Academic literature on the topic 'Dual contact zone'
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Journal articles on the topic "Dual contact zone"
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Tran, Van Bon. "Dual finite element analysis for contact problem of elastic bodies with an enlarging contact zone." Applications of Mathematics 31, no. 5 (1986): 345–64. http://dx.doi.org/10.21136/am.1986.104213.
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Härke, Heinrich. "Through a Black Hole into Parallel Universes." Ancient Civilizations from Scythia to Siberia 26, no. 2 (December 18, 2020): 413–24. http://dx.doi.org/10.1163/15700577-12341383.
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Abstract The Anglo-Saxon immigration of the 5th-6th centuries AD led to a dual contact situation in the British Isles: with the native inhabitants of the settlement areas in south-eastern England (internal contact zone), and with the Celtic polities outside the Anglo-Saxon areas (external contact zone). In the internal contact zone, social and ethnogenetic processes resulted in a complete acculturation of the natives by the 9th century. By contrast, the external contact zone between Anglo-Saxon and Celtic polities resulted in a cultural and linguistic split right across the British Isles up to the 7th century, and arguably well beyond. The cultural boundary between these two domains became permeable in the 7th century as a consequence of Anglo-Saxon Christianization which created a northern communication zone characterized by a distinct art style (Insular Art). In the early medieval British Isles, contact resulting from migration did not lead to cultural exchange for about two centuries, and it took profound ideological and social changes to establish a basis for communication.
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Yu, Yan, Rong Ji Zhou, and Feng Xue Wang. "Numerical Simulation of the Temperature Field During DP1000 Dual-Phase Steel Resistance Spot Welding." Advanced Materials Research 391-392 (December 2011): 666–71. http://dx.doi.org/10.4028/www.scientific.net/amr.391-392.666.
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Dual phase steel resistance spot welding process is transient, rapid, invisible, complex, which makes the physical process of welding not yet be fully understood. Both the preprocessing contact stress field and thermo - electric transient process under alternative current(AC)load of the resistance spot welding of DP1000 dual - phase steel are analyzed by ANSYS12.0 finite-element analysis software. The fusion zone formation process and the contact situation of electrode and workpiece, between workpieces, lamination surface is investigated through numerical simulation. The project can help understand the phenomenon and essence of the DP1000 spot welding optimize the structure design and process design, quality control, for the dual-phase steel in vehicle body spot welding quality control to provide theoretical guidance.
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Berre, Simon Le, Isabelle Ramière, Jules Fauque, and David Ryckelynck. "Condition Number and Clustering-Based Efficiency Improvement of Reduced-Order Solvers for Contact Problems Using Lagrange Multipliers." Mathematics 10, no. 9 (April 30, 2022): 1495. http://dx.doi.org/10.3390/math10091495.
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This paper focuses on reduced-order modeling for contact mechanics problems treated by Lagrange multipliers. The high nonlinearity of the dual solutions lead to poor classical data compression. A hyper-reduction approach based on a reduced integration domain (RID) is considered. The dual reduced basis is the restriction to the RID of the full-order dual basis, which ensures the hyper-reduced model to respect the non-linearity constraints. However, the verification of the solvability condition, associated with the well-posedness of the solution, may induce an extension of the primal reduced basis without guaranteeing accurate dual forces. We highlight the strong link between the condition number of the projected contact rigidity matrix and the precision of the dual reduced solutions. Two efficient strategies of enrichment of the primal POD reduced basis are then introduced. However, for large parametric variation of the contact zone, the reachable dual precision may remain limited. A clustering strategy on the parametric space is then proposed in order to deal with piece-wise low-rank approximations. On each cluster, a local accurate hyper-reduced model is built thanks to the enrichment strategies. The overall solution is then deeply improved while preserving an interesting compression of both primal and dual bases.
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Chang, Yoon Suk, Seong In Moon, Young Jin Kim, Jin Ho Lee, Myung Ho Song, and Young Hwan Choi. "Assessment of Steam Generator Tubes with Dual Axial Through-Wall Cracks." Solid State Phenomena 120 (February 2007): 71–76. http://dx.doi.org/10.4028/www.scientific.net/ssp.120.71.
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In this paper, conservatisms of current plugging criteria on steam generator tubes are reviewed and six new failure prediction models for dual through-wall cracks are proposed. In order to determine the optimum ones among these local or global failure prediction models, a series of plastic collapse tests and corresponding finite element analyses are carried out with respect to two adjacent axial through-wall cracks in thin plates. Then, reaction force model, plastic zone contact model and COD (Crack Opening Displacement) base model were selected as the optimum ones for integrity assessment of steam generator tubes with dual cracks.
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Cakir, Esin, Emre Ozlu, Mustafa Bakkal, and Erhan Budak. "Investigation of temperature distribution in orthogonal cutting through dual-zone contact model on the rake face." International Journal of Advanced Manufacturing Technology 96, no. 1-4 (January 18, 2018): 81–89. http://dx.doi.org/10.1007/s00170-017-1479-3.
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Wang, Meng-Jiao, and Yakov Kutsovsky. "Effect of Fillers on Wet Skid Resistance of Tires. Part II: Experimental Observations on Effect of Filler-Elastomer Interactions on Water Lubrication." Rubber Chemistry and Technology 81, no. 4 (September 1, 2008): 576–99. http://dx.doi.org/10.5254/1.3548221.
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Abstract It was demonstrated previously that on the worn surface of vulcanizates during wet skid tests, carbon black is covered by rubber whereas silica particles are at least partly exposed. In this report, the experimental results of the effects of carbon black and silica on wet skid resistance measured by various test methods and under different conditions are explained based on the “Three Zone Concept” of the contact area of tread compounds with the track surface during sliding or rolling. The three zones are water film squeezing, transition and traction zones. In the first two zones, where hydro-dynamic and micro-elastohydrodynamic lubrication mechanisms are dominant, silica is beneficial for wet friction. In the traction zone, where friction is governed by boundary lubrication, carbon black is preferred. Under test conditions where the water squeezing and transition zones are more developed, such as at high speed, lower temperature, smoother track surface, lower load, higher slip angle, and ABS brake, the silica shows better performance, but otherwise where the traction zone is larger, carbon black gives higher wet skid resistance. Accordingly, a new carbon-silica dual phase filler CSDPF 4210 that is characterized by high surface coverage with silica has been developed. With this material, the wet skid resistance of a passenger tire on a car with ABS at high speed and smooth road surface is significantly improved.
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Mao, Xinyu, Wei Liu, Yuanzhi Ni, and Valentin L. Popov. "Limiting shape of profile due to dual-mode fretting wear in contact with an elastomer." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, no. 9 (December 2, 2015): 1417–23. http://dx.doi.org/10.1177/0954406215619450.
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We consider fretting wear due to superimposed normal and tangential oscillations of two contacting bodies, one of which is an elastomer with a linear rheology. Similarly to the contact of elastic bodies, at small oscillation amplitudes, the wear occurs only in a circular slip zone at the border of the contact area and the wear profile tends to a limiting form, in which no further wear occurs. It is shown that under assumption of a constant coefficient of friction at the contact interface, the limiting form of the wear profile does depend neither on the particular wear criterion nor on the rheology of the elastomer and can be calculated analytically in a general form. The general calculation procedure and explicit analytic solutions for two initial forms, parabolic and conical, are presented for various combinations of frequencies and phases of normal and tangential oscillations as well as for various linear rheologies of the elastomer.
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Chen, Zuo Rong, and Shou Wen Yu. "Interaction between a Rigid Cylinder with a Piezoelectric Half-Space with Partial Adhesion." Advanced Materials Research 33-37 (March 2008): 333–38. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.333.
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An axisymmetric problem of interaction of a rigid rotating flat ended punch with a transversely isotropic linear piezoelectric half-space is considered. The contact zone consists of an inner circular adhesion region surrounded by an outer annular slip region with Coulomb friction. Beyond the contact region, the surface of the piezoelectric half-space is free from load. With the aid of the Hankel integral transform, this mixed boundary value problem is formulated as a system of dual integral equations. By solving the dual integral equations, analytical expressions for the tangential stress and displacement, and normal electric displacement on the surface of the piezoelectric half-space are obtained. An explicit relationship between the radius of the adhesion region, the angle of the rotation of the punch, material parameters, and the applied loads is presented. The obtained results are useful for characterization of piezoelectric materials by micro-indentation and micro-friction techniques.
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Punati, Venugopala Swami, Ishan Sharma, and Pankaj Wahi. "An exact dual-integral formulation of the indentation of finite, free-standing, end-supported adhesive elastic layers." Mathematics and Mechanics of Solids 24, no. 5 (July 18, 2018): 1294–319. http://dx.doi.org/10.1177/1081286518786069.
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We study indentation by a rigid cylindrical punch of finite, free-standing, adhesive elastic layers that are supported only at their ends. The adhesion is considered through an adhesive-zone model. Formulating the boundary-value problem, we obtain two coupled Fredholm integral equations of the first kind, which are solved by a collocation method. Results for non-adhesive contact are obtained when adhesion is zero, and they match well with our own finite element computations and earlier approximate analyses. Additionally, we obtain new results for deeper indentation of non-adhesive contact. In the limit of very adhesive and/or very soft solids, we formulate an approximate model similar to the well-known Johnson–Kendall–Roberts (JKR) model for half-spaces. Our results for adhesive contact match well with preliminary indentation experiments on adhesive layers. Finally, we demonstrate the utility of our approach in modelling structural adhesives through a specific example.
Dissertations / Theses on the topic "Dual contact zone"
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Behera, Bikash Chandra. "Some investigations on the turning of inconel 718 and modeling for cutting forces." Thesis, 2018. http://localhost:8080/iit/handle/2074/7578.
Full textBook chapters on the topic "Dual contact zone"
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Gunn, Geoffrey C. "The Ryukyu Trade Networks Revisited." In Imagined Geographies, 199–211. Hong Kong University Press, 2021. http://dx.doi.org/10.5790/hongkong/9789888528653.003.0010.
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It appears improbable but for several centuries corresponding to the European Middle Ages or the early Ming period in China, the Ryukyu Islands came to play a central role in connecting China to a range of Southeast Asian ports and polities. Commencing around 1373 the Kingdom began mounting complementary voyages to China, Japan, and Korea and so indirectly connected these polities with the Southeast Asia trade in tropical zone products. An important feature of the Ryukyu trade was its royal monopoly status. The Ryukyu connection with Ming China also fitted into the classic pattern of tribute trade, both ceremonially and commercially. First, the chapter explains the indispensable primary sources from which historians have pieced together Ryukyu’s long and distinctive history. A second section situates Ryukyu within the ambit and shadow of the Ming tribute trade. Third, it fits Ryukyu into the Korea trade. Fourth, and in some detail, the chapter examines the broad span of Ryukuan contacts with Southeast Asian ports and polities. Finally, it explains Ryukyu’s subordination to the Tokugawa bakufu and reinvention as a dual tributary stubbornly loyal to the Qing.
Conference papers on the topic "Dual contact zone"
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Yang, Bin, Min Chao Nie, Hong Shen, Yu Guo Li, Nian Da Xu, Hua Guo Zhang, and Cheng De Niu. "Newly-Developed Visualized Reservoir Characterization While Drilling Technology Improves Understanding of Complex Channel Sand, Assists EOR in a Mature Oilfield in Bo Hai Bay." In Offshore Technology Conference Asia. OTC, 2022. http://dx.doi.org/10.4043/31440-ms.
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Abstract PLxx oilfield is a mature oilfield which has been developed by horizontal wells for several years with water-injection production style. It features with shallow, complex, high challenging unconsolidated channel sand with lateral property variation due to pinch out, stacking or lamination. The thickness of pay zone changes from couple of to ten more meters which brings much high challenge to reservoir delineation while drilling and horizontal well placement execution. The oilfield locates at a faulted belt of Bo Hai Bay among which some small faults may happen. But it's difficult to be identified because of the low S/N ratio incurs from the shallow gas effect on the seismic data. Moreover, uneven flowing zone units exist within sandstone package due to dynamic reservoir production, uncertainty of lateral sand connections and possible inter-well interventions. As such, this makes the oil-water distribution more complicated and the oil-water contact isn't uniform in the sand package. In order to furtherly understand the complex channel sand, place the wellbore in the favorable sweet spot and enhance the oil recovery, a newly-developed visualized reservoir characterization while drilling integrated technology associated with RSS(rotary steerable system), HSVP(high speed data transmission system), RTC(remote transmission connection through Internet) and OSC(operation support center) was employed to optimize the operation efficiency during a three-wells drilling campaign in this oilfield. This newly-developed reservoir characterization technique is the industry innovative fully 9 components measuring azimuthal Electro-Magnetic propagation tool in one single sub. It provides not only the conventional propagation resistivity but also the geo-signal responses in a very quick, flexible way. In one of the case, the unique "Dual-diagonal orthogonal T-R antenna design" ensures the DOI (depth of investigation) as deep as 6.8meters. The reservoir boundaries such as the top, the bottom or the oil-water contact were distinctly characterized and the horizontal drainage section was precisely navigated within the profitable pay zone. The post-well reservoir characterization result is comparable with the seismic profile and very helpful to understand the dynamic reservoir flowing zone unit. The excellent performance is also reflected in the oil production; the initial oil production was increased from 40 m3/day to 69m3/day which is 75% higher than expected. Minimum 25% of oil recovery will be enhanced as forecast.
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Popovici, Violeta, Laura Bucur, Verginica Schroder, Aureliana Caraiane, and Victoria Badea. "STUDIES ON THE CYTOTOXIC POTENTIAL OF THE EXTRACT OF USNEA BARBATA (L.) F.H.WIGG." In NORDSCI International Conference. SAIMA Consult Ltd, 2020. http://dx.doi.org/10.32008/nordsci2020/b1/v3/29.
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Usnea barbata (L.) F.H.Wigg. is a fruticose lichen widespread in coniferous forests in the temperate zone of Europe and North America. The special dual structure of lichens, the result of the symbiosis between a fungus and an alga / cyanobacteria and the specific conditions in which they live, determine the synthesis of many special organic compounds - secondary metabolites - which ensure optimal protection against disturbing physical and biological factors. The present study aims to evaluate the cytotoxic activity of the extract of Usnea barbata (L.) F H Wigg. The cytotoxic activity was evaluated on the swimming larvae of Artemia salina L. The results was appreciated by the larvae mortality in contact with solutions of different concentrations of extract in dimethyl sulfoxide, comprised in the range 30 - 266 μg/mL; the highest mortality rate was obtained at 266 μg/mL. In conclusion, the present study shows that the extract of Usnea barbata (L.) F.H.Wigg. has cytotoxic properties; the cytotoxicity is directly proportional to the concentration of the applied extract solution.
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Prasun, Samir, and Andrew K. Wojtanowicz. "Probabilistic Estimation of Recovery From Naturally Fractured Bottom-Water Reservoir With Uncertain Well Placement in Fracture Network." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96836.
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Abstract In conventional reservoirs with bottom-water and no natural fractures, recovery can be predicted from known designed well spacing and completion placement. However, in naturally-fractured reservoirs (NFR), there is a considerable intrinsic uncertainty of such predictions because well’s completions may randomly intercept fractures (fracture-well) or be accidently placed in the matrix blocks (matrix-well) of NFR. Moreover, the recovery prediction is even more difficult when dual-completed wells with downhole water sink (DWS) are used for water coning control — with a second completion placed in the aquifer beneath the oil-water contact. The study compares recovery of the fracture and matrix-wells in the same NFR developed using single-completed and dual completed wells. The study also proposes a probabilistic method for finding well’s recovery in NFR having distributed fracture network and uncertain wells’s location in the network. Two patterns of fracture network are considered: densely-distributed natural fractures, and sparsely-distributed fracture clusters. DPDP Cartesian flow model is verified for estimation of recovery performance in each of the two networks using water cut patterns and ultimate recovery estimates. The model proves to be sufficiently accurate to be used in this study. The study considers ultimate recovery after 20 years of production, or when the water-cut value is 97%, for known or unknown well completion placement in the fracture network. In the latter case (uncertain completion placement), expected value of well’s recovery is computed for the (known) fracture corridor size distribution from seismic surveys and borehole image logs. The distribution also provides the fractional area of NFR occupied by the fracture corridors and exclusion (matrix) zone, which helps estimate the probability of on/off-fracture completion. In this study, we consider two (on-fracture/off-fracture) locations of well completion for conventional and DWS wells. When the location is certain (known) and fractures are densely distributed, placement of well’s completion has no effect on recovery performance. However, our results also show that in the fracture corridor network, single completed matrix wells are superior to fracture wells. Similarly, DWS wells dual-completed in a exclusion-zone would maximize the recovery. Probabilistic assessment of recovery is demonstrated for a field case NFR with known size distribution of fracture corridors. In case the reservoir is developed with single-completed wells the expected value of recovery factor is 33% with 42% and 58% of wells randomly completed in fracture corridor and exclusion-zone respectively. When DWS wells are used, probabilistic placement of two-completions is the same but oil recovery increases to 41%. The study demonstrates the need and a method for probabilistic assessment of recovery from bottom-water NFRs with sparsely-distributed fracture networks using conventional and dual-completed wells.
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Li, Jianing, Mahmoud Hamza, Arul Kumaran, Umesh Bhayaraju, and San-Mou Jeng. "Study of Development of a Novel Dual Phase Airblast Injector for Gas Turbine Combustor." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56340.
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A novel airblast injector is designed for gas turbine combustors. Unlike standard pressure swirl and prefilming/non-prefilming air blast atomizers, the novel injector is designed to improve the fuel injection delivery to the injector and improve atomization of the fuel by using a porous stainless steel tube. There are three swirling air streams in the injector. The liquid fuel is injected through the porous tube, with 7 micron porosity, between the swirling air streams, viz. an inner swirling air through the tube and the other two swirling air streams merging downstream of the tube. The swirl vane angles and the air split ratio are selected to increase the amount of air through the injector and facilitate the atomization process. The liquid fuel is injected through the outer surface of the porous tube, due to the permeability of the tube, produces a thin liquid sheet on the inner surface of the tube. The atomization occurs by surface stripping of the liquid sheet. The advantage of such an injector is that it produces a liquid sheet with uniform thickness around the circumference of the tube under all liquid loading. The porous tube also increases the surface area of contact between the fuel and air and produces a fine spray at engine idle conditions. An experimental approach is adopted in the present study to characterize the spray and aerodynamics of the injector for Jet-A and Gas-To-Liquid (GTL) fuels at atmospheric conditions. The effect of flare height on the Sauter Mean Diameter (SMD) is also studied. Spray characterization, droplet size and volume flux are investigated with PDI measurements. The effect of pressure drop and fuel properties on SMD distribution is analyzed. Velocity profiles at downstream of the injector are obtained from LDV measurements, and the velocity profile at the exit of the injector is also analyzed. A central toroidal recirculation zone (CTRZ) is observed at the exit of the injector. The effect of different configurations of the injector on spray characteristics is studied. A correlation for SMD is obtained.
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Evro, Solomon, Adnan Alshamali, Fahad AL-Faresi, Al-Qattan Mishari, Nejoud Al-Ostad, Galina Krasnova, Laila Hayat, et al. "Ervoir Simulation Evaluation of Cyclic Steam Stimulation Strategies in Tayarat Carbonate Heavy Oil Reservoir." In Middle East Oil, Gas and Geosciences Show. SPE, 2023. http://dx.doi.org/10.2118/213442-ms.
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Abstract The Tayarat formation extends over a large area; this formation has a diverse and complex geology and has heavy oil fluid system. A previous review of the analogous technologies that apply to the Tayarat heavy oil formation shows that it would be economically impossible to deploy a single reservoir development technology in all the areas of the field. In this project, we evaluated cyclic steam stimulation strategies focusing on applying different well completions. We have applied a compositional numerical simulation model using CMG Stars to investigate the application of different cyclic steam stimulation strategies. This includes using a traditional vertical well with a single steam injection point in the entire zone of the reservoir. We also investigated the use of vertical wells with dual string completion, where the short string injected into the upper parts of the formation while the long string injected into the lower part of the reservoir. With the horizontal well injection, we investigated open-hole completion and the case of using a horizontal well with multi-stage hydraulic fracturing. The potential of injecting steam at a higher rate with horizontal wells is attractive and requires more investigation. Apart from reducing the well count, we could overcome the surface constraints challenge in the field by stepping out of the congested areas and placing the horizontal section in the targeted part of the formation. With the advances in horizontal wells with multi-stage hydraulic fracturing in the industry, carbonate reservoirs such as Tayarat with low permeability could benefit from more reservoirs contact and possibly better steam distribution if we introduce adequate hydraulic fracture stimulation in the formation. The results of this study show that we could reduce our drilling footprint substantially by implementing a horizontal well with multi-stage hydraulic fracture stimulation in developing parts of the Tayarat carbonate heavy oil reservoir. Cyclic steam injection with vertical wells completed with dual strings shows a production advantage over a similar vertical well completed with a single string in similar zones. At the same time, horizontal wells with multi-stage hydraulic fracturing stimulation offer marginal benefits. The risk of increased hydraulic stimulation costs could undermine the value created by horizontal drilling and completion.
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Al-Sabea, Salem, Milan Patra, Abdullah Abu-Eida, Nasser Al-Azmi, Mohammad AlEidi, Mohamad Al-Dousari, Hasan Al-Qattan, et al. "A Cost-Effective Stimulation Workflow Unlocks New Perspectives for Matrix Acidizing in Openhole Horizontal Tight Carbonate – A Case Study from West Kuwait." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206133-ms.
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Abstract The Mishrif formation in west Kuwait is a tight carbonate reservoir having low oil mobility. It is fractured and heterogeneous with wide variation in porosity ranging from 10 to 25%, matrix permeability of about 0.1 to 10 md, and 20°API oil. Production tests and geomechanical study results have revealed that productivity is mostly from the high-permeability matrix and critically stressed fracture networks. Recently, the Mishrif development has been dominated by horizontal wells to maximize reservoir contact and enhance productivity. However, a challenge in such openhole completion is the stimulation strategy requiring effective diversion technology due to the uneven acid distribution along the lateral section. To address those challenges, a novel engineered workflow has been implemented relying on distributed temperature sensing (DTS) to assess the fluid coverage across the openhole section. Results enable identifying high- and low-intake zones, segmenting the uncased section into intervals requiring different levels of stimulation, and making informed decisions regarding diversion requirements. The intervention was conducted in two stages. Coiled tubing (CT) was the selected fluid conveyance method on the first stage given its capacity for more controlled fluid placement, and high-rate bullheading stimulation was selected for the second stage. During the treatment, multiple challenges were faced, mainly driven by a high-permeability streak identified by the DTS near the heel of the lateral. The CT stimulation procedures were modified on the spot, and measures were taken to minimize the impact on the thief zone, which included a combination of diversion techniques, such as high-pressure jetting, dual injection, and pumping of a near-wellbore nonreactive diverter, which is composed of a customized blend of multimodal particles and degradable fibers to minimize fluid leakoff into the high-intake zone. Likewise, real-time downhole telemetry was crucial throughout the CT stimulation because it allowed the highest injection rate possible below the preset pressure limits, continuous monitoring of downhole dynamics along the intervention, and optimal actuation of the high-pressure jetting tool. Upon completion of the CT stimulation, a second DTS log was carried out to evaluate the fluid coverage and effectiveness of the diversion strategy, enabling further adjustment of the bullhead stimulation program. This stimulation workflow implemented in west Kuwait represents a cost-effective alternative to stimulate openhole tight carbonates. This study brings new perspectives for treating complex reservoirs in the region, and shares lessons learned for future interventions.
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Franquet, Javier, A. N. Martin, Viraj Telaj, Hamad Khairy, Ahmed Soliman, Roman Zabirov, Syofyan Syofvas, et al. "Perfecting Straddle Packer Microfrac Stress Contrast Measurements for Hydraulic Fracturing Design in UAE Tight Oil Reservoir." In SPE Middle East Oil & Gas Show and Conference. SPE, 2021. http://dx.doi.org/10.2118/204700-ms.
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Abstract The objective of this work was to quantify the in-situ stress contrast between the reservoir and the surrounding dense carbonate layers above and below for accurate hydraulic fracturing propagation modelling and precise fracture containment prediction. The goal was to design an optimum reservoir stimulation treatment in a Lower Cretaceous tight oil reservoir without fracturing the lower dense zone and communicating the high-permeability reservoir below. This case study came from Abu Dhabi onshore where a vertical pilot hole was drilled to perform in-situ stress testing to design a horizontal multi-stage hydraulic fractured well in a 35-ft thick reservoir. The in-situ stress tests were obtained using a wireline straddle packer microfrac tool able to measure formation breakdown and fracture closure pressures in multiple zones across the dense and reservoir layers. Standard dual-packer micro-injection tests were conducted to measure stresses in reservoir layers while single-packer sleeve-frac tests were done to breakdown high-stress dense layers. The pressure versus time was monitored in real-time to make prompt geoscience decisions during the acquisition of the data. The formation breakdown and fracture closure pressures were utilized to calibrated minimum and maximum lateral tectonic strains for accurate in-situ stress profile. Then, the calibrated stress profile was used to simulate fracture propagation and containment for the subsequent reservoir stimulation design. A total 17 microfrac stress tests were completed in 13 testing points across the vertical pilot, 12 with dual-packer injection and 5 with single-packer sleeve fracturing inflation. The fracture closure results showed stronger stress contrast towards the lower dense zone (900 psi) in comparison with the upper dense zone (600 psi). These measurements enabled the oilfield operating company to place the lateral well in a lower section of the tight reservoir without the risk of fracturing out-of-zone. The novelty of this in-situ stress testing consisted of single packer inflations (sleeve frac) in an 8½-in hole in order to achieve higher differential pressures (7,000 psi) to breakdown the dense zones. The single packer breakdown permitted fracture propagation and reliable closure measurements with dual-packer injection at a lower differential reopening pressure (4,500 psi). Microfracturing the tight formation prior to fluid sampling produced clean oil samples with 80% reduction of pump out time in comparison to conventional straddle packer sampling operations. This was a breakthrough operational outcome in sampling this reservoir.
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Al-Yaqoubi, Mazin Marzouq, Hazim Hussain Abass, Hamyar Masaaod Al Riyami, Dalil Ainouche, Khalfan Mubarak Al Bahri, and Stephen Persac. "Hydraulic Fracturing a Reservoir in Proximity to a Water Zone – Oman Case History." In SPE Conference at Oman Petroleum & Energy Show. SPE, 2022. http://dx.doi.org/10.2118/200287-ms.
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Abstract Hydraulic fracturing is a challenge when the reservoir is adjacent to a water zone as it will extremely limit hydrocarbon production. The challenge becomes tougher when there is no stress barrier below the reservoir to contain the fracture. Several technologies have been applied by the oil and gas industry such as reducing injecting rate, using low viscosity, employing dual viscosity/density fracturing fluids, perforation location, and using proppant settling with dual fracturing treatment. The focus of this paper is to achieve two objectives; 1) place a long hydraulic fracture in the pay zone, and 2) avoid penetrating nearby water zone. This paper presents the proppant settling concept with essential augmentation that makes it a novel technology. The paper provides the oil and gas industry with a successful case history on fracturing low permeability reservoirs situated close to a water zone.
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Wang, Xiannan, Jian Wang, Lijun Guan, Bei Gao, Adriaan Gisolf, Zhaoya Fan, Ashers Partouche, et al. "Intelligent Wireline Formation Tester Evaluation of Low-Permeability and Low-Resistivity-Contrast Formation." In Offshore Technology Conference. OTC, 2023. http://dx.doi.org/10.4043/32269-ms.
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Abstract Exploration and development drilling in offshore China is extending to Paleogene formations that are characterized by low-resistivity-contrast and low-permeability rocks. These formations have become a focus for increasing reserves and production. During exploration activities, these low-resistivity, low-formation-contrast formations have been critical and challenging for formation evaluation because the geological structure and lithology are more complex than in previously discovered fields. Differentiating hydrocarbon from water using petrophysical interpretation has a large uncertainty in these formations. Confirming the fluid type using conventional formation testing technology has been extremely challenging because the produced fluid is mainly mud filtrate, which is no use for fluid confirmation. A new-generation intelligent wireline formation testing platform consisting of a focused radial probe inlet and a dual flowline with dual downhole pumps to enable flexible focused sampling was applied to three appraisal wells in offshore China. Given the larger flow area of the probe system, flow tests could be conducted in as low as 0.004-md/cP mobility zones (the tightest on record), and fluid identification could be performed in-situ while the fluid flowed through a group of sensors. Previous formation testing in these formations had been challenged because the water-based mud system caused suspension of solid particles (debris and mud solids). Filter and standoff accessories available with the intelligent wireline formation platform enabled designing a fit-for-purpose approach to overcome this challenge in a short time. This dedicated design resulted in increased efficiency in water sampling compared to previous testing done by the operator. Clean water resistivity, measured in situ, can now be applied to this new exploration block to recalculate the water saturation for reserve estimation. Whereas previous gas-water transition zone sampling was challenging because high water-based mud filtrate fractions masked the presence of formation water and formation hydrocarbon, the radial probe, combined with state-of-the-art resistivity measurements, allowed identification of gas and the measurement of formation water resistivity in a multiphase flow environment. The formation testing of these low-resistivity-contrast and low-permeability formations enabled acquisition of a 2% contaminated formation water sample in 140 minutes with formation mobility of 1 md/cP. The gas-water zone was confirmed from a dual flowline resistivity measurement and a hydrocarbon show in mobility of 1.4 md/cP.
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Butler, Benjamin, Justin Roberts, Matthew Kelsey, and Steffen Van Der Veen. "Mature Field Economic Rejuvenation with Infill and Re-Entry Multilateral Well Creation Techniques." In IADC/SPE Asia Pacific Drilling Technology Conference. SPE, 2021. http://dx.doi.org/10.2118/200996-ms.
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Abstract Multilateral wells have been proven over decades and have developed into a reliable and cost effective approach to mature field rejuvenation and extended commercial viability. This paper will discuss case studies demonstrating a number of techniques used to create infill multilateral wells in existing fields with a high level of reliability and repeatability. Techniques reviewed will cover cutting and pulling production casing to drill and case a new mainbore versus sidetracking and adding laterals to an existing mainbore. Discussion will also cover completion designs that tie new laterals into existing production casing providing significantly greater reservoir contact. Temporary isolation of high water-cut laterals brought into production later in the well's life through bespoke completion designs will also be discussed. Case studies will include discussion of workover operations, isolation methods, and lateral creation systems. Where available, resulting field performance improvements will also be discussed. In Norway, slot recoveries are commonly performed by cutting and pulling the 10-3/4" casing, redrilling a new mainbore, and running new casing. This enables junction placement closer to unswept zones and easier lateral drilling to targets. It does have drawbacks, however, related to the additional time required to pull the subsea xmas tree and challenges associated with pulling casing. In 2019, Norway successfully completed a 10-3/4" retrofit installation, whereas a sidetrack was made from the 10-3/4" and an 8-5/8" expandable liner was run down into the reservoir pay zone where two new laterals were created. The 8-5/8" liner saved time otherwise spent having to drill the section down to the payzone from the laterals. These wells have a TAML Level 5 isolated junction, Autonomous Inflow Control Devices (AICDs) in each lateral, and an intelligent completion interface across the junction, enabling active flow management and monitoring of both branches. In Asia, infill laterals were added to existing wellbores by sidetracking 9-5/8" casing and tying production back to the original mainbore. These dual laterals were completed with intelligent completions to enable lateral flow management and monitoring of both laterals. In Australia, dual laterals were created in a similar fashion; laterals are added to existing wells; however, a novel approach was used to manage water from existing lower mainbore laterals whereby they are shut in at completion and opened later when the new lateral is watered out. The older lateral now produces at lower water cut given the time allowed for water coning in the lateral to relax. Using this practice, production is alternated back and forth between the two laterals. In the Middle East, an older well has been converted from TAML Level 4 to Level 5 in order to prevent detected gas migrating into the mainbore at the junction. This conversion of a cemented junction well has enabled production to resume on this well. The well was converted to incorporate an intelligent completion to enable flow control of each lateral. This paper intends to provide insights into the various mature field re-entry methods for multilateral well construction, and a review of the current technology capabilities and well designs through the review of multiple case histories.