Journal articles on the topic 'Hydrate Saturation'
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1
Wei, Jiangong, Tingting Wu, Xiuli Feng, Jinqiang Liang, Wenjing Li, Rui Xie, and Gang Wu. "Physical Properties of Gas Hydrate-Bearing Pressure Core Sediments in the South China Sea." Geofluids 2021 (April 29, 2021): 1–10. http://dx.doi.org/10.1155/2021/6636125.
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Gas hydrates are a potential future energy resource and are widely distributed in marine sediments and permafrost areas. The physical properties and mechanical behavior of gas hydrate-bearing sediments are of great significance to seafloor stability and platform safety. In 2013, a large number of pressure cores were recovered during China’s second gas hydrate drilling expedition in the South China Sea. In this study, we determined the gas hydrate distribution, saturation, physical properties, and mechanical behavior of the gas hydrate-bearing sediments by conducting Multi-Sensor Core Logger measurements and triaxial and permeability tests. Disseminated gas hydrates, gas hydrate veins, and gas hydrate slabs were observed in the sediments. The gas hydrate distribution and saturation are spatially heterogeneous, with gas hydrate saturations of 0%–55.3%. The peak deviatoric stress of the gas hydrate-bearing sediments is 0.14–1.62 MPa under a 0.15–2.3 MPa effective confining stress. The permeability is 0.006– 0.095 × 10 − 3 μ m 2 , and it decreases with increasing gas hydrate saturation and burial depth.
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Chen, Yuan, Shiguo Wu, Ting Sun, and Shu Jia. "Study of the Appropriate Well Types and Parameters for the Safe and Efficient Production of Marine Gas Hydrates in Unconsolidated Reservoirs." Energies 15, no. 13 (June 30, 2022): 4796. http://dx.doi.org/10.3390/en15134796.
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The majority of marine hydrates are buried in unconsolidated or poorly consolidated marine sediments with limited cementation and strength. As a result, hydrate decomposition during production may cause the significant subsidence of the formation, necessitating a halt in production. The numerical model of unconsolidated hydrate formation, based on geomechanics, was established in order to elucidate the depressurization production process. The sensitive factors of unconsolidated hydrate production were determined by analyzing the influence of formation parameters and production parameters on gas production. Then, a safety formation subsidence was proposed in this paper, and the appropriate well type and parameters for the safe and efficient production of hydrates in unconsolidated formations of various saturations were determined. The sensitivity of gas production to the formation parameters was in the order of formation porosity, hydrate saturation, and buried depth, while the effects of the production parameters were BHP (bottom hole pressure), horizontal length, and the heat injection, in descending order. For hydrate reservoirs in the South China Sea, when the hydrate saturation is 20%, a horizontal well is necessary and the appropriate horizontal length should be less than 80 m. However, when hydrate saturation is more than 30%, a vertical well should be selected, and the appropriate bottom hole pressure should be no less than 3800 kPa and 4800 kPa for 30% and 40% saturation, respectively. Based on the simulation results, hydrate saturation was the key factor by which to select an appropriate production technique in advance and adjust the production parameters. The study has elucidated the depressurization production of marine unconsolidated hydrate formations at depth, which has numerous implications for field production.
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Du, Bing-rui, Da-wei Bai, Peng-hui Zhang, Peng Guo, and Qiang Zhang. "Physical Experiment Research on Dielectric Properties of Hydrate-bearing Sediment in Sandstone Reservoir." E3S Web of Conferences 118 (2019): 03046. http://dx.doi.org/10.1051/e3sconf/201911803046.
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Dielectric constants can be used to detect hydrates in permafrost regions. Therefore, this study investigated the relationships between the dielectric constant characteristics of sandstone reservoir hydrate and the hydrate saturation degree through physical simulation experiments, as well as the granularity of the surrounding rock. Methane and tetrahydrofuran (THF) hydrates with quartz sands were prepared, and their dielectric constants were analyzed. With different granularities of quartz sands, the dielectric constants of two different methane hydrate sediments decreased with increasing saturation degrees. At a given saturation degree, the dielectric constant of methane hydrate sediments with small granularity was larger than that with medium granularity, a result attributed to the unreacted water in the larger pores of the latter. In addition, the dielectric constant of methane hydrate sediments was larger than that of THF hydrates, which was also attributed to gas-phase factors and the presence of unreacted water. At a given granularity and saturation, the dielectric constants of both the THF and methane hydrates decreased with increasing saturation degrees. We conclude that at low temperature and under normal pressure, THF hydrates cannot be used as a substitute for methane hydrates in laboratory experiments investigating geophysical phenomena.
4
Guo, Zhiqi, Xiaoyu Lv, Cai Liu, Haifeng Chen, and Zhiguang Cai. "Characterizing Gas Hydrate–Bearing Marine Sediments Using Elastic Properties—Part 1: Rock Physical Modeling and Inversion from Well Logs." Journal of Marine Science and Engineering 10, no. 10 (September 27, 2022): 1379. http://dx.doi.org/10.3390/jmse10101379.
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Gas hydrates are considered a potential energy source for the future. Rock physics modeling provides insights into the elastic response of sediments containing gas hydrates, which is essential for identifying gas hydrates using well-log data and seismic attributes. This paper establishes a rock physics model (RPM) by employing effective medium theories to quantify the elastic properties of sediments containing gas hydrates. Specifically, the proposed RPM introduces critical gas hydrate saturation for various modeling schemes. Such a key factor considers the impact of gas hydrates on sediment stiffnesses during the dynamic process of the gas hydrate accumulating as pore fillings and part of the solid components. Theoretical modeling illustrates that elastic characteristics of the sediments exhibit distinct variation trends determined by critical gas hydrate saturation. Numerical tests of the model based on the well-log data confirm that the proposed technique can be employed to rationally predict gas hydrate saturation using the elastic properties. The compressional wave velocity model is also developed to estimate the gas hydrate saturation, which gives reliable fit results to core measurement data. The proposed methods could improve our understanding of the elastic behaviors of gas hydrates, providing a practical approach to estimating their concentrations.
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Sahoo, Sourav K., Laurence J. North, Hector Marín-Moreno, Tim A. Minshull, and Angus I. Best. "Laboratory observations of frequency-dependent ultrasonic P-wave velocity and attenuation during methane hydrate formation in Berea sandstone." Geophysical Journal International 219, no. 1 (July 17, 2019): 713–23. http://dx.doi.org/10.1093/gji/ggz311.
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SUMMARY Knowledge of the effect of methane hydrate saturation and morphology on elastic wave attenuation could help reduce ambiguity in seafloor hydrate content estimates. These are needed for seafloor resource and geohazard assessment, as well as to improve predictions of greenhouse gas fluxes into the water column. At low hydrate saturations, measuring attenuation can be particularly useful as the seismic velocity of hydrate-bearing sediments is relatively insensitive to hydrate content. Here, we present laboratory ultrasonic (448–782 kHz) measurements of P-wave velocity and attenuation for successive cycles of methane hydrate formation (maximum hydrate saturation of 26 per cent) in Berea sandstone. We observed systematic and repeatable changes in the velocity and attenuation frequency spectra with hydrate saturation. Attenuation generally increases with hydrate saturation, and with measurement frequency at hydrate saturations below 6 per cent. For hydrate saturations greater than 6 per cent, attenuation decreases with frequency. The results support earlier experimental observations of frequency-dependent attenuation peaks at specific hydrate saturations. We used an effective medium rock-physics model which considers attenuation from gas bubble resonance, inertial fluid flow and squirt flow from both fluid inclusions in hydrate and different aspect ratio pores created during hydrate formation. Using this model, we linked the measured attenuation spectral changes to a decrease in coexisting methane gas bubble radius, and creation of different aspect ratio pores during hydrate formation.
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Sun, Jian Ye, Yu Guang Ye, Chang Ling Liu, and Jian Zhang. "Experimental Study on Gas Production from Methane Hydrate Bearing Sand by Depressurization." Applied Mechanics and Materials 310 (February 2013): 28–32. http://dx.doi.org/10.4028/www.scientific.net/amm.310.28.
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The simulate experiments of gas production from methane hydrates reservoirs was proceeded with an experimental apparatus. Especially, TDR technique was applied to represent the change of hydrate saturation in real time during gas hydrate formation and dissociation. In this paper, we discussed and explained material transformation during hydrate formation and dissociation. The hydrates form and grow on the top of the sediments where the sediments and gas connect firstly. During hydrates dissociation by depressurization, the temperatures and hydrate saturation presented variously in different locations of sediments, which shows that hydrates dissociate earlier on the surface and outer layer of the sediments than those of in inner. The regulation of hydrates dissociation is consistent with the law of decomposition kinetics. Furthermore, we investigated the depressurizing range influence on hydrate dissociation process.
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Bu, Qingtao, Tongju Xing, Gaowei Hu, Changling Liu, Chengfeng Li, Jinhuan Zhao, Zihao Wang, Wengao Zhao, and Jiale Kang. "Methane Flux Effect on Hydrate Formation and Its Acoustic Responses in Natural Sands." Geofluids 2022 (May 30, 2022): 1–12. http://dx.doi.org/10.1155/2022/7746386.
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The acoustic properties of hydrate deposits are important parameters for hydrate geophysical exploration, and the gas leakage model plays a very important role in hydrate accumulation systems. In order to reflect the gas supply environment during hydrate formation, a high-pressure device with a simulated leakage system was designed to achieve different methane flux supplies. The effects of different methane fluxes on the hydrate formation rate and the maximum hydrate saturation were obtained. The results in this study indicate that similar hydrate formation rates occur in systems with different methane fluxes. However, when the methane flux is large, it takes longer to reach the maximum hydrate saturation, and the larger the methane flux, the larger the hydrate saturation formed. In each methane flux system, the elastic velocity increased slowly with increasing hydrate saturation at the beginning of hydrate formation, but velocity increased quickly when the hydrate saturation reached 50–60%. In order to take into account the effect of the gas, the calculated values of the elastic velocity model were compared with the experimental data, which indicated that the BGTL theory and the EMT model are more adaptable and can be used to deduce hydrate morphology. In the large methane flux system, the hydrate mainly forms at grain contacts when the hydrate saturation is 10–60%. As the hydrate saturation reaches 60–70%, hydrate forms first in the pore fluid, and then the hydrates contact sediment particles.
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Jarrar, Zaher, Riyadh Al-Raoush, Khalid Alshibli, and Jongwon Jung. "Dynamic 3D imaging of gas hydrate kinetics using synchrotron computed tomography." E3S Web of Conferences 205 (2020): 11004. http://dx.doi.org/10.1051/e3sconf/202020511004.
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The availability of natural gas hydrates and the continuing increase in energy demand, motivated researchers to consider gas hydrates as a future source of energy. Fundamental understanding of hydrate dissociation kinetics is essential to improve techniques of gas production from natural hydrates reservoirs. During hydrate dissociation, bonds between water (host molecules) and gas (guest molecules) break and free gas is released. This paper investigates the evolution of hydrate surface area, pore habit, and tortuosity using in-situ imaging of Xenon (Xe) hydrate formation and dissociation in porous media with dynamic three-dimensional synchrotron microcomputed tomography (SMT). Xe hydrate was formed inside a high- pressure, low-temperature cell and then dissociated by thermal stimulation. During formation and dissociation, full 3D SMT scans were acquired continuously and reconstructed into 3D volume images. Each scan took only 45 seconds to complete, and a total of 60 scans were acquired. Hydrate volume and surface area evolution were directly measured from the SMT scans. At low hydrate saturation, the predominant pore habit was surface coating, while the predominant pore habit at high hydrate saturation was pore filling. A second-degree polynomial can be used to predict variation of tortuosity with hydrate saturation with an R2 value of 0.997.
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Zhao, Jinhuan, Changling Liu, Chengfeng Li, Yongchao Zhang, Qingtao Bu, Nengyou Wu, Yang Liu, and Qiang Chen. "Pore-Scale Investigation of the Electrical Property and Saturation Exponent of Archie’s Law in Hydrate-Bearing Sediments." Journal of Marine Science and Engineering 10, no. 1 (January 14, 2022): 111. http://dx.doi.org/10.3390/jmse10010111.
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Characterizing the electrical property of hydrate-bearing sediments is essential for hydrate reservoir identification and saturation evaluation. As the major contributor to electrical conductivity, pore water is a key factor in characterizing the electrical properties of hydrate-bearing sediments. The objective of this study is to clarify the effect of hydrates on pore water and the relationship between pore water characteristics and the saturation exponent of Archie’s law in hydrate-bearing sediments. A combination of X-ray computed tomography and resistivity measurement technology is used to derive the three-dimensional spatial structure and resistivity of hydrate-bearing sediments simultaneously, which is helpful to characterize pore water and investigate the saturation exponent of Archie’s law at the micro-scale. The results show that the resistivity of hydrate-bearing sediments is controlled by changes in pore water distribution and connectivity caused by hydrate formation. With the increase of hydrate saturation, pore water connectivity decreases, but the average coordination number and tortuosity increase due to much smaller and more tortuous throats of pore water divided by hydrate particles. It is also found that the saturation exponent of Archie’s law is controlled by the distribution and connectivity of pore water. As the parameters of connected pore water (e.g., porosity, water saturation) decrease, the saturation exponent decreases. At a low hydrate-saturation stage, the saturation exponent of Archie’s law changes obviously due to the complicated pore structure of hydrate-bearing sediments. A new logarithmic relationship between the saturation exponent of Archie’s law and the tortuosity of pore water is proposed which helps to calculate field hydrate saturation using resistivity logging data.
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Li, Xingbo, Yu Liu, Hanquan Zhang, Bo Xiao, Xin Lv, Haiyuan Yao, Weixin Pang, et al. "Non-Embedded Ultrasonic Detection for Pressure Cores of Natural Methane Hydrate-Bearing Sediments." Energies 12, no. 10 (May 24, 2019): 1997. http://dx.doi.org/10.3390/en12101997.
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An apparatus for the analysis of pressure cores containing gas hydrates at in situ pressures was designed, and a series of experiments to determine the compressional wave response of hydrate-bearing sands were performed systematically in the laboratory. Considering the difficulties encountered in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples, the laboratory approach enabled closer study than the marine environment due to sample recovery problems. The apparatus was designed to achieve in situ hydrate formation in bearing sediments and synchronous ultrasonic detection. The P-wave velocity measurements enabled quick and successive ultrasonic analysis of pressure cores. The factors influencing P-wave velocity (Vp), including hydrate saturation and formation methodology, were investigated. By controlling the initial water saturation and gas pressure, we conducted separate experiments for different hydrate saturation values ranging from 2% to 60%. The measured P-wave velocity varied from less than 1700 m/s to more than 3100 m/s in this saturation range. The hydrate saturation can be successfully predicted by a linear fitting of the attenuation (Q−1) to the hydrate saturation. This approach provided a new method for acoustic measurement of the hydrate saturation when the arrival time of the first wave cannot be directly distinguished. Our results demonstrated that the specially designed non-embedded ultrasonic detection apparatus could determine the hydrate saturation and occurrence patterns in pressure cores, which could assist further hydrate resource exploration and detailed core analyses.
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Benmesbah, Fatima Doria, Livio Ruffine, Pascal Clain, Véronique Osswald, Olivia Fandino, Laurence Fournaison, and Anthony Delahaye. "Methane Hydrate Formation and Dissociation in Sand Media: Effect of Water Saturation, Gas Flowrate and Particle Size." Energies 13, no. 19 (October 6, 2020): 5200. http://dx.doi.org/10.3390/en13195200.
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Assessing the influence of key parameters governing the formation of hydrates and determining the capacity of the latter to store gaseous molecules is needed to improve our understanding of the role of natural gas hydrates in the oceanic methane cycle. Such knowledge will also support the development of new industrial processes and technologies such as those related to thermal energy storage. In this study, high-pressure laboratory methane hydrate formation and dissociation experiments were carried out in a sandy matrix at a temperature around 276.65 K. Methane was continuously injected at constant flowrate to allow hydrate formation over the course of the injection step. The influence of water saturation, methane injection flowrate and particle size on hydrate formation kinetics and methane storage capacity were investigated. Six water saturations (10.8%, 21.6%, 33%, 43.9%, 55% and 66.3%), three gas flowrates (29, 58 and 78 mLn·min−1) and three classes of particle size (80–140, 315–450 and 80–450 µm) were tested, and the resulting data were tabulated. Overall, the measured induction time obtained at 53–57% water saturation has an average value of 58 ± 14 min minutes with clear discrepancies that express the stochastic nature of hydrate nucleation, and/or results from the heterogeneity in the porosity and permeability fields of the sandy core due to heterogeneous particles. Besides, the results emphasize a clear link between the gas injection flowrate and the induction time whatever the particle size and water saturation. An increase in the gas flowrate from 29 to 78 mLn·min−1 is accompanied by a decrease in the induction time up to ~100 min (i.e., ~77% decrease). However, such clear behaviour is less conspicuous when varying either the particle size or the water saturation. Likewise, the volume of hydrate-bound methane increases with increasing water saturation. This study showed that water is not totally converted into hydrates and most of the calculated conversion ratios are around 74–84%, with the lowest value of 49.5% conversion at 54% of water saturation and the highest values of 97.8% for the lowest water saturation (10.8%). Comparison with similar experiments in the literature is also carried out herein.
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Almenningen, Stian, Per Fotland, Martin A. Fernø, and Geir Ersland. "An Experimental Investigation of Gas-Production Rates During Depressurization of Sedimentary Methane Hydrates." SPE Journal 24, no. 02 (January 9, 2019): 522–30. http://dx.doi.org/10.2118/190811-pa.
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Summary Sedimentary methane hydrates contain a vast amount of untapped natural gas that can be produced through pressure depletion. Several field pilots have proved the concept with days to weeks of operation, but the longer-term response remains uncertain. This paper investigates the parameters affecting the rate of gas recovery from methane-hydrate-bearing sediments. The recovery of methane gas from hydrate dissociation through pressure depletion was studied at different initial hydrate saturations and different constant production pressures in cylindrical sandstone cores. Core-scale dissociation patterns were mapped with magnetic resonance imaging (MRI), and pore-scale dissociation events were visualized in a high-pressure micromodel. Key findings from the gas-production-rate analysis are that the maximum rate of recovery is only to a small extent affected by the magnitude of the pressure reduction below the dissociation pressure, and that the hydrate saturation directly affects the rate of recovery, where intermediate hydrate saturations (0.30 to 0.50) give the highest initial recovery rate. These results are of interest to anyone who evaluates the production performance of sedimentary hydrate accumulations and demonstrate how important accurate saturation estimates are to prediction of both the initial rate of gas recovery and the ultimate-recovery efficiency.
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Sun, Zhong Ming, Jian Zhang, Chang Ling Liu, Shi Jun Zhao, and Yu Guang Ye. "Experimental Study on the In Situ Mechanical Properties of Methane Hydrate-Bearing Sediments." Applied Mechanics and Materials 275-277 (January 2013): 326–31. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.326.
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TDR was introduced to solve the problem of how to measure hydrate saturation accurately. Then a series of un-drained triaxial tests were carried out on methane hydrate-bearing sediments under various conditions with effective confining pressures at 1, 2 and 4 MPa, average hydrate saturations at 15.71, 35.7 and 56.49% and strain rate at 0.8%/min. The results indicate that the shear strength increases with the increases of effective confining pressure and hydrate saturation, but the maximum failure time decreases with the increasing effective confining pressures. According to Mohr-Coulomb failure criterion, the shear strength of methane hydrate-bearing sediments was analyzed. It can be found that the internal friction angles are not sensitive to hydrate saturation, but the cohesion shows a high hydrate saturation dependency.
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Lu, Shaoming, and George A. McMechan. "Estimation of gas hydrate and free gas saturation, concentration, and distribution from seismic data." GEOPHYSICS 67, no. 2 (March 2002): 582–93. http://dx.doi.org/10.1190/1.1468619.
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Gas hydrates contain a major untapped source of energy and are of potential economic importance. The theoretical models to estimate gas hydrate saturation from seismic data predict significantly different acoustic/elastic properties of sediments containing gas hydrate; we do not know which to use. Thus, we develop a new approach based on empirical relations. The water‐filled porosity is calibrated (using well‐log data) to acoustic impedance twice: one calibration where gas hydrate is present and the other where free gas is present. The water‐filled porosity is used in a combination of Archie equations (with corresponding parameters for either gas hydrate or free gas) to estimate gas hydrate or free gas saturations. The method is applied to single‐channel seismic data and well logs from Ocean Drilling Program leg 164 from the Blake Ridge area off the east coast of North America. The gas hydrate above the bottom simulating reflector (BSR) is estimated to occupy ∼3–8% of the pore space (∼2–6% by volume). Free gas is interpreted to be present in three main layers beneath the BSR, with average gas saturations of 11–14%, 7–11%, and 1–5% of the pore space (6–8%, 4–6%, and 1–3% by volume), respectively. The estimated saturations of gas hydrate are very similar to those estimated from vertical seismic profile data and generally agree with those from independent, indirect estimates obtained from resistivity and chloride measurements. The estimated free gas saturations agree with measurements from a pressure core sampler. These results suggest that locally derived empirical relations between porosity and acoustic impedance can provide cost‐effective estimates of the saturation, concentration, and distribution of gas hydrate and free gas away from control wells.
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Qian, Jin, Xiujuan Wang, Timothy S. Collett, Dongdong Dong, Yiqun Guo, Pibo Su, and Jinqiang Liang. "Gas hydrate accumulation and saturations estimated from effective medium theory in the eastern Pearl River Mouth Basin, South China Sea." Interpretation 5, no. 3 (August 31, 2017): SM33—SM48. http://dx.doi.org/10.1190/int-2016-0217.1.
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Pore- and fracture-filling gas hydrates were identified from the core samples at several sites during the second Guangzhou Marine Geological Survey (GMGS2) expedition. Well logs indicated that gas hydrate occurred in three distinct layers at site GMGS2-08. The gas hydrate saturations calculated from well-log data and the seismic responses for the three gas hydrate-bearing layers, especially within the middle carbonate layer, were poorly known. We estimated gas hydrate saturations using isotropic and anisotropic models based on the mineral composition of the sediments and the effective medium theory. In the upper and lower gas hydrate-bearing layers, saturations estimated from anisotropic models are close to those estimated from pressures cores and chlorinity data. The average saturation using an anisotropic model in the upper (fracture-dominated) hydrate layer is approximately 10% with a maximum value of 25%. In the lower (fracture-dominated) layer, the horizontal and vertical gas hydrate-filled fractures and visible gas hydrate were formed with a maximum saturation of approximately 85%. For the middle layer, well logs show high P-wave velocity, density, high resistivity as well as low gamma ray, porosity, and drilling rate, together indicating a carbonate layer containing gas hydrate. The hydrate saturations calculated from isotropic models assuming hydrate formed at grain contacts are less than 20%, which fit well with two values calculated from chlorinity data for this layer. The upper gas hydrate layer shows no clear seismic response and probably consisted of small fractures filled with gas hydrate. The middle carbonate and lower fracture-filled gas hydrate-bearing layers show pull-up reflections, with the carbonate layer exhibiting relatively higher amplitudes. Pore-filling gas hydrate was also identified just above the depth of the bottom-simulating-reflector (BSR) from the GMGS2-05 drill site. Below the BSR, the push-down reflections, polarity reversal, and enhanced reflections indicate the occurrence of free gas in the study area.
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Li, Dongliang, Dong Wang, and Deqing Liang. "P-wave of hydrate-bearing sand under temperature cycling." GEOPHYSICS 76, no. 1 (January 2011): E1—E7. http://dx.doi.org/10.1190/1.3515263.
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P-wave velocity was used to study the formation of gas hydrates that were formed from methane, [Formula: see text], and propane in the pores of sand particles under temperature cycling. During the temperature-cycling tests, additional hydrate or ice formation can be demonstrated by investigating the velocities and amplitude of the P-wave. The experiments indicated that temperature cycling can accelerate hydrate accumulation in the pore space of sediments. Although most of the water in the pore space of sand can transform into gas hydrate after several temperature cycles, the formation of propane hydrate was slower than that of methane hydrate or [Formula: see text] hydrate. To estimate the hydrate saturation, an effective-medium theory was used. The results corroborated the validity of the contact model that the hydrate acted as a mineral grain to support the sediment frame. According to the calculation results, the methane-hydrate saturation can be up to 0.85 after three temperature cycles. The evaluation results accord with those of some natural hydrates in sand layers.
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De La Fuente, Maria, Jean Vaunat, and Héctor Marín-Moreno. "Modelling Methane Hydrate Saturation in Pores: Capillary Inhibition Effects." Energies 14, no. 18 (September 7, 2021): 5627. http://dx.doi.org/10.3390/en14185627.
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Experimental and field observations evidence the effects of capillarity in narrow pores on inhibiting the thermodynamic stability of gas hydrates and controlling their saturation. Thus, precise estimates of the gas hydrate global inventory require models that accurately describe gas hydrate stability in sediments. Here, an equilibrium model for hydrate formation in sediments that accounts for capillary inhibition effects is developed and validated against experimental data. Analogous to water freezing in pores, the model assumes that hydrate formation is controlled by the sediment pore size distribution and the balance of capillary forces at the hydrate–liquid interface. To build the formulation, we first derive the Clausius–Clapeyron equation for the thermodynamic equilibrium of methane and water chemical potentials. Then, this equation is combined with the van Genuchten’s capillary pressure to relate the thermodynamic properties of the system to the sediment pore size distribution and hydrate saturation. The model examines the influence of the sediment pore size distribution on hydrate saturation through the simulation of hydrate formation in sand, silt, and clays, under equilibrium conditions and without mass transfer limitations. The results show that at pressure–temperature conditions typically found in the seabed, capillary effects in very fine-grained clays can limit the maximum hydrate saturation below 20% of the host sediment porosity.
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Wang, Lei, Jin Yang, Lilin Li, Ting Sun, and Dongsheng Xu. "Study on the Mechanical Properties of Natural Gas Hydrate Reservoirs with Multicomponent under Different Engineering Conditions." Energies 15, no. 23 (November 27, 2022): 8958. http://dx.doi.org/10.3390/en15238958.
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For wellbore stability issues induced by drilling operations in natural gas hydrate-containing reservoirs, wellbore stability research will focus on the mechanical properties of hydrate reservoirs. According to the content of the research, the response relationship between the hydrate core and the base physical property changes under different engineering parameters is established, and the law of hydrate mechanical property changes with temperature and pressure is studied for various physical properties. According to theoretical research and experimental data, it has been determined that: hydrate core-resolved gas and transverse and longitudinal wave velocity have a positive correlation with saturation and pressure and a negative correlation with temperature; a negative correlation exists between resistivity and saturation. The hydrate core stiffness strength correlates positively with saturation and adversely with temperature. Under the identical strain conditions, when saturation, pore pressure, and temperature increase, the stress of the hydrate grows rapidly; there is a distinct inflection point, and the hydrate does not form above a particular temperature. To prevent the decomposition of hydrates and minimize disasters such as well wall instability and reservoir collapse, it is possible to reduce reservoir in situ temperature and pressure fluctuations in accordance with operational requirements.
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Gauteplass, Jarand, Stian Almenningen, Tanja Barth, and Geir Ersland. "Hydrate Plugging and Flow Remediation during CO2 Injection in Sediments." Energies 13, no. 17 (September 1, 2020): 4511. http://dx.doi.org/10.3390/en13174511.
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Successful geological sequestration of carbon depends strongly on reservoir seal integrity and storage capacity, including CO2 injection efficiency. Formation of solid hydrates in the near-wellbore area during CO2 injection can cause permeability impairment and, eventually, injectivity loss. In this study, flow remediation in hydrate-plugged sandstone was assessed as function of hydrate morphology and saturation. CO2 and CH4 hydrates formed consistently at elevated pressures and low temperatures, reflecting gas-invaded zones containing residual brine near the injection well. Flow remediation by methanol injection benefited from miscibility with water; the methanol solution contacted and dissociated CO2 hydrates via liquid water channels. Injection of N2 gas did not result in flow remediation of non-porous CO2 and CH4 hydrates, likely due to insufficient gas permeability. In contrast, N2 as a thermodynamic inhibitor dissociated porous CH4 hydrates at lower hydrate saturations (<0.48 frac.). Core-scale thermal stimulation proved to be the most efficient remediation method for near-zero permeability conditions. However, once thermal stimulation ended and pure CO2 injection recommenced at hydrate-forming conditions, secondary hydrate formation occurred aggressively due to the memory effect. Field-specific remediation methods must be included in the well design to avoid key operational challenges during carbon injection and storage.
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Zaripova, Yulia, Vladimir Yarkovoi, Mikhail Varfolomeev, Rail Kadyrov, and Andrey Stoporev. "Influence of Water Saturation, Grain Size of Quartz Sand and Hydrate-Former on the Gas Hydrate Formation." Energies 14, no. 5 (February 25, 2021): 1272. http://dx.doi.org/10.3390/en14051272.
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The development of technologies for the accelerated formation or decomposition of gas hydrates is an urgent topic. This will make it possible to utilize a gas, including associated petroleum one, into a hydrate state for its further use or to produce natural gas from hydrate-saturated sediments. In this work, the effect of water content in wide range (0.7–50 mass%) and the size of quartz sand particles (porous medium; <50 μm, 125–160 μm and unsifted sand) on the formation of methane and methane-propane hydrates at close conditions (subcooling value) has been studied. High-pressure differential scanning calorimetry and X-ray computed tomography techniques were employed to analyze the hydrate formation process and pore sizes, respectively. The exponential growth of water to hydrate conversion with a decrease in the water content due to the rise of water–gas surface available for hydrate formation was revealed. Sieving the quartz sand resulted in a significant increase in water to hydrate conversion (59% for original sand compared to more than 90% for sieved sand). It was supposed that water suction due to the capillary forces influences both methane and methane-propane hydrates formation as well with latent hydrate forming up to 60% either without a detectable heat flow or during the ice melting. This emphasizes the importance of being developed for water–gas (ice–gas) interface to effectively transform water into the hydrate state. In any case, the ice melting (presence of thawing water) may allow a higher conversion degree. Varying the water content and the sand grain size allows to control the degree of water to hydrate conversion and subcooling achieved before the hydrate formation. Taking into account experimental error, the equilibrium conditions of hydrates formation do not change in all studied cases. The data obtained can be useful in developing a method for obtaining hydrates under static conditions.
21
Liu, Lele, Nengyou Wu, Changling Liu, Qingguo Meng, Haitao Tian, Yizhao Wan, and Jianye Sun. "Maximum Sizes of Fluid-Occupied Pores within Hydrate-Bearing Porous Media Composed of Different Host Particles." Geofluids 2020 (July 15, 2020): 1–14. http://dx.doi.org/10.1155/2020/8880286.
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Hydraulic properties of hydrate-bearing sediments are largely affected by the maximum size of pores occupied by fluids. However, effects of host particle properties on the maximum size of fluid-occupied pores within hydrate-bearing sediments remain elusive, and differences in the maximum equivalent, incircle, and hydraulic diameters of fluid-occupied pores evolving with hydrate saturation have not been well understood. In this study, numerical simulations of grain-coating and pore-filling hydrate nucleation and growth within different artificial porous media are performed to quantify the maximum equivalent, incircle, and hydraulic diameters of fluid-occupied pores during hydrate formation, and how maximum diameters of fluid-occupied pores change with hydrate saturation is analyzed. Then, theoretical models of geometry factors for incircle and hydraulic diameters are proposed based on fractal theory, and variations of fluid-occupied pore shapes during hydrate formation are discussed. Results show that host particle properties have obvious effects on the intrinsic maximum diameters of fluid-occupied pores and introduce discrepancies in evolutions of the maximum pore diameters during hydrate formation. Pore-filling hydrates reduce the maximum incircle and hydraulic diameters of fluid-occupied pores much more significantly than grain-coating hydrates; however, hydrate pore habits have minor effects on the maximum equivalent diameter reduction. Shapes of fluid-occupied pores change little due to the presence of grain-coating hydrates, but pore-filling hydrates lead to much fibrous shapes of fluid-occupied pores.
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Yuan, Yilong, Tianfu Xu, Xin Xin, and Yingli Xia. "Multiphase Flow Behavior of Layered Methane Hydrate Reservoir Induced by Gas Production." Geofluids 2017 (2017): 1–15. http://dx.doi.org/10.1155/2017/7851031.
Full textAbstract:
Gas hydrates are expected to be a potential energy resource with extensive distribution in the permafrost and in deep ocean sediments. The marine gas hydrate drilling explorations at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate deposits. Gas hydrate reservoirs are composed of alternating beds of sand and clay, with various conditions of permeability, porosity, and hydrate saturation. This study looks into the multiphase flow behaviors of layered methane hydrate reservoirs induced by gas production. Firstly, a history matching model by incorporating the available geological data at the test site of the Eastern Nankai Trough, which considers the layered heterogeneous structure of hydrate saturation, permeability, and porosity simultaneously, was constructed to investigate the production characteristics from layered hydrate reservoirs. Based on the validated model, the effects of the placement of production interval on production performance were investigated. The modeling results indicate that the dissociation zone is strongly affected by the vertical reservoir’s heterogeneous structure and shows a unique dissociation front. The beneficial production interval scheme should consider the reservoir conditions with high permeability and high hydrate saturation. Consequently, the identification of the favorable hydrate deposits is significantly important to realize commercial production in the future.
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Jaiswal, P. "Hydrate quantification: Integrating full-waveform inversion, seismic attributes, and rock physics." Interpretation 4, no. 1 (February 1, 2016): SA55—SA71. http://dx.doi.org/10.1190/int-2015-0021.1.
Full textAbstract:
Hydrate quantification from seismic data is a two-pronged challenge. The first is creating a velocity field with high enough resolution and accuracy such that it is a meaningful representation of hydrate variability in the host sediments. The second is constructing a rock-physics model that accounts for the appropriate growth of the hydrate and allows for the interpretation of the velocity field in terms of hydrate saturation. In this paper, both challenges are addressed in a quantification workflow that uses 2D seismic and colocated well logs. The study area is situated in the Krishna-Godavari Basin, offshore eastern Indian coast, where hydrate was discovered in the National Gas Hydrate Program Expedition 01 (NGHP-01). The workflow hinges on a rock-physics model that expresses total hydrate saturation in terms of primary (matrix) and secondary (fractures, faults, voids, etc.) porosities and their respective primary and secondary saturations and incorporates hydrate-filled secondary porosity into the rock as an additional grain type using the Hashin-Shtrikman bounds. The model is first applied to a set of well logs at a colocated site, NGHP-01-10, following which the application is extended into the seismic domain by (1) the incoherency attribute as a proxy for secondary porosity and (2) a full-waveform inversion-based P-wave velocity ([Formula: see text]) model as a proxy for primary saturation. The remaining — the primary porosity and secondary saturation — are assumed to remain the same across the seismic profile as at the site NGHP-01-10. The resulting, seismically estimated, hydrate saturation compares well with saturations from core depressurization at colocated sites NGHP-01-10 and NGHP-01-13. The quantification workflow presented here is potentially adaptable to other geographical areas with the caveat that empirical relations between porosity, saturation, and seismic attributes may have to be locally established.
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Li, Nan, Ziyang Fan, Haoran Ma, Shuai Jia, Jingyu Kan, Changyu Sun, and Shun Liu. "Permeability of Hydrate-Bearing Sediment Formed from CO2-N2 Mixture." Journal of Marine Science and Engineering 11, no. 2 (February 8, 2023): 376. http://dx.doi.org/10.3390/jmse11020376.
Full textAbstract:
CO2-N2-mixture injection can be used for the exploitation and reformation of natural gas hydrate reservoirs. The permeability evolution of sediments in the presence of CO2-N2 hydrate is very important. In current permeability tests, hydrate-bearing sediment formed from CO2-N2 gas mixture is rarely involved. In this work, hydrate-bearing sediment was formed from CO2-N2 mixtures, and a constant flow method was employed to measure the permeability of the hydrate-bearing sediments. The effects of CO2 mole fraction and hydrate saturation on the permeability were investigated. The results show that gas composition is the key factor affecting hydrate formation. Hydrate saturation increases with increasing CO2 mole fraction in the gas mixture. The presence of hydrate formed from a CO2-N2 mixture leads to a sharp permeability reduction. The higher the fraction of CO2 in the injected gas mixture, the lower the sediment’s permeability. Our measured permeability data were also compared with and fitted to prediction models. The pore-filling model underestimates the permeability of hydrate-bearing sediments formed from a CO2-N2 gas mixture. The fitted hydrate saturation index in the Masuda model is 15.35, slightly higher than the general values, which means that the formed hydrates tend to occupy the pore center, and even block the pore throat.
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Li, Ling Dong, Yuan Fang Cheng, and Xiao Jie Sun. "Experimental Study on Dynamic Elastic Properties of Gas Hydrate Bearing Sediments." Advanced Materials Research 446-449 (January 2012): 1396–99. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.1396.
Full textAbstract:
As a kind of emerging energy with massive reserves, natural gas hydrates are becoming the hot spot of global research. The elastic properties of gas hydrate bearing sediments (HBS) are the fundamental parameters for gas hydrates exploration and resource evaluations. As the original coring in HBS is difficult and expensive, experimental method is important to study the problem. An acoustic wave in-situ measuring system for HBS was developed. Using the in-situ method, hydrate bearing rock samples of different hydrate saturation were synthesized, of which the supersonic wave measurement was carried out under different confining pressure. According to the elasticity theory, the dynamic elastic parameters were obtained using the measured ultrasonic wave velocity. The results show that compressional and shear waves increase with the confining pressure and hydrate saturation increasing, and so the dynamic elastic modulus is.
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Singh, Harpreet, Evgeniy M. Myshakin, and Yongkoo Seol. "A Nonempirical Relative Permeability Model for Hydrate-Bearing Sediments." SPE Journal 24, no. 02 (August 28, 2018): 547–62. http://dx.doi.org/10.2118/193996-pa.
Full textAbstract:
Summary There are currently two types of relative permeability models that are used to model gas production from hydrate-bearing sediments: fully empirical parameter-fitting models [such as the University of Tokyo model (Masuda et al. 1997) and the Brooks and Corey model (Brooks and Corey 1964)] and partially empirical models [such as the Kozeny and Carman model (Wyllie and Gardner 1958) and capillary-tube-based models that assume only a single phase]. This study proposes an analytical model to estimate relative permeability of gas and water in a hydrate-bearing porous medium without curve fitting or use of any empirical parameters. The model is derived by conserving the momentum balance with the steady-state form of the Navier-Stokes equation for gas/water flow in a hydrate-bearing porous medium. The model is validated against a number of laboratory studies and is shown to perform better than most empirical models over a full range of experimental data. The proposed model is an analytical function of rock properties (average pore size and shape, porosity, irreducible water saturation, and saturation of hydrate), fluid properties (gas/water saturations and viscosities), and the hydrate-growth pattern [pore filling (PF), wall coating (WC), and a combination of PF and WC]. The benefits of the proposed model include sensitivity analysis of relevant physical parameters on relative permeability and estimation of rock parameters (such as porosity, pore size, and residual water saturation) using inverse modeling. The model can also be used to estimate two-phase permeability in a permeable medium without hydrates. The proposed model was used to analyze the effects of pore shapes, the hydrate-growth pattern, variable gas saturation, and wettability on relative permeability. The sensitivity results produced by the proposed model were verified using observations from other studies that investigated similar problems using either experiments or computationally expensive pore-scale simulations.
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Chuvilin, Evgeny, Dinara Davletshina, Boris Bukhanov, Aliya Mukhametdinova, and Vladimir Istomin. "Formation of Metastability of Pore Gas Hydrates in Frozen Sediments: Experimental Evidence." Geosciences 12, no. 11 (November 14, 2022): 419. http://dx.doi.org/10.3390/geosciences12110419.
Full textAbstract:
The Arctic permafrost and zones of hydrate stability may evolve to the conditions that allow gas hydrates to remain metastable for a long time due to self-preservation within 150 m depths. The behavior of relict (metastable) gas hydrates in frozen sediments is controlled externally by pressure and temperature and internally by the properties of hydrate particles and sediments. The sensitivity of the dissociation and self-preservation of pore gas hydrates to different factors is investigated in laboratory experiments. The observations focus on time-dependent changes in methane hydrate saturation in frozen sand samples upon the pressure dropping below phase equilibrium in the gas–hydrate–ice system. The preservation of pore gas hydrates in these conditions mainly depends on the initial hydrate and ice saturation, clay contents and mineralogy, salinity, and texture of sediments, which affect the size, shape, and structure distortion of hydrate inclusions. The self-preservation mechanism works well at high initial contents of pore ice and hydrate, low salinity, relatively low percentages of clay particles, temperatures below −4 °C, and above-equilibrium pressures. Nuclear magnetic resonance (NMR) measurements reveal considerable amounts of unfrozen pore water in frozen sediments that may hold for several days after the pressure drop, which controls the dissociation and self-preservation processes. Metastable gas hydrates in frozen sand may occupy up to 25% of the pore space, and their dissociation upon permafrost thawing and pressure drops may release up to 16 m3 of methane into the atmosphere per 1 m3 of hydrate-bearing permafrost.
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Wang, Xiao-Hui, Qiang Xu, Ya-Nan He, Yun-Fei Wang, Yi-Fei Sun, Chang-Yu Sun, and Guang-Jin Chen. "The Acoustic Properties of Sandy and Clayey Hydrate-Bearing Sediments." Energies 12, no. 10 (May 14, 2019): 1825. http://dx.doi.org/10.3390/en12101825.
Full textAbstract:
Natural gas hydrates samples are rare and difficult to store and transport at in situ pressure and temperature conditions, resulting in difficulty to characterize natural hydrate-bearing sediments and to identify hydrate accumulation position and saturation at the field scale. A new apparatus was designed to study the acoustic properties of seafloor recovered cores with and without hydrate. To protect the natural frames of recovered cores and control hydrate distribution, the addition of water into cores was performed by injecting water vapor. The results show that hydrate saturation and types of host sediments are the two most important factors that govern the elastic properties of hydrate-bearing sediments. When gas hydrate saturation adds approximately to 5–25%, the corresponding P-wave velocity (Vp) increases from 1.94 to 3.93 km/s and S-wave velocity (Vs) increases from 1.14 to 2.23 km/s for sandy specimens; Vp and Vs for clayey samples are 1.72–2.13 km/s and 1.10–1.32 km/s, respectively. The acoustic properties of sandy sediments can be significantly changed by the formation/dissociation of gas hydrate, while these only minorly change for clayey specimens.
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Ning, Fu Long, Yi Bing Yu, Guo Sheng Jiang, Xiang Wu, Ke Ni Zhang, Ling Zhang, and Li Liu. "Numerical Simulations of Drilling Mud Invasion into the Marine Gas Hydrate-Bearing Sediments." Advanced Materials Research 366 (October 2011): 378–87. http://dx.doi.org/10.4028/www.scientific.net/amr.366.378.
Full textAbstract:
When drilling through the oceanic gas hydrate-bearing sediments, the water-based mud under overbalanced drilling condition will invade into the borehole sediments. The invasion behavior can influence the hydrate stability, wellbore stability and well logging evaluation. In this work, we performed the numerical simulations to study the effects of density (i.e., corresponding pressure), temperature and salinity of mud on the mud invasion and hydrate stability around borehole. The results show that the mud invasion will promote greatly the hydrate dissociation near wellbore sediments if the temperature of mud is higher than that of hydrate stability. Under certain conditions, the higher mud density, temperature and salinity, the greater degree of mud invasion and heat transfer, and the more hydrate dissociation. The gas produced from hydrate dissociation can reform hydrates again in the sediments, and even the hydrate saturation is higher than that in situ sediments due to the displacing effect of the mud invasion, which forms a high-saturation hydrate girdle band around the borehole.
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JAKOBSEN, M., T. A. JOHANSEN, and B. O. RUUD. "MODELED VELOCITY AND REFLECTIVITY PROPERTIES OF ANISOTROPIC HYDRATED SEDIMENTS." Journal of Computational Acoustics 09, no. 04 (December 2001): 1507–22. http://dx.doi.org/10.1142/s0218396x01001029.
Full textAbstract:
The potential of mapping the extent gas hydrate from seismic data relies on the micromechanical model linking the actual material properties to the relevant observational data. We here consider four-phase sediment models consisting of hydrate, fluid, quartz (grains) and clay (platelets). The hydrate may occur in two ways when the pore volume is partially saturated, either in the pore voids without grain contact (unconnected), or as a grain coating, i.e. acting as a cementation of the grains (connected). In this model, the spatial orientations of the clay platelets are taken into account. By considering a model with a dominant horizontal grain distribution, we find that the elastic stiffnesses and velocities increase with an increasing proportion of hydrate. Both P and S velocities are largest for connected hydrates. Furthermore, the P wave anisotropy is largest for connected hydrates, while the S wave anisotropy is largest for the unconnected hydrates. If we consider the hydrate model as unconnected for low saturation (less than 50%) and connected for higher saturation, the reflectivity properties of the bottom simulating reflector (BSR) are similar to those found by other investigators considering no preferred grain orientation.
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Khasanov, Marat K., Svetlana R. Kildibaeva, Maxim V. Stolpovsky, and Nail G. Musakaev. "Mathematical Model of the Process of Non-Equilibrium Hydrate Formation in a Porous Reservoir during Gas Injection." Mathematics 10, no. 21 (November 1, 2022): 4054. http://dx.doi.org/10.3390/math10214054.
Full textAbstract:
Increasing the efficiency of natural gas storage in geological formations is possible by transferring gas from a free state to a gas hydrate state, since gas hydrates have a number of unique properties. For example, 1 m3 of methane hydrate contains 164 m3 of gas under normal conditions. It is possible to store a sufficiently large amount of gas in a small volume at a relatively low pressure. To study the regularities of the process of formation of underground gas hydrate gas storage, this article presents a mathematical model of the process of methane injection into a natural reservoir saturated with methane and water, accompanied by the formation of gas hydrate. Unlike previous works, the constructed mathematical model additionally takes into account a number of factors: the filtration flow of water, the real gas properties, the Joule–Thomson effects and adiabatic compression. The process of gas hydrate formation is considered as a non-equilibrium phase transition. Numerical solutions of the problem are constructed that describe the distributions of parameters (temperature, pressure, phase saturations) in a reservoir. Dependences are obtained that reveal the regularities of the process of non-equilibrium formation of gas hydrate in a natural reservoir during gas injection. The influence of gas injection pressure and temperature, as well as reservoir porosity and permeability, on the distributions of pressure, temperature, water saturation and hydrate saturation in the reservoir, as well as on the dynamics of changes in these parameters and the mass of gas hydrate formed in the reservoir over time, are analyzed.
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Yan, Mengqiu, Rongtao Yan, and Haihao Yu. "Strain-Softening Characteristics of Hydrate-Bearing Sediments and Modified Duncan–Chang Model." Advances in Materials Science and Engineering 2021 (December 17, 2021): 1–15. http://dx.doi.org/10.1155/2021/2809370.
Full textAbstract:
Marine hydrate exploitation may trigger the seabed geological disaster, such as seafloor collapse and landslide. It is critically important to understand the mechanical properties of hydrate-bearing sediment. Strain-softening observation is a typical behavior of hydrate-bearing sediment (HBS) and exhibits more significant at higher hydrate saturation. This paper performed a series of triaxial compression tests on methane hydrate-bearing sand to analyze the influence rule and mechanism of hydrate saturation on the strain-softening characteristic, stiffness, and strength and introduced the strain-softening index to quantificationally characterize the strain-softening behaviors of HBS with different hydrate saturations. Based on the analyses on the mechanical behavior of HBS, the Duncan–Chang model is extended to address the stress-strain curves of HBS. Two empirical formulas with hydrate saturation embedded are used to characterize the enhanced initial modulus and strength for HBS, respectively. To address the strain-softening behavior of HBS, the modified Duncan–Chang model introduced a damage factor into the strength of HBS. To validate the modified Duncan–Chang model, four different triaxial compression tests are simulated. The good consistence between simulated result and experimental data demonstrates that the modified Duncan–Chang model is capable of reflecting the influence of hydrate saturation not only on the stiffness and strength but also on the strain-softening characteristics of HBS.
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Yakushev, Vladimir. "Experimental Modeling of Methane Hydrate Formation and Decomposition in Wet Heavy Clays in Arctic Regions." Geosciences 9, no. 1 (December 27, 2018): 13. http://dx.doi.org/10.3390/geosciences9010013.
Full textAbstract:
Experimental studies on clay sample saturation by methane hydrates proved that clay particles play an important role in the hydrate accumulation and decomposition processes in sediments. Depending on water content, the same clay mineral can serve as inhibitor, neutral component and promoter of hydrate formation. Wet clay is a good mineral surface for hydrate formation, but clays represent the worst media for hydrate accumulation and existence. Nevertheless, there are many observations of hydrate presence in clay-containing sediments, especially offshore. Experimental modelling of metastable hydrate decomposition in sediment samples recovered from permafrost in “Yamal crater” in the Russian Arctic has shown that metastable hydrates located in frozen, salted clays can generate huge volumes of gas, even with a negligible (tenth and hundredth of a degree) temperature rise.
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Sobisevich, A. L., E. I. Suetnova, and R. A. Zhostkov. "Evolution of gas hydrates accumulation in zones of submarine mud volcanoes." Вулканология и сейсмология, no. 2 (April 21, 2019): 45–51. http://dx.doi.org/10.31857/s0203-03062019245-51.
Full textAbstract:
The article examines the processes of evolution of gas hydrate accumulations, related to submarine mud volcanoes. A mathematical model and the results of numerical modeling of the accumulation of gas hydrates in the seabed in the deep structures of underwater mud volcanoes are presented.
Numerical analysis of the influence held feeder layer depth and pressure therein to the evolution of gas hydrate saturation confined to deep water mud volcanoes were performed. Modeling quantitatively showed that hydrate saturation in areas of underwater mud volcanoes is not constant and its evolution depends on the geophysical properties of the bottom medium (temperature gradient, porosity, permeability, physical properties of sediments) and the depth of the supply reservoir and pressure in it, and the rate of hydrate accumulation in tens and hundreds times the rate of hydrate accumulation in the sedimentary basins of passive continental margin.
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Sobisevich, A. L., E. I. Suetnova, and R. A. Zhostkov. "Evolution of gas hydrates accumulation in zones of submarine mud volcanoes." Вулканология и сейсмология, no. 2 (April 21, 2019): 45–51. http://dx.doi.org/10.31857/s0205-96142019245-51.
Full textAbstract:
The article examines the processes of evolution of gas hydrate accumulations, related to submarine mud volcanoes. A mathematical model and the results of numerical modeling of the accumulation of gas hydrates in the seabed in the deep structures of underwater mud volcanoes are presented.
Numerical analysis of the influence held feeder layer depth and pressure therein to the evolution of gas hydrate saturation confined to deep water mud volcanoes were performed. Modeling quantitatively showed that hydrate saturation in areas of underwater mud volcanoes is not constant and its evolution depends on the geophysical properties of the bottom medium (temperature gradient, porosity, permeability, physical properties of sediments) and the depth of the supply reservoir and pressure in it, and the rate of hydrate accumulation in tens and hundreds times the rate of hydrate accumulation in the sedimentary basins of passive continental margin.
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Zhang, Zhen Guo, Lian Feng Gao, Ying Zhang, Yu Wang, Guo Yuan Shi, and Chang Shui Liu. "Mechanism of Frequency Conversion Vibration Stimulating Exploiting Technology with Marine Gas Hydrate and its Numerical Simulation." Advanced Materials Research 201-203 (February 2011): 413–16. http://dx.doi.org/10.4028/www.scientific.net/amr.201-203.413.
Full textAbstract:
Gas hydrate is a new energy in the 21st century with the characteristics of high energy density, huge amount of resources and cleaning. It has important significances for resources development, environmental protection and global climate changing. Due to the limitations of the occurrence mode and the technical level of marine gas hydrates, at present, the development and utilization of the resources are still tentative. This article analyzed and evaluated several key technologies to develop marine gas hydrates, that is depressurization, thermal methods, chemical injection method, CO2 replacement method, and fluorine gas+microwave method. However, these methods are difficult to control in the mining process. The research based on the properties of the occurrence of marine gas hydrate, used the principle of gas hydrate decomposition caused by vibration, by adjusting the excitation intensity, frequency, and amplitude. Different local oscillator strength applied on the Occurrence of gas hydrate layer. Gas hydrate stable state changed in mining region, prompting the gas hydrate conversing from solid to gas. Numerical simulations show: Low-frequency vibration should be used in the layers with higher hydrate saturation. The vibration frequency should be improved in the layers with lower hydrate saturation. The method has a good controllability for the region and the process of mining, avoiding geological disasters and environmental issues in the seabed caused by the mining process losing control.
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Li, Nan, Rezeye Rehemituli, Jie Zhang, and Changyu Sun. "One-Dimensional Study on Hydrate Formation from Migrating Dissolved Gas in Sandy Sediments." Energies 13, no. 7 (March 30, 2020): 1570. http://dx.doi.org/10.3390/en13071570.
Full textAbstract:
Upward migration of gas-dissolved pore fluid is an important mechanism for many naturally occurring hydrate reservoirs. However, there is limited understanding in this scenario of hydrate formation in sediments. In this preliminary work, hydrate formation and accumulation from dissolved gas in sandy sediments along the migration direction of brine was investigated using a visual hydrate simulator. Visual observation was employed to capture the morphology of hydrates in pores through three sapphire tubes. Meanwhile, the resistivity evolution of sediments was detected to characterize hydrate distribution in sediments. It was observed that hydrates initially formed as a thin film or dispersed crystals and then became a turbid colloidal solution. With hydrate growth, the colloidal solution converted to massive solid hydrates. Electrical resistivity experienced a three-stage evolution process corresponding to the three observed hydrate morphologies. The results of resistivity analysis also indicated that the bottom–up direction of hydrate growth was consistent with the flow direction of brine, and two hydrate accumulation centers successively appeared in the sediments. Hydrates preferentially formed and accumulated in certain depths of the sediments, resulting in heterogeneous hydrate distribution. Even under low saturation, the occurrence of heterogeneous hydrates led to the sharp reduction of sediment permeability.
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Ojha, Maheswar, and Ranjana Ghosh. "Assessment of gas hydrate using prestack seismic inversion in the Mahanadi Basin, offshore eastern India." Interpretation 9, no. 2 (March 11, 2021): SD15—SD26. http://dx.doi.org/10.1190/int-2020-0139.1.
Full textAbstract:
The Indian National Gas Hydrate Program Expedition-01 in 2006 has discovered gas hydrate in the Mahanadi offshore basin along the eastern Indian margin. However, well-log analysis, pressure core measurements, and infrared anomalies reveal that gas hydrates are distributed as disseminated within the fine-grained sediment, unlike massive gas hydrate deposits in the Krishna-Godavari Basin. The 2D multichannel seismic section, which crosses holes NGHP-01-9A and 19B located at approximately 24 km apart, indicates a continuous bottom-simulating reflector (BSR) along it. We aim to investigate the prospect of gas hydrate accumulation in this area by integrating well-log analysis and seismic methods with rock-physics modeling. First, we estimate gas hydrate saturation at these two holes from the observed impedance using the three-phase Biot-type equation. Then, we establish a linear relationship between the gas hydrate saturation and the impedance contrast with respect to the water-saturated sediment. Using this established relation and impedance obtained from prestack inversion of seismic data, we produce a 2D gas hydrate-distribution image over the entire seismic section. The gas hydrate saturation estimated from resistivity and sonic data at well locations varies within 0%–15%, which agrees well with the available pressure core measurements at hole 19. However, the 2D map of gas hydrate distribution obtained from our method indicates that the maximum gas hydrate saturation is approximately 40% just above the BSR between the common-depth points of 1450 and 2850. The presence of gas-charged sediments below the BSR is one of the reasons for the strong BSR observed in the seismic section, which is depicted as low impedance in the inverted impedance section. Closed sedimentary structures above the BSR are probably obstructing the movements of free-gas upslope, for which we do not see the presence of gas hydrate throughout the seismic section above the BSR.
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Pallipurath, Mohamed Iqbal. "Dissociation and Subsidence of Hydrated Sediment: Coupled Models." Energy Exploration & Exploitation 27, no. 2 (April 2009): 105–31. http://dx.doi.org/10.1260/0144-5987.27.2.105.
Full textAbstract:
Thermal dissociation of hydrated sediment by a pumped hot fluid is modeled. A radial heat flow from the hot pipe is assumed. The coordinate system is cylindrical. Three components (hydrate, methane and water) and three phases (hydrate, gas, and aqueous-phase) are considered in the simulator. The intrinsic kinetics of hydrate formation or dissociation is considered using the Kim-Bishnoi model. Mass transport, including two-phase flow, molecular diffusions and heat transfer involved in formation or dissociation of hydrates are included in the governing equations, which are discretized with finite volume difference method and are solved in an explicit manner. The strength deterioration of the hydrate bed as a result of dissociation is investigated with a geo-mechanical model. The way in which dissociation affects the bed strength is determined by plugging in the porosity and saturation change as a result of dissociation into the sediment collapse equations. A mechanism to measure the pore pressure changes occurring due to dissociation is developed. The rate of collapse as dissociation proceeds is determined and the model thus enables the definition of a safety envelope for gas hydrate drilling.
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Lu, Xiaobing, Xuhui Zhang, Fangfang Sun, Shuyun Wang, Lele Liu, and Changling Liu. "Experimental Study on the Shear Band of Methane Hydrate-Bearing Sediment." Journal of Marine Science and Engineering 9, no. 11 (October 21, 2021): 1158. http://dx.doi.org/10.3390/jmse9111158.
Full textAbstract:
The occurrence of a shear band is often thought as the precursor of failure. To study the initiation of shear banding in gas hydrate-bearing sediments, two groups of triaxial compression tests combined with a CT (computer tomography) scan were conducted by triaxial CT-integrated equipment under two confining pressures and seven hydrate saturations. The macro stress–strain curves and the corresponding CT scanning images of the micro-structure and the distribution of the components were obtained. The geometric parameters of the shear bands were measured based on the CT images at four typical axial strains, respectively. The distribution characteristics of soil particles, water, hydrate and gas were also analyzed. It is shown that the existence of methane hydrate changes the mechanical property of hydrate-bearing sediment from plastic failure to brittle failure when the hydrate saturation is over 13%, which occurs in the range of the tests in this paper. The peak of the deviatoric stress increases with the hydrate saturation. The shear band is in either a single oblique line or inter-cross lines depending on the hydrate saturation, the effective confining pressure and the initial distribution of the gas hydrate. Most of the shear band surfaces are not straight, and the widths of the shear bands are almost non-uniformly distributed.
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Heeschen, K., M. Haeckel, I. Klaucke, M. K. Ivanov, and G. Bohrmann. "Quantifying in-situ gas hydrates at active seep sites in the eastern Black Sea using pressure coring technique." Biogeosciences Discussions 8, no. 3 (May 9, 2011): 4529–58. http://dx.doi.org/10.5194/bgd-8-4529-2011.
Full textAbstract:
Abstract. In the eastern Black Sea, we determined methane (CH4) concentrations, gas hydrate volumes and their vertical distribution from combined gas and chloride (Cl−) measurements within pressurized sediment cores. The total gas volume collected from the cores corresponds to concentrations of 1.2–1.4 mol of methane per kg porewater at in-situ pressure, which is equivalent to a gas hydrate saturation of 15–18% of pore volume and amongst the highest values detected in shallow seep sediments. At the central seep site, a high-resolution Cl− profile resolves the upper gas hydrate stability boundary and a continuous layer of hydrates in a sediment column of 120 cm thickness. Including this information, a more precise gas hydrate saturation of 22–24% pore volume can be calculated. This is higher in comparison to a saturation calculated from the Cl− profile alone, resulting in 14.4%. The likely explanation is an active gas hydrate formation from CH4 gas ebullition. The hydrocarbons at Batumi Seep are of shallow biogenic origin (CH4 > 99.6%), at Pechori Mound they originate from deeper thermocatalytic processes as indicated by the lower ratios of C1 to C2–C3 and the presence of C5.
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Heeschen, K. U., M. Haeckel, I. Klaucke, M. K. Ivanov, and G. Bohrmann. "Quantifying in-situ gas hydrates at active seep sites in the eastern Black Sea using pressure coring technique." Biogeosciences 8, no. 12 (December 8, 2011): 3555–65. http://dx.doi.org/10.5194/bg-8-3555-2011.
Full textAbstract:
Abstract. In the eastern Black Sea, we determined methane (CH4) concentrations, gas hydrate volumes, and their vertical distribution from combined gas and chloride (Cl−) measurements within pressurized sediment cores. The total gas volume collected from the cores corresponded to concentrations of 1.2–1.4 mol CH4 kg−1 porewater at in-situ pressure, which is equivalent to a gas hydrate saturation of 15–18% of pore volume and amongst the highest values detected in shallow seep sediments. At the central seep site, a high-resolution Cl− profile resolved the upper boundary of gas hydrate occurrence and a continuous layer of hydrates in a sediment column of 120 cm thickness. Including this information, a more precise gas hydrate saturation of 22–24% pore volume could be calculated. This volume was higher in comparison to a saturation calculated from the Cl− profile alone, resulting in only 14.4%. The likely explanation is an active gas hydrate formation from CH4 gas ebullition. The hydrocarbons at Batumi Seep are of shallow biogenic origin (CH4 > 99.6%), at Pechori Mound they originate from deeper thermocatalytic processes as indicated by the lower ratios of C1 to C2–C3 and the presence of C5.
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Li, Chuanhui, and Xuewei Liu. "Research on the Estimate of Gas Hydrate Saturation Based on LSTM Recurrent Neural Network." Energies 13, no. 24 (December 11, 2020): 6536. http://dx.doi.org/10.3390/en13246536.
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Gas hydrate saturation is an important index for evaluating gas hydrate reservoirs, and well logs are an effective method for estimating gas hydrate saturation. To use well logs better to estimate gas hydrate saturation, and to establish the deep internal connections and laws of the data, we propose a method of using deep learning technology to estimate gas hydrate saturation from well logs. Considering that well logs have sequential characteristics, we used the long short-term memory (LSTM) recurrent neural network to predict the gas hydrate saturation from the well logs of two sites in the Shenhu area, South China Sea. By constructing an LSTM recurrent layer and two fully connected layers at one site, we used resistivity and acoustic velocity logs that were sensitive to gas hydrate as input. We used the gas hydrate saturation calculated by the chloride concentration of the pore water as output to train the LSTM network. We achieved a good training result. Applying the trained LSTM recurrent neural network to another site in the same area achieved good prediction of gas hydrate saturation, showing the unique advantages of deep learning technology in gas hydrate saturation estimation.
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Diao, Haoyu, Honghai Fan, Rongyi Ji, Bangchen Wu, Yuguang Ye, Yuhan Liu, Fei Zhou, Yixiang Yang, and Zhi Yan. "P-Y Curve Correction of Shallow Seabed Formation Containing Hydrate." Energies 16, no. 7 (April 6, 2023): 3274. http://dx.doi.org/10.3390/en16073274.
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With the continuous growth in global energy demand, the exploration and development of hydrates has been the focus of increasing attention, and the accurate evaluation of the mechanical properties of hydrate layers has become particularly important. In this study, using a self-developed hydrate sample preparation device and hydrate triaxial seepage test platform, triaxial shear tests were carried out using the in situ synthesis method for hydrate sediment in the laboratory, and the stress–strain curves of hydrate sediment with different levels of saturation were obtained. By analyzing the stress–strain curve, the mechanical parameters of hydrate sediment were calculated and simulated using ABAQUS (2021, Dassault systemes, Vélizy Villacoublay France) finite element software. Several p-y curves were calculated and compared with the simulation results, and the p-y curve correction method of the hydrate layer in a shallow seabed was obtained. It was found that the strength of the hydrate sediment increased with an increase in saturation. At the same time, an increase in confining pressure and a decrease in temperature also increased the strength of hydrate deposits. Through comparison with the existing API (American Petroleum Institute) standard p-y curve, it was found that its strength is low because the existence of the hydrate improves the formation strength.
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Moridis, George J., and Michael Brendon Kowalsky. "Response of Oceanic Hydrate-Bearing Sediments to Thermal Stresses." SPE Journal 12, no. 02 (June 1, 2007): 253–68. http://dx.doi.org/10.2118/111572-pa.
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Summary In this study, we evaluate the response of oceanic subsurface systems to thermal stresses caused by the flow of warm fluids through noninsulated well systems crossing hydrate-bearing sediments. Heat transport from warm fluids, originating from deeper reservoirs under production, into the geologic media can cause dissociation of the gas hydrates. The objective of this study is to determine whether gas evolution from hydrate dissociation can lead to excessive pressure buildup, and possibly to fracturing of hydrate-bearing formations and their confining layers, with potentially adverse consequences on the stability of the suboceanic subsurface. This study also aims to determine whether the loss of the hydrate—known to have a strong cementing effect on the porous media—in the vicinity of the well, coupled with the significant pressure increases, can undermine the structural stability of the well assembly. Scoping 1D simulations indicated that the formation intrinsic permeability, the pore compressibility, the temperature of the produced fluids and the initial hydrate saturation are the most important factors affecting the system response, while the thermal conductivity and porosity (above a certain level) appear to have a secondary effect. Large-scale simulations of realistic systems were also conducted, involving complex well designs and multilayered geologic media with nonuniform distribution of properties and initial hydrate saturations that are typical of those expected in natural oceanic systems. The results of the 2D study indicate that although the dissociation radius remains rather limited even after long-term production, low intrinsic permeability and/or high hydrate saturation can lead to the evolution of high pressures that can threaten the formation and its boundaries with fracturing. Although lower maximum pressures are observed in the absence of bottom confining layers and in deeper (and thus warmer and more pressurized) systems, the reduction is limited. Wellbore designs with gravel packs that allow gas venting and pressure relief result in substantially lower pressures. Introduction Background. Gas hydrates are solid crystalline compounds in which gas molecules (referred to as guests) are lodged within the lattices of ice crystals (called hosts). Under suitable conditions of low temperature and high pressure, a gas G will react with water to form hydrates according to (Eq.) where NH is the hydration number. Of particular interest are hydrates formed by hydrocarbon gases when G is an alkane. Natural hydrates in geological systems also include CO2, H2S, and N2 as guests. Vast amounts of hydrocarbons are trapped in hydrate deposits (Sloan 1998). Such deposits occur in two distinctly different geologic settings where the necessary low temperatures and high pressures exist for their formation and stability: in the permafrost and in deep ocean sediments. The three main methods of hydrate dissociation are (Sloan 1998):depressurization, in which the pressure P is lowered to a level lower than the hydration pressure Pe at the prevailing temperature T,thermal stimulation, in which T is raised above the hydration temperature Te at the prevailing P, andthe use of inhibitors (such as salts and alcohols), which causes a shift in the Pe -Te equilibrium through competition with the hydrate for guest and host molecules. Dissociation results in the production of gas and water, with a commensurate reduction in the saturation of the solid hydrate phase. Gas hydrates exist in many configurations below the sea floor, including massive (thick solid zones), continuous layers, nodular, and disseminated, each of which may affect the seafloor stability differently. The hydrates in all of these configurations may be part of the solid skeleton that supports overlying sediments, which ultimately support platforms and pipelines needed for production from conventional oil and gas resources, and from hydrate accumulations (when it becomes economically and technically viable).
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Li, Chuanhui, Kai Feng, and Xuewei Liu. "Study on p-Wave Attenuation in Hydrate-Bearing Sediments Based on BISQ Model." Journal of Geological Research 2013 (October 9, 2013): 1–8. http://dx.doi.org/10.1155/2013/176579.
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In hydrate-bearing sediments, the elastic wave attenuation characteristics depend on the elastic properties of the sediments themselves on the one hand, and on the other hand, they also depend on the hydrate occurrence state and hydrate saturation. Since the hydrate-bearing sediments always have high porosity, so they show significant porous medium characteristics. Based on the BISQ porous medium model which is the most widely used model to study the attenuation characteristics in the porous media, we focused on p-wave attenuation in hydrate-bearing sediments in Shenhu Area, South China Sea, especially in specific seismic frequency range, which lays a foundation for the identification of gas hydrates by using seismic wave attenuation in Shenhu Area, South China Sea. Our results depict that seismic wave attenuation is an effective attribute to identify gas hydrates.
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Almenningen, Stian, Per Fotland, and Geir Ersland. "Magnetic Resonance Imaging of Methane Hydrate Formation and Dissociation in Sandstone with Dual Water Saturation." Energies 12, no. 17 (August 22, 2019): 3231. http://dx.doi.org/10.3390/en12173231.
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This paper reports formation and dissociation patterns of methane hydrate in sandstone. Magnetic resonance imaging spatially resolved hydrate growth patterns and liberation of water during dissociation. A stacked core set-up using Bentheim sandstone with dual water saturation was designed to investigate the effect of initial water saturation on hydrate phase transitions. The growth of methane hydrate (P = 8.3 MPa, T = 1–3 °C) was more prominent in high water saturation regions and resulted in a heterogeneous hydrate saturation controlled by the initial water distribution. The change in transverse relaxation time constant, T2, was spatially mapped during growth and showed different response depending on the initial water saturation. T2 decreased significantly during growth in high water saturation regions and remained unchanged during growth in low water saturation regions. Pressure depletion from one end of the core induced a hydrate dissociation front starting at the depletion side and moving through the core as production continued. The final saturation of water after hydrate dissociation was more uniform than the initial water saturation, demonstrating the significant redistribution of water that will take place during methane gas production from a hydrate reservoir.
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Vasheghani Farahani, Mehrdad, Aliakbar Hassanpouryouzband, Jinhai Yang, and Bahman Tohidi. "Development of a coupled geophysical–geothermal scheme for quantification of hydrates in gas hydrate-bearing permafrost sediments." Physical Chemistry Chemical Physics 23, no. 42 (2021): 24249–64. http://dx.doi.org/10.1039/d1cp03086h.
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In this article, a coupled geophysical–geothermal scheme has been developed to predict hydrates saturation in gas hydrate-bearing permafrost sediments via utilising their geophysical and geothermal responses.
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Tharimela, Raghava, Adolpho Augustin, Marcelo Ketzer, Jose Cupertino, Dennis Miller, Adriano Viana, and Kim Senger. "3D controlled-source electromagnetic imaging of gas hydrates: Insights from the Pelotas Basin offshore Brazil." Interpretation 7, no. 4 (November 1, 2019): SH111—SH131. http://dx.doi.org/10.1190/int-2018-0212.1.
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Mapping of natural gas hydrate systems has been performed successfully in the past using the controlled-source electromagnetic (CSEM) method. This method relies on differentiating resistive highly saturated free gas or hydrate-bearing host sediment from a less resistive low-saturated gas or brine-bearing host sediments. Knowledge of the lateral extent and resistivity variations (and hence the saturation variations) within sediments that host hydrates is crucial to be able to accurately quantify the presence of saturated gas hydrates. A 3D CSEM survey (PUCRS14) was acquired in 2014 in the Pelotas Basin offshore Brazil, with hydrate resistivity mapping as the main objective. The survey was acquired within the context of the CONEGAS research project, which investigated the origin and distribution of gas hydrate deposits in the Pelotas Basin. We have inverted the acquired data using a proprietary 3D CSEM anisotropic inversion algorithm. Inversion was purely CSEM data driven, and we did not include any a priori information in the process. Prior to CSEM, interpretation of near-surface geophysical data including 2D seismic, sub-bottom profiler, and multibeam bathymetry data indicated possible presence of gas hydrates within features identified such as faults, chimneys, and seeps leading to pockmarks, along the bottom simulating reflector and within the gas hydrate stability zone. Upon integration of the same with CSEM-derived resistivity volume, the interpretation revealed excellent spatial correlation with many of these features. The interpretation further revealed new features with possible hydrate presence, which were previously overlooked due to a lack of a clear seismic and/or multibeam backscatter signature. In addition, features that were previously mapped as gas hydrate bearing had to be reinterpreted as residual or low-saturated gas/hydrate features, due to the lack of significant resistivity response associated with them. Furthermore, we used the inverted resistivity volume to derive the saturation volume of the subsurface using Archie’s equation.
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Qiu, Yue, Xiangfu Wang, Zhaofeng Wang, Wei Liang, and Tongbin Zhao. "THMC Fully Coupled Model of Natural Gas Hydrate under Damage Effect and Parameter Sensitivity Analysis." Journal of Marine Science and Engineering 11, no. 3 (March 13, 2023): 612. http://dx.doi.org/10.3390/jmse11030612.
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In order to study the influence of damage on the gas production of natural gas hydrate, a multi-physical field theoretical model considering damage effect and coupling thermal-hydraulic-mechanical-chemical (THMC) was established by theoretical analysis and numerical simulation. The THMC model establishes the relationship between the elastic modulus of hydrate sediment and hydrate saturation during the whole process of hydrate decomposition. The THC (thermal-hydraulic-chemical) and THMC fully coupled models not considering or considering the damage effect were compared and analyzed, and the reliability of the THMC fully coupled model was verified. On this basis, the deformation, permeability and damage of hydrate sediments under different initial hydrate saturations and different depressurization amplitudes, as well as the hydrate gas production rate and cumulative gas production, are analyzed. The results showed that higher initial hydrate saturation inhibited the development of damage, maintained stable gas production and increased cumulative gas production. Larger depressurization promoted damage and increased cumulative gas production, but it was easy to cause stability problems.