Day 2 Tue, June 12, 2018最新文献

{"title":"Impact of Composition on Natural Gas Desorption from Kerogen","authors":"W. Pang, S. Ding, Thongyi Zhang, Wenwu Xia, I. Akkutlu","doi":"10.2118/190762-MS","DOIUrl":"https://doi.org/10.2118/190762-MS","url":null,"abstract":"\u0000 Shale gas reservoirs hold adsorbed gas in kerogen. Laboratory techniques have been developed to measure the gas amount in samples. However, adsorbed gas recovery is an unsettled issue. Complexity is mainly due to adsorbed phase having an unknown composition and density, and desorbing in a selective fashion. Kerogen nanopores bring in added complexity to the analysis due to confinement effects. Our objective is to predict gas composition in kerogen pores and measure desorption limit during pressure depletion.\u0000 A new molecular simulation method is developed to predict in-situ composition of natural gas in model kerogen pores using composition of produced fluid from a Chinese shale gas well. In essence, the method re-distributes the fluid composition back into kerogen pores at initial reservoir conditions. Then one-by-one the pores are blown down in small pressure steps while the compositional variation in the pores is monitored. The recovery is measured by comparing the residual hydrocarbon molecules at different pressure steps during the blow down. Density, viscosity, mean free path of the fluids in model kerogen pores are computed using the trajectories of the adsorbed and free molecules.\u0000 At initial reservoir conditions we found that the gas mixture in kerogen nanopores becomes heavier and more viscous as the pore size becomes smaller. These compositional effects become significantly more amplified during the pressure depletion. Consequently, we observe that the kerogen pores release only the lighter end of the initial natural gas mixture in the pores, not allowing desorption of the heavier mixtures in smaller pores. The predicted Knudsen number values indicate that the compositional evolution in kerogen with pore size and pressure does not allow flow regime change. For the Chinese shale gas well fluid composition, we predict that the pores smaller than 5 nm has limited gas recovery and the transport in the larger pores stays in the slip flow regime.\u0000 The paper presents results of recovery from kerogen using molecular simulation of fluids in nanopores. The results bring in new insights into our understanding of the natural gas production limits from kerogen. The results indicate that methane adsorption isotherms do not represent the true nature of multi-component gas desorption from shale samples.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"282 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123456845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reconstruction of 3D Porous Media Using Multiple-Point Statistics Based on a 2D Training Image","authors":"Yuqi Wu, Chengyan Lin, L. Ren, Weichao Tian, Yang Wang, Yimin Zhang","doi":"10.2118/190859-MS","DOIUrl":"https://doi.org/10.2118/190859-MS","url":null,"abstract":"\u0000 Macroscopic transport properties of porous media essentially rely on the geometry and topology of their pore space. The premise of predicting these transport properties is to construct an accurate 3D pore space. To date the methods of modeling porous media are divided into two main groups, direct measurements by some equipment and stochastic statistical methods. Direct measurements of pore structure can be acquired with current equipment such as X-ray computed tomography and laser scanning confocal microscopy, but the unavailability of the equipment and the high cost of the measurement make their widespread application impossible. Many stochastic statistical methods, such as truncated Gaussian random field and simulated annealing methods, reconstruct 3D porous media based on some 2D thin sections by means of lower-order statistical functions. However these functions cannot reproduce the long-range connectivity of pore structure. Therefore, this paper will present a stochastic technique of reconstructing 3D pore space using multiple-point statistics with the purpose of solving the proposed problems. The single normal equation simulation algorithm (SNESIM), one of the most common methods for discrete variable simulation in multiple-point statistics, is the main tool to reproduce the long-range feature of pore space. To test the method, Berea sandstone was used as a sample. In the simulation process, a 2D thin section was taken as the training image for providing patterns of pore structure and some pixels were extracted from it as the conditioning data. The models were reconstructed using the SNESIM algorithm that serves as the simulation engine. In order to test the accuracy of these reconstructed models, pore geometry and topology and transport properties of the reconstructed models were compared with those of the real model obtained by X-ray computed tomography scanning. The comparison result shows that the reconstructed models are good agreement with the real model obtained by X-ray computed tomography scanning in the two-point correlation function, the pore space features and single- and two-phase flow permeabilities, which verifies that the long-range connectivity of pore space can be reproduced by this method. Comparing with other stochastic methods, a more accurate stochastic technique of reconstructing 3D porous media is put forward when only some 2D thin sections are available.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122103861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Hidden Threat of Irreversible Water Blockage in Low Porosity Gas Fields: Learnings from Pre-Production Paleo-Imbibition for Post-Production Field Management in Oman","authors":"M. Ferrero, I. Wahaibi, Mohamed Elshehabi, A. Farsi, Arlene Winchester, A. Aziz","doi":"10.2118/190780-MS","DOIUrl":"https://doi.org/10.2118/190780-MS","url":null,"abstract":"\u0000 The high residual gas trapping characteristics of low porosity rock are a considerable challenge for recovery of fields with bottom or edge water. Water lifting and handling is often a practical issue. Perforated intervals may suffer from permanent loss of gas mobility related to hysteresis effects due to imbibition of water (either production induced or paleo-residuals). The discrimination of \"trapped\" versus mobile gas intervals in a low porosity setting is not straight forward because data can be very deceiving: water imbibed zones may look alike free gas zones, but performance and recovery are quite different\u0000 This paper presents a show case of a clastic low porosity formation buried at 4Km depth. Following disappointing performance of the wells due to unexpected water production, the interpretation of pre-production fluid-fill-cycle revealed that a large percentage of the GIIP had been trapped over geological time due to tilting of the structure. Ignoring paleo-imbibition resulted in over-prediction of the recovery and misplacement of wells. Further imbibition of water into prolific zones during production of the field may result in early irreversible water loading of the wells with initial high rates.\u0000 A cross-discipline workflow has been put together to quantify field potential and water risk. A fit for purpose reservoir simulation with a focus on the fluid-fill-cycle can explain the performance of the wells to date and predict the expected recovery from paleo-residual volumes. Down flank co-production of gas and water has been proposed as mitigation for water blockage issues: 1st) to potentially delay further water cusping through prolific zones and 2nd) to enhance remobilization of gas trapped in the paleo-residuals zone.\u0000 The reported example illustrates the risks of water for gas recovery in low porosity formations, as learnt from a field with paleo-imbibition. We describe diagnostic tools for timely discrimination of paleo-trapped gas volumes to be considered prior to investment decisions, well placement and completions; we suggest fit for purpose models that can be constructed to represent rock and fluid physics without embarking into comprehensive full-field full-hysteresis models; we draw attention to specific permeability modeling guidelines for reservoirs containing significant volumes of low porosity rock to avoid overestimation of production plateau time. We recommend the planning of co-production of gas and water in flank wells to safeguard production from prolific zones in low porosity reservoirs with an aquifer.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"42 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131273328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimetal Study and Numerical Modelling of the Effect of Foaming Agent Properties on Foam Flooding in Porous Media in Absence of Oleic Phase","authors":"S. M. Hosseini-Nasab, M. Simjoo","doi":"10.2118/190779-MS","DOIUrl":"https://doi.org/10.2118/190779-MS","url":null,"abstract":"\u0000 This paper presents an investigation on the effect of foaming agents perpropeties in tetms of surfactant concentration, interfacial tension (IFT) and foam strength during foam flooding in porous media in the absence of oleic phase. The experiments consisted of the co-injection of gas and various surfactant solutions with three different formulation properties in terms of IFT reduction and foaming strength capability into Bentheimer sandstone samples initially saturated with the surfactant solution. Experiments were performed using Bentheimer sandstone cores during, where X-ray CT images were taken during foam generation to find out the stability of advancing front of foam propagation and to map the gas saturation for both the transient and steady-state flow regimes.\u0000 Then, a series of numerical simulation was conducted to investigate the effect of surfactant concentration on pressure drop across the core for the foam flooding in the absence of oil. The foam model implemented is based on a local equilibrium and describes dependency of foam mobility reduction factor using several independent functions, such as liquid saturation, foam velocity, oil saturation and capillary number. To this end, the dry-out and gas velocity functions in the foam model were determined from the experimental data obtained at low and high-quality regimes of foam flow at a constant injection velocity. Next, pressure drop profiles of foam flooding at two different surfactant concentrations were modelled to determine the parameters of the surfactant-dependent function in the foam model. The simulation results fit the experimental data of pressure drops very well.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"105 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122055354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"History Matching Using Hybrid Parameterisation and Optimisation Methods","authors":"Basil Al-shamma, O. Gosselin, P. King","doi":"10.2118/190776-MS","DOIUrl":"https://doi.org/10.2118/190776-MS","url":null,"abstract":"\u0000 Reservoir models are commonly used in the oil and gas industry to predict reservoir behaviour and forecast production in order to make important financial decision such as reserves estimations, infill well drilling, enhanced oil recovery schemes, etc. Conditioning reservoir models to dynamic production data is known as history matching, which is usually carried out in an attempt to enhance the predicted reservoir performance. Uncertainty quantification is also an important aspect of this task, and encompasses identifying multiple history matched models, which are constrained to a geological concept. History matching and uncertainty quantification can be accomplished by identifying and using efficient and speedy optimisation techniques. The assisted history matching practice usually includes two practices; the first of which is parameterisation, which consists of reducing the number of matching parameters in order to avoid adjusting too many variables with respect to the amount of production data available. A challenging situation results from over-parameterisation, in addition to an ill-posed formulation of the inverse problem. The second process involves optimisation, which aims at solving the inverse problem by reducing a misfit or objective function that defines the difference between simulated and production data. The main challenges of optimisation are local minima solutions and premature convergence. The success of optimisation is greatly dependent on the parameterisation strategy used. These algorithms that analyse various parameterisation methods, combined and examined with diverse optimisation algorithms lead us to suggest novel hybrid approaches addressing the two processes of assisted history matching. We propose a multistage combined parameterisation and optimisation history matching technique. Hybridisation of parameterisation and optimisation algorithms when designed in an optimum manner can combine advantageous features of each method. This consisted of combining random initial parameter population by means of a wide parameter search space optimiser at early stages with initial models chosen from the best history matched models of previous stages based on the initial parameter distribution with a fine tuning optimisation algorithm at later stages. The re-parameterisation at the beginning of each stage of a hybrid algorithm assists the process in escaping local minima and prevents premature convergence. The general design of these algorithms is to initialise with simple parameterisation methods and wide spread search algorithms, in which parameterisation zoning is increased and the parameter search space is reduce with time. These hybrid algorithms allow for consistent and effective parameter search space definition in which more than one minimum can be reached, further reduce the misfit after an initial convergence has been reached, improve efficiency by accelerating the optimisation process saving valuable computing time and con","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127129642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimization of Downhole Fluid Sampling Using Focused Probes","authors":"M. Kristensen, C. Machado, N. Chugunov","doi":"10.2118/190814-MS","DOIUrl":"https://doi.org/10.2118/190814-MS","url":null,"abstract":"\u0000 Acquisition of fluid samples using wireline formation testers is an integral part of reservoir evaluation and fluid characterization. The use of focused probe technology, in which the flow of mud filtrate to the main sampling port is shielded by one or more guard ports, has proved to be particularly effective in acquiring clean formation fluid samples with short pump-out times. To both improve operational efficiency for the current focused probes and optimize the design of next-generation tools, it is necessary to understand how to optimally operate the tools in different sampling environments. The objective of this study is to investigate optimal sampling strategies for focused tools in presence of formation and fluid property uncertainty. In particular, the pump rates for the sample and guard ports in a focused tool can be manipulated, allowing for optimization of pump rate profiles to maximize overall sampling efficiency.\u0000 We use a numerical forward model of the filtrate cleanup process coupled with optimization. We study the problem of pump rate profile optimization in different sampling environments and compare the results against two operating strategies commonly applied in the field.\u0000 The optimization results show that significant sampling time savings are possible (for each sampling station) compared with a default fixed-rate strategy, especially in environments characterized by a high viscosity contrast between the formation fluid and mud filtrate. These savings translate directly into rig time savings for the operator. In general, the results in the paper provide guidance on optimal focused-sampling operation in different environments.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129692356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical Modelling of Multiple Fractured Horizontal Wells in Shale gas Reservoirs","authors":"V. Bartoletti, C. Coll","doi":"10.2118/190851-MS","DOIUrl":"https://doi.org/10.2118/190851-MS","url":null,"abstract":"\u0000 One of today's challenges for shale reservoir developments is to increase the productivity per foot of drilled horizontal section while lowering the production cost to reduce the overall boe/$. Shale gas reservoirs are unconventional resources that need Multifractured Horizontal Wells (MFHW) to produce at commercial rates. Fracking methods have advanced dramatically in the last decade. Technologies are now capable of placing long MFHW with predefined fracs distance with large volumes of fluids injected causing intense formation fracturing. The final goal is to increase the well productivity per foot by increasing the size of the SRV (Stimulated Reservoir Volume) while reducing the cost of production.\u0000 The objective of this paper is to study and compare the impact on recovery factor, productivity and well performance of different SRV geometries using a dual porosity dual permeability compositional model. This work examines three prolific US gas shale plays, Haynesville, Barnett and Marcellus, having different reservoir and fluid characteristics. Hydraulic fractures properties like half-length, width and density were studied alongside other reservoir properties (matrix and fracture permeability and porosity). These are considered amongst the key parameters influencing MFHW productivity and gas recovery. The chosen approach is a Cartesian grid to mimic the presence of large-scale permeable hydraulic fractures as main flow conduits and enhanced medium scale (equivalent to the grid size) natural fractures in MFHW that contribute to flow in stimulated areas. The method models matrix-fracture interactions, with property-selected refinement to simulate different SRVs geometries demonstrated by Whitson (2016) to be able to history match pressure behavior in shale gas reservoirs for the Haynesville and Marcellus.\u0000 Numerical modeling of MFHW recovery factors, pressure and production profiles was done using a commercial simulator. Reservoir properties for analyzed shales were extracted from public data. Three different SRV models were studied to represent the enhanced medium scale fractures. The first model, matrix-hydraulic fractures system, is the simplest SRV modeled in this work, and is the base for a subsequent model obtained by adding an enhanced fracture stimulated SRV area around each large scale hydraulic fracture. The most complex SRV geometry modeled was created by adding an additional enhanced stimulated natural fracture area simulating the impact of hydraulic fractures in the medium scale natural fracture network (Whitson, 2016). Results show how relatively moderate increases in the enhanced stimulated SRV's volumes can have a large impact on cumulative gas production and recovery factor, demonstrating the importance of achieving successful large scale hydraulic fractures and/or stimulation of medium scale fractures between and around the major fractures. Changes in SRV geometry, caused by enhanced natural fractures due to hydraulic fracturing","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"053 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130926824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pore Shape Factors in Shale: Calculation and Impact Evaluation on Fluid Imbibition","authors":"Bin Yang, Lijun You, Yili Kang, Zhangxin Chen, Jian Yang, Han Huifen, Liang Wang","doi":"10.2118/190781-MS","DOIUrl":"https://doi.org/10.2118/190781-MS","url":null,"abstract":"\u0000 In shale gas reservoirs, the fluid imbibition was quite common during well drilling and stimulation, and it also related with engineering designs such as the borehole instability control and hydraulic fracturing operation, which fluid spontaneous imbibition into shales became a hot issues. In current fluid imbibition models, the pore shape was usually assumed to be circular tube, whereas scanning electron microscope (SEM) images analysis showed that the pore shapes in shale derived a lot from the ideal circular pores. One of the approaches to correct the deviation between the pore shapes and the ideal circular pores was to introduce a pore shape factor into the imbibition model. This paper provided a model to calculate the shape factors for specific geometric pores, and then based on the shape and proportion analyses of the inorganic and organic pores in shale, a comprehensive pore shape factor can be obtained. For tested two shale samples, the comprehensive pore shape factor was 0.54 and 0.61. Taking the values into the fluid imbibition model, it showed that the predicted curves accord quite well with the experimental data, and if the pore shape factors were ignored, there would present an overestimation of 37.0% and 27.9%, respectively. It seemed that calculating the pore shape factor accurately and involving it in the imbibition model would be very essential when dealing with the experimental fluid imbibition data or conducted field fluid imbibition volume predictions.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126240573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CO2 Sequestration Using Ensemble Kalman Filter and Considering a Sustainability Approach","authors":"R. Villegas, Clement Etienam, F. Rahma","doi":"10.2118/190803-MS","DOIUrl":"https://doi.org/10.2118/190803-MS","url":null,"abstract":"\u0000 CO2 Sequestration is one of the strategies currently used to decrease the amount of CO2 in the atmosphere. In this work, the modelling of CO2 sequestration involves the simulation of CO2 capture from flue gases and the CO2 storage in the subsurface considering a sustainability approach. The main focus of the CO2 sequestration is to reduce the greenhouse emission but in many cases, the models do not consider the carbon footprint associated with the process. We present an integrated approach where the CO2 sequestration model involves the power plant simulation of the CO2 capture, the numerical simulation of CO2 storage, economics and the life cycle assessment for the minimisation of the carbon footprint. This study provides an insight for future development of integrated approaches considering oxycombustion carbon capture focussed on the air separation unit and the simulation and monitoring of the subsurface storage sites.\u0000 Our work considers the CO2 capture process using Cryogenic and Membrane Air Separation Units for Oxi-Combustion because it is associated with a reduced carbon footprint when compared to other processes as post-combustion and pre-combustion. Our CO2 storage approach includes the compositional simulation of fluid flow in porous media and the characterisation of the sealing rock above realistic heterogeneous storage models by using an Ensemble Kalman Filter approach on a long term simulation of 100 years. Initial realisations of the subsurface model were generated using stochastic modelling and considering the uncertainty on the petrophysical properties of the rock, in particular permeability and porosity. In this work, one of the main purposes of the CO2storage simulation is to avoid the vertical leakage of the CO2 and for this, the fluid saturation in every cell is monitored during the simulation approach.\u0000 From the results associated with the oxy-combustion application, the Cryogenic model and membrane model reduce the carbon footprint by 78.34% and 66.84% respectively compared to the power plant model without carbon capture. It is also observed that electricity consumption produces the biggest carbon footprint portion for both models, hence future improvement should be focused in reducing process energy requirement. In terms of energy production, carbon footprint, and economic, oxy-combustion power plant with cryogenic air separation demonstrates better performance. However, the results of this study indicate that the membrane O2/N2 needs produce lower net power production and oxygen purity compared to the cryogenic model. Hence, further development of membrane material is still needed before it can be considered as a competitive option for air separation unit. An economic evaluation is also performed and the results show that cryogenic air separation is still a more economical option compared to membrane. The design of the well locations is dependent of the heterogeneity of the model and the correct characterisation of the s","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126660819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on the Coupled Effect of Effective Stress and Methane Gas Adsorption on the Porosity and Permeability of Shale Gas Reservoirs","authors":"W. Tian, Huiqing Liu, S. He, Jing Wang, Zequan Zhang, M. Zheng, Z. Ning","doi":"10.2118/190875-MS","DOIUrl":"https://doi.org/10.2118/190875-MS","url":null,"abstract":"\u0000 Shale gas is considered very important unconventional hydrocarbon resources. Due to the technological advances of hydraulic fracturing, the development of shale gas has become the main focus in recent years. Porosity and permeability are the most important petrophysical parameters during the production of shale gas. A considerable amount of research work has been carried out on stress law of porosity and permeability. However, nearly none of them considered the effects of methane adsorption.\u0000 This paper utilizes the simplified local-density (SLD) theory to study adsorption of supercritical gas in shale gas reservoirs. On the basis of the basic features of high pressure supercritical adsorption of shale gas, Peng—Robinson equation is used to describe adsorbed fluid. The interaction between the gas molecules and porewalls of shale is considered using Lennard-Jones potential. Finally, we establish the SLD model to do regression analysis for the adsorption experiments data. The density of adsorbed phase and free phase density could be obtained applying SLD model and then the amount of gas adsorption can be determined. The Gibbs adsorption amount calculated using the SLD model is used to establish matrix strain model. Finally, the strain model is incorporated into widely used analytical porosity and permeability models to develop the coupled model with consideration of the coupled effect of gas adsorption and stress on the porosity and permeability of shale gas reservoirs. And the trend of variation of porosity and permeability of shale rocks taking account of the effects of stress and gas adsorption can be obtained.\u0000 Lab experiments of gas adsorption of methane gas are made on three shale samples. The developed SLD model is applied to describe gas adsorption data. The outcome indicates that SLD model can properly analyze and fit the experimental data. From the results calculated by the new developed model of porosity and permeability, we can conclude that porosity ratios and permeability ratios of gas shales decrease with the increase of pore pressure, which is contrary to the tendency of changes in porosity and permeability only taking account of the effects of effective stress. This result demonstrates that gas adsorption has very large impact on pore volume, therefore the deformation of matrix induced by the adsorption of methane gas cannot be neglected.\u0000 The proposed model could further be used for the accurate evaluation of storage capacity of shale gas reservoirs and gas production of wells.","PeriodicalId":339784,"journal":{"name":"Day 2 Tue, June 12, 2018","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114467633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}