change of the shear strength. High quartz and low clay contents may effectively improve the shear strength and failure resistance of rock. Boreholes may potentially experience preferential casing failure in the section of the weaker mudstone and siltstone due to larger shear displacements and lower shear strengths of those rock types. Protective measures at these sections may improve the stability of the borehole casing. The detection results at the close of the borehole verify the prediction.
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Liu, Haibo, Zhihang Shu, Yinbin Shi, Xuebing Wang, Xucheng Xiao, and Jia Lin. "Gas Migration Patterns with Different Borehole Sizes in Underground Coal Seams: Numerical Simulations and Field Observations." Minerals 11, no. 11 (November 11, 2021): 1254. http://dx.doi.org/10.3390/min11111254.
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Gas flow in a coal seam is a complex process due to the complicated coal structure and the sorption characteristics of coal to adsorbable gas (such as carbon dioxide and methane). It is essential to understand the gas migration patterns for different fields of engineering, such as CBM exploitation, underground coal mine gas drainage, and CO2 geo-sequestration. Many factors influence gas migration patterns. From the surface production wells, the in-seam patterns of gas content cannot be quantified, and it is difficult to predict the total gas production time. In order to understand the gas flow patterns during gas recovery and the gas content variations with respect to production time, a solid-fluid coupled gas migration model is proposed to illustrate the gas flow in a coal seam. Field data was collected and simulation parameters were obtained. Based on this model, different scenarios with different borehole sizes were simulated for both directional boreholes and normal parallel boreholes in coal seams. Specifically, the borehole sizes for the directional boreholes were 10 m, 15 m, and 20 m. The borehole sizes for the normal parallel boreholes were 2 m, 4 m, and 6 m. Under different gas drainage leading times, the total gas recovery and residual gas contents were quantified. In Longwall Panel 909 of the Wuhushan coal mine, one gas drainage borehole and five 4 m monitoring boreholes were drilled. After six months of monitoring, the residual gas content was obtained and compared with the simulation results. Of the total gas, 61.36% was drained out from the first 4 m borehole. In this field study, the effective drainage diameter of the drainage borehole was less than 8 m after six months of drainage. The gas drainage performance was tightly affected by the borehole size and the gas drainage time. It was determined that the field observations were in line with the simulation results. The findings of this study can provide field data for similar conditions.
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Kiplangat, Alice S., Henry Mwangi, Sauda Swaleh, and Wilson M. Njue. "Arsenic Contamination in Water from Selected Boreholes in Nairobi City County, Kenya." European Journal of Advanced Chemistry Research 2, no. 2 (March 16, 2021): 1–6. http://dx.doi.org/10.24018/ejchem.2021.2.2.50.
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Arsenic is a metalloid, which may be found in surface water, ground water, plants and rocks. In high concentrations, its compounds are considered to be genotoxic and carcinogenic. Its levels in drinking water must be regularly monitored and controlled. The objective of study was to determine the concentration of arsenic in water with reference to WHO limits from selected boreholes in Nairobi County, Kenya. Water was randomly sampled from a total of 63 boreholes in five zones (Central, Eastern, Northern, Western and Southern) during dry and wet season. The arsenic was analyzed by Hydride Generation Atomic Absorption Spectrometer (HG-AAS). The results showed that the arsenic content in borehole water during dry season ranged between 0.00455±0.0022 and 0.01007±0.006 and in the range of 0.002057±0.0008 - 0.00744±0.0051 mg/L during the wet season. There was significant difference (P˂0.05) in arsenic content in borehole water samples in Central zone compared to the other zones. During the dry season, arsenic content in water from ten boreholes (16%) and four boreholes (6%) during wet season was found to be above the WHO recommended limit of 0.01 mg/L. The calculated contamination factor for the borehole water ranged from slightly arsenic contaminated in Central zone to very slightly contaminated in the other zones during dry season. During the wet season, the borehole water in all the five zones were very slightly contaminated with arsenic. The pollution index showed that the boreholes in all the five zones during both wet and dry seasons were not polluted with arsenic. Steps should be taken to monitor and treat borehole water for domestic purposes in order to mitigate the effect on human health due to arsenic contamination.
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Ewusi, A., and J. Seidu. "Efficacy of Geophysical Techniques for Groundwater Exploration in the Volta Basin, Northern Region of Ghana." Ghana Mining Journal 20, no. 1 (July 7, 2020): 11–19. http://dx.doi.org/10.4314/gm.v20i1.2.
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Abstract
Groundwater, traditionally extracted from hand-dug wells and boreholes is the main drinking water source in the Northern Region of Ghana. Many boreholes have been constructed in the region to increase accessibility to potable water mainly as part of rural water supply projects where borehole siting has to be relatively cheaper. These projects have resulted in low success rates of borehole drilling because of the application of inefficient and simple geophysical techniques supposed to be cheaper. Field surveys were conducted with the Electrical Resistivity Imaging (ERI) technique, Electrokinetic System (EKS) sounding technique and Radon (222Rn) technique with the objectives of determining the best geophysical methods for borehole siting and its efficiency in the Volta Basin (VB) in the Northern Region of Ghana. The surveys were conducted at stations of existing dry and positive boreholes. Results show that the three geophysical techniques are efficient to identify groundwater accumulation zones. The ERI, EKS and 222Rn are efficient to identify discontinuities, calculate hydraulic conductivity of discontinuities and identify areas of water circulation respectively. It is recommended that the ERI be used to obtain discontinuities and weak zones for drilling on rural water supply projects in the VB. The EKS and 222Rn should be conducted to evaluate these features when high yield boreholes are required.
Keywords: Geophysical Techniques, Volta Basin, Borehole Drilling, Success Rates
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Anyanwu, Ifeanyi Emmanuel, and Sodiq Solagbade Oguntade. "Groundwater exploitation in Awka (Anambra – Nigeria) and environs: Prospects, and challenges while drilling and its mitigation measures." Acque Sotterranee - Italian Journal of Groundwater 10, no. 4 (December 23, 2021): 27–33. http://dx.doi.org/10.7343/as-2021-528.
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Groundwater exploitation (borehole drilling) was carried out around Awka and environs in Anambra State, Southeastern Nigeria, to understand the underlying rock units encountered while drilling, differentiate boreholes with confined aquifers from those with unconfined aquifers, delineate the probable aquiferous zones from the borehole data, evaluate the challenges encountered while drilling (both geologic and technical), and identify mitigation measures employed to address these challenges. Detailed geologic log information of the boreholes was produced to illustrate the rock units encountered while drilling. Four rock units were identified, namely: shale, sandstone, clay, and gravel. These rock units were exposed within the Imo Formation and the Nanka Formation that underlie the study area. Results from the geologic log information of the boreholes indicate that the water table within the study area ranges from 11.2 m to 56.5 m from the soil surface, and the probable aquiferous zones vary from 6.8 m to 23.3 m in thickness. A detailed look at the lithologic logs of the boreholes show that 50% of the drilled boreholes possess confined aquifers while the remaining 50% have unconfined aquifers. A careful appraisal of the challenges encountered, which are mainly geologic, is strictly attributed to the geologic formation of the study area. Other technical challenges have been derived from mechanical faults developed during drilling.
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Taonameso, S., L. S. Mudau, A. N. Traoré, and N. Potgieter. "Borehole water: a potential health risk to rural communities in South Africa." Water Supply 19, no. 1 (March 19, 2018): 128–36. http://dx.doi.org/10.2166/ws.2018.030.
Full textAbstract:
Abstract Sporadic outbreaks of diarrhoea in children in the Vhembe rural areas could be an indication of contamination in drinking water sources. In areas where improved water sources are used, not all rural households experience the benefits of these improved water sources. Water samples were collected from boreholes in three wards in the Vhembe District to determine microbiological risks over a 5-month period. A Water Point Mapping tool was used to indicate the borehole distribution. Water samples were taken from each functional borehole and analysed for total coliform and Escherichia coli counts, electrical conductivity, pH and temperature. A multiplex PCR protocol was used for identification of pathogenic E. coli. A total of 125 boreholes were identified of which only 12 were functional. Seven boreholes tested positive for total coliforms and E. coli counts. Four boreholes (33.3%) tested positive for diarrhoeagenic E. coli. Fifty-eight percent (58%) of water samples were without health risks, 17% were low risk and 25% could cause infection according to the South African water quality standards. This study indicated the importance of the role of the Municipalities and the maintenance plans that need to ensure that all boreholes are functional and provide safe drinking water to the rural communities.
40
Kulessa, Bernd, and Bryn Hubbard. "Interpretation of borehole impulse tests at Haut Glacier d’Arolla, Switzerland." Annals of Glaciology 24 (1997): 397–402. http://dx.doi.org/10.3189/s0260305500012507.
Full textAbstract:
One hundred and sixteen impulse tests were conducted in a dense borehole array at Haut Glacier d’Arolla, Switzerland, during July and August 1995. Impulse-test response pressure oscillations reveal marked variations in three parameters: relative amplitude decay, oscillation frequency and net water-level displacement. Analysis of response signals from water-filled boreholes indicates that (i) responses from individual boreholes are reproducible over some tens of minutes; (ii) responses are similar, but not identical, for slug insertion (“slug tests”) and removal (“bail tests”); (iii) signal amplitude decay varies with the depth at which the recording pressure transducer is located in a borehole; and (iv) coherent minima in all three response parameters coincide with the location of a known preferential, subglacial water-flow pathway. This correspondence suggests, first, that water-filled and non-fluctuating boreholes have established a link to the subglacial aquifer at Haut Glacier d’Arolla and, secondly, that locally transmissive basal sediments may be identified by relatively low response-signal frequencies, response-signal decays and net water-level displacements. Impulse testing water-filled boreholes therefore has the capacity to provide information relating to the local hydrogeological properties of subglacial aquifers.In 43 cases, water levels in boreholes adjacent to those being tested were recorded in order to identify possible subglacial linkages. No such connections were detected.
41
Smart, C. C., and D. B. Ketterling. "A low-cost electrical conductivity profiler for glacier boreholes." Journal of Glaciology 43, no. 144 (1997): 365–69. http://dx.doi.org/10.1017/s0022143000003324.
Full textAbstract:
AbstractElectrical conductivity profiling allows definition of the hydrology of glacier boreholes occupied by contrasting water types. An inexpensive, robust conductivity profiling system is described that allows detailed description of borehole hydrostratigraphy with reasonable reproducibility. Field dato demonstrate the need to distinguish betweenbottom waterin boreholes andbasal waterin drainage systems at the glacier bed.
42
Du, Feng, Weilong Cui, and Kai Wang. "Study on Gas Migration Mechanism and Multi-Borehole Spacing Optimization in Coal under Negative Pressure Extraction." Processes 11, no. 1 (January 13, 2023): 259. http://dx.doi.org/10.3390/pr11010259.
Full textAbstract:
In order to study the gas migration in gas-bearing coal, and reasonably arrange gas drainage boreholes to improve the efficiency of gas drainage, a gas-solid coupling model is established based on the pore-fracture dual medium porous model. The solid deformation of coal body, gas seepage and diffusion, and gas adsorption and desorption are considered in this model. The COMSOL software is used to simulate the gas change in the coal matrix and coal fracture under single borehole extraction. We analyze the effective extraction range and study the migration mechanism of gas between coal fracture and borehole, coal matrix and coal fracture, and coal matrix. The effective extraction area of multi-borehole negative pressure gas extraction varies with extraction time and borehole spacing. At 140 d, the effective extraction radius is r = 1.3 m, and the spacing of boreholes is 233 r=1.5 m, 2 r=2.6 m,4 m,5 m,and 6 m, respectively. The influence of the equilateral triangle shape of three boreholes on the gas extraction effect is studied. The simulation results show that when three boreholes are extracted for 140 days under different borehole spacing, different gas extraction effects will be affected by a superposition effect. Considering the change in gas pressure, the effect of gas extraction in the effective extraction area, and the safety and cost performance of gas extraction, it is concluded that the optimal hole spacing is 5 m around 140 d. This study aims to provide reference for underground gas drilling layout and reasonable hole spacing.
43
Robinson, Judith, Timothy Johnson, and Lee Slater. "Evaluation of known-boundary and resistivity constraints for improving cross-borehole DC electrical resistivity imaging of discrete fractures." GEOPHYSICS 78, no. 3 (May 1, 2013): D115—D127. http://dx.doi.org/10.1190/geo2012-0333.1.
Full textAbstract:
There is a need to better characterize discrete fractures in contaminated hard rock aquifers to determine the fate of remediation injections away from boreholes and also to evaluate hydraulic fracturing performance. A synthetic cross-borehole electrical resistivity study was conducted assuming a discrete fracture model of an existing contaminated site with known fracture locations. Four boreholes and two discrete fracture zones, assumed to be the dominant electrical and hydraulically conductive pathways, were explicitly modeled within an unstructured tetrahedral mesh. We first evaluated different regularization constraints starting with an uninformed smoothness-constrained inversion, to which a priori information was incrementally added. We found major improvements when (1) smoothness regularization constraints were relaxed (or disconnected) along boreholes and fractures, (2) a homogeneous conductivity was assumed along boreholes, and (3) borehole conductivity constraints that could be determined from a specific conductance log were applied. We also evaluated the effect of including borehole packers on fracture zone model recovery. We found that the fracture zone conductivities with the inclusion of packers were comparable to similar trials excluding the use of packers regardless of electrical potential changes. The misplacement of fracture regularization disconnects (FRDs) can easily be misinterpreted as actual fracture locations. Conductivities within these misplaced disconnects were near the starting model value, and removing smoothing between boreholes and assumed fracture locations helped in identifying incorrectly located FRDs. We found that structural constraints used after careful evaluation of a priori information are critical to improve imaging of fracture electrical conductivities, locations, and orientations.
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Smart, C. C., and D. B. Ketterling. "A low-cost electrical conductivity profiler for glacier boreholes." Journal of Glaciology 43, no. 144 (1997): 365–69. http://dx.doi.org/10.3189/s0022143000003324.
Full textAbstract:
AbstractElectrical conductivity profiling allows definition of the hydrology of glacier boreholes occupied by contrasting water types. An inexpensive, robust conductivity profiling system is described that allows detailed description of borehole hydrostratigraphy with reasonable reproducibility. Field dato demonstrate the need to distinguish between bottom water in boreholes and basal water in drainage systems at the glacier bed.
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Copland, Luke, Jon Harbor, Marie Minner, and Martin Sharp. "The use of borehole inclinometry in determining basal sliding and internal deformation at Haut Glacier d’Arolla, Switzerland." Annals of Glaciology 24 (1997): 331–37. http://dx.doi.org/10.3189/s0260305500012404.
Full textAbstract:
A series of boreholes were drilled with high-pressure hot water across a section of Haut Glacier d’Arolla, Switzerland, in summer 1995. Twenty-three of the boreholes were profiled with a digital inclinometer soon aller drilling, and 14 were re-profiled up to 6 weeks later to determine changes in the longitudinal shape of boreholes with time. In addition to the main surveys, three boreholes were surveyed 14 times each to assess the accuracy and reproducibility of inclinometry measurements. These repeat surveys suggest that caution is needed in the interpretation of short-term borehole displacement measurements, and that the reoccupation of boreholes from one year to the next may be a better way to determine patterns of internal deformation and basal sliding. The annual scale may also have advantages in providing more long-term insight into glaciological processes than short term (single season) measurements.
46
Copland, Luke, Jon Harbor, Marie Minner, and Martin Sharp. "The use of borehole inclinometry in determining basal sliding and internal deformation at Haut Glacier d’Arolla, Switzerland." Annals of Glaciology 24 (1997): 331–37. http://dx.doi.org/10.1017/s0260305500012404.
Full textAbstract:
A series of boreholes were drilled with high-pressure hot water across a section of Haut Glacier d’Arolla, Switzerland, in summer 1995. Twenty-three of the boreholes were profiled with a digital inclinometer soon aller drilling, and 14 were re-profiled up to 6 weeks later to determine changes in the longitudinal shape of boreholes with time. In addition to the main surveys, three boreholes were surveyed 14 times each to assess the accuracy and reproducibility of inclinometry measurements. These repeat surveys suggest that caution is needed in the interpretation of short-term borehole displacement measurements, and that the reoccupation of boreholes from one year to the next may be a better way to determine patterns of internal deformation and basal sliding. The annual scale may also have advantages in providing more long-term insight into glaciological processes than short term (single season) measurements.
47
Qin, Wei, and Jialin Xu. "Dynamic Secondary Borehole-Sealing Method for Gas Drainage Boreholes along the Coal Seam." Geofluids 2018 (July 17, 2018): 1–11. http://dx.doi.org/10.1155/2018/1723019.
Full textAbstract:
Under the influence of advanced abutment pressure, the tightness of a borehole is destroyed, so secondary borehole sealing is needed; however, the opportune time for a secondary borehole sealing is unclear. In addition, current borehole-sealing devices do not have a secondary borehole-sealing functionality. In this paper, an opportunity election model of secondary borehole sealing was established, and a dynamic secondary borehole-sealing device was developed. In working face 3908 of the Kaiyuan Coal Mine, an in situ dynamic secondary borehole-sealing test was conducted. The test results show that the tightness of the boreholes sealed with high-water-expansion slurry is obviously better than that of the boreholes sealed with cement mortar and polyurethane. When a borehole is destroyed by the peak of the advanced abutment pressure, the secondary borehole-sealing measures can significantly improve borehole suction pressure, gas concentration, and gas drainage amount in the advanced abutment pressure loading stage.
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Chang, Chenxu, Jun Dong, and Wenqiang Ju. "Effects of Borehole Arrangement on Methane Migration and Implications for High Efficiency Extraction in Intact and Tectonic Combined Coal Seams." Geofluids 2022 (September 17, 2022): 1–13. http://dx.doi.org/10.1155/2022/9744390.
Full textAbstract:
Gas extraction by bedding boreholes is a key means to realize safe mining of coal mine and protect the environment. The traditional bedding boreholes are usually constructed in the center of the coal seam, which may not obtain a high methane extraction rate because of the existence of tectonic coal sublayer with low permeability. In this paper, the gas migration characteristics of combined coal seams composed of tectonic and intact coal sublayers are investigated, and the efficient gas extraction method is further explored. The results indicate that only 2.676 kg/m3 of gas can be extracted under the traditional bedding borehole arrangement in 300 days. The tectonic coal sublayer with low permeability restricts the gas in the intact coal sublayers to flow to the extraction boreholes, which is the main reason for the low gas extraction rate. By arranging boreholes up and down alternately with a vertical spacing of 2.74 m, the maximum gas amount of 3.526 kg/m3 can be extracted, showing an increased rate of 31.8%. The optimal vertical spacing between adjacent boreholes (VSAB) raises with the relatively increasing thickness or decreasing permeability of the tectonic coal sublayer. The optimal VSAB has a linear relationship with the thickness ratio of the tectonic coal sublayer to the combined coal seams. The optimal VSAB can be obtained referring to the numerical relationship, and then, the extraction boreholes can be dilled to achieve efficient gas extraction of combined coal seams. In engineering, the dislocation arrangement of borehole can greatly improve the gas extraction efficiency and coal mine safety.
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Li, Yaoguo, and Douglas W. Oldenburg. "Joint inversion of surface and three‐component borehole magnetic data." GEOPHYSICS 65, no. 2 (March 2000): 540–52. http://dx.doi.org/10.1190/1.1444749.
Full textAbstract:
The inversion of magnetic data is inherently nonunique with respect to the distance between the source and observation locations. This manifests itself as an ambiguity in the source depth when surface data are inverted and as an ambiguity in the distance between the source and boreholes if borehole data are inverted. Joint inversion of surface and borehole data can help to reduce this nonuniqueness. To achieve this, we develop an algorithm for inverting data sets that have arbitrary observation locations in boreholes and above the surface. The algorithm depends upon weighting functions that counteract the geometric decay of magnetic kernels with distance from the observer. We apply these weighting functions to the inversion of three‐component magnetic data collected in boreholes and then to the joint inversion of surface and borehole data. Both synthetic and field data sets are used to illustrate the new inversion algorithm. When borehole data are inverted directly, three‐component data are far more useful in constructing good susceptibility models than are single‐component data. However, either can be used effectively in a joint inversion with surface data to produce models that are superior to those obtained by inversion of surface data alone.
50
Kulessa, Bernd, and Bryn Hubbard. "Interpretation of borehole impulse tests at Haut Glacier d’Arolla, Switzerland." Annals of Glaciology 24 (1997): 397–402. http://dx.doi.org/10.1017/s0260305500012507.
Full textAbstract:
One hundred and sixteen impulse tests were conducted in a dense borehole array at Haut Glacier d’Arolla, Switzerland, during July and August 1995. Impulse-test response pressure oscillations reveal marked variations in three parameters: relative amplitude decay, oscillation frequency and net water-level displacement. Analysis of response signals from water-filled boreholes indicates that (i) responses from individual boreholes are reproducible over some tens of minutes; (ii) responses are similar, but not identical, for slug insertion (“slug tests”) and removal (“bail tests”); (iii) signal amplitude decay varies with the depth at which the recording pressure transducer is located in a borehole; and (iv) coherent minima in all three response parameters coincide with the location of a known preferential, subglacial water-flow pathway. This correspondence suggests, first, that water-filled and non-fluctuating boreholes have established a link to the subglacial aquifer at Haut Glacier d’Arolla and, secondly, that locally transmissive basal sediments may be identified by relatively low response-signal frequencies, response-signal decays and net water-level displacements. Impulse testing water-filled boreholes therefore has the capacity to provide information relating to the local hydrogeological properties of subglacial aquifers. In 43 cases, water levels in boreholes adjacent to those being tested were recorded in order to identify possible subglacial linkages. No such connections were detected.