The Experts below are selected from a list of 5877 Experts worldwide ranked by ideXlab platform
Ruizhong Jiang - One of the best experts on this subject based on the ideXlab platform.
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The numerical simulation of thermal recovery considering rock deformation in shale gas reservoir
International Journal of Heat and Mass Transfer, 2019Co-Authors: Jianwei Yuan, Ruizhong Jiang, Yongzheng Cui, Qiong Wang, Wei ZhangAbstract:Abstract Recently, shale gas is a hot spot of research as an unconventional resource. Advances in horizontal well drilling technology and fracturing technology have contributed to increased shale gas recovery. Different from conventional gas reservoirs, the adsorption gas content is as high as 85%, so the amount of adsorbed gas liberated from the matrix surface is very helpful for ultimately improving the recovery of shale gas. Recently, some progress has been made in the process of hydraulic fracture heating technology. The event that temperature variation promotes the release of adsorbed gas and thus enhances oil recovery has not been fully studied. In addition, during shale gas production, stress sensitivity, adsorption desorption and temperature will all have a significant effect on rock deformation, which will change the permeability of the matrix and fractures. To study the effect of thermal recovery based on coupled geomechanical effects and fluid flow. A numerical model of shale gas thermal recovery considering Knudsen diffusion, adsorption desorption and stress sensitivity was established to reflect the production process of shale gas. Moreover, discrete fracture is employed to describe hydraulic fractures and natural fractures. The influence of thermal expansion on rock deformation is considered in the geomechanical effect, and the permeability formula suitable for shale gas thermal recovery is developed. Finally, the effects of different parameters on thermal recovery were studied separately. It is obvious that heating hydraulic fractures improves the recovery of shale gas by promoting the liberate of adsorbed gas. A large amount of adsorbed gas is produced as the stimulation temperature increases. Considering the stress-sensitive permeability can more accurately reflect the change of permeability in the shale gas thermal recovery process, so as to more accurately predict the production of shale gas. The increase in recovery rate of shale gas thermal recovery depends on the stimulation temperature, bottom hole pressure, matrix heat capacity, thermal conductivity, Langmuir Volume and matrix permeability. The larger the Langmuir Volume and the higher the bottom hole pressure, the better the thermal recovery effect for improving shale gas recovery.
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Production forecast of fractured shale gas reservoir considering multi-scale gas flow
Journal of Petroleum Exploration and Production Technology, 2016Co-Authors: Wei Zhang, Jianchun Xu, Ruizhong JiangAbstract:The shale gas experiences many different spatial scales during its flow in the reservoir, which will engender different flow mechanisms. In order to accurately simulate the production performance of shale gas well, it is essential to establish a multi-continuum model for shale gas reservoir. Based on the geometrical scenario of multistage horizontal well fracturing, this paper builds up a triple-continuum model incorporating three systems: matrix with extremely low permeability, less permeable natural fractures and highly permeable hydraulic fractures. This numerical model employs Langmuir adsorption equation to present the influence of desorption gas in matrix and considers the Klinkenberg effect in matrix and natural fractures by adjusting the apparent permeability. The solution of this model is achieved using implicit scheme. Eventually, this model is applied on the single well production situation in a synthetic reservoir, production decline curves and cumulative production curves are obtained, then the sensitivity analysis is made on various kinds of parameters; thus, the influences of these parameters on production rate are obtained: The gas rate will rise with the increase in hydraulic fracture half-length, meshing size, Langmuir Volume and Langmuir pressure, but with the decrease in hydraulic fracture spacing.
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Production performance analysis of multiple fractured horizontal wells with finite-conductivity fractures in shale gas reservoirs
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Wenchao Teng, Ruizhong Jiang, Lin Teng, Xin Qiao, Yu Jiang, Yihua GaoAbstract:Abstract Shale gas flow is controlled by multiple mechanisms and multi-stage hydraulic fracturing often creates complex fracture geometry. It is very challenging to incorporate various transport mechanisms of shale gas and evaluate production performance of the multiple fractured horizontal well (MFHW) in shale gas reservoirs. This paper presented a new semi-analytical model to study the pressure behavior and production performance of MFHWs with finite conductivity fractures in shale gas reservoirs. Multiple mechanisms were considered, which contained diffusion in kerogen bulk, desorption from the surface of organic matters and clay minerals, slippage flow in matrix pores, transient-state inter-porosity flow and Darcy flow in natural fractures. Finite-conductivity hydraulic fractures, stress sensitivity effect and inclination angles were also taken into account. Line source function, Laplace transformation, perturbation technique, numerical discrete method, Gauss elimination method and Stehfest inversion algorithm were employed to calculate the pressure responses. A field case from Barnett Shale was used to illustrate the validity of this model. Type curves were plotted and flow regimes were identified. A synthetic case was used to study the effects of hydraulic fracture conductivity, inclination angle, permeability modulus, kerogen content, clay minerals content, solubility coefficient, diffusion coefficient, Langmuir pressure and Langmuir Volume on well production performance. By performing sensitivity analysis of key factors, we come to some conclusions that hydraulic fracture conductivity has an optimal value for shale gas development; a small inclination angle and a large permeability modulus have a negative effect on well performance while a large Langmuir pressure and Langmuir Volume have a positive effect; both clay minerals and organic matters contribute to shale gas production; dissolved gas stored in kerogen bulk should be considered and a larger diffusion coefficient is beneficial for dissolved gas to release. With its rapid computational speed, this semi-analytical approach will serve as an efficient tool to evaluate well productivity and provide critical insights into development optimization of shale gas reservoirs.
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Production performance analysis for composite shale gas reservoir considering multiple transport mechanisms
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Chaohua Guo, Mingzhen Wei, Ruizhong JiangAbstract:Abstract To better evaluate production performance of shale gas reservoir development, it is urgent to resolve the Stimulated Reservoir Volume (SRV) enigma. However, it is very challenging to characterize the SRV considering multiple transport mechanisms. The SRV is always very complex after fracturing and refracturing. Hence, it is paramount to develop new models to describe SRV and analyze the well performance for shale gas reservoirs. In the paper, we present a dual-region composite reservoir model for multistage fractured horizontal well when developing shale gas. In this model, multiple transport mechanisms were considered including desorption, diffusion, and viscous flow. Then, the model solution and its validation against other semi-analytical model results were presented. Different flow regimes were divided according to pressure transient analysis curves. Sensitivity studies to quantify the key parameters affecting the well performance were performed finally. Seven variables, which are Langmuir Volume, Langmuir pressure, diffusion coefficient, inner region radius, inner region permeability, stress sensitivity coefficient, and hydraulic fracture conductivity, were investigated. The model proposed here is more comprehensive by considering not only SRV but also the transport mechanisms of shale gas, and can be used for performance analysis in shale gas reservoir development.
Huijie Bi - One of the best experts on this subject based on the ideXlab platform.
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A fully coupled thermal-hydraulic-mechanical model with two-phase flow for coalbed methane extraction
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Sheng Li, Zhenhua Yang, Huijie BiAbstract:Abstract Although the interaction of gas and coal has been comprehensively investigated in coalbed methane (CBM) extraction process, fewer scholars have taken the effect of temperature and groundwater into account, which brought a large deviation for CBM extraction design. In this study, a fully coupled thermal–hydraulic–mechanical model (THM) including coal deformation, gas seepage, water seepage, and thermal transport governing equations is developed and solved using the finite element (FE) method. The coal mass is simplified as a dual-porosity and single-permeability media while CBM migration is considered as a tandem process of desorption, diffusion and seepage. The dynamic evolution model of permeability serving as the coupled term for THM model is developed under the combined impact of stress, water pressure, gas pressure, gas adsorption/desorption and temperature. The proposed model is first verified by showing that the modeled gas production rate and water production rate match reasonably with the in-situ measured ones. Different coupled models for CBM extraction were comparatively analyzed by accomplishing a series of simulations. It is found that the gas production rate of models ignored water effect monotonously reduces over time; while the model considered water effect rises at beginning and then gradually reduces. The model ignored water effect will overestimate gas production, and the model ignored thermal effect will underestimate gas production, particularly coal seam contains considerable amount of water. The evolution of permeability is the competition result of two opposite effects: the matrix shrinkage effect caused by temperature reduction, the matrix swelling effect caused by gas pressure decrease and methane adsorption increase. A rising permeability resulted from the integrative action of both lower reservoir temperature and pressure during CBM extraction is observed. The impact of initial water saturation on gas production can not be ignored in the whole extraction process, especially during the water drainage period. Gas production rate of CBM well decreases with initial reservoir temperature, initial water saturation and Langmuir Volume constant, while increases with the Klinkenberg factor. Permeability rate increases with initial water saturation and Klinkenberg factor, however decreases with initial reservoir temperature. As Langmuir Volume constant increases, the peaking value of gas production rate increases and delays. The Klinkenberg effect promotes coalbed methane migration significantly, ignoring which will underestimate the gas production, and the impact of Klinkenberg effect gradually increases with the drop of gas pressure.
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A fully coupled thermal-hydraulic-mechanical model with two-phase flow for coalbed methane extraction
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Sheng Li, Zhenhua Yang, Huijie BiAbstract:Abstract Although the interaction of gas and coal has been comprehensively investigated in coalbed methane (CBM) extraction process, fewer scholars have taken the effect of temperature and groundwater into account, which brought a large deviation for CBM extraction design. In this study, a fully coupled thermal–hydraulic–mechanical model (THM) including coal deformation, gas seepage, water seepage, and thermal transport governing equations is developed and solved using the finite element (FE) method. The coal mass is simplified as a dual-porosity and single-permeability media while CBM migration is considered as a tandem process of desorption, diffusion and seepage. The dynamic evolution model of permeability serving as the coupled term for THM model is developed under the combined impact of stress, water pressure, gas pressure, gas adsorption/desorption and temperature. The proposed model is first verified by showing that the modeled gas production rate and water production rate match reasonably with the in-situ measured ones. Different coupled models for CBM extraction were comparatively analyzed by accomplishing a series of simulations. It is found that the gas production rate of models ignored water effect monotonously reduces over time; while the model considered water effect rises at beginning and then gradually reduces. The model ignored water effect will overestimate gas production, and the model ignored thermal effect will underestimate gas production, particularly coal seam contains considerable amount of water. The evolution of permeability is the competition result of two opposite effects: the matrix shrinkage effect caused by temperature reduction, the matrix swelling effect caused by gas pressure decrease and methane adsorption increase. A rising permeability resulted from the integrative action of both lower reservoir temperature and pressure during CBM extraction is observed. The impact of initial water saturation on gas production can not be ignored in the whole extraction process, especially during the water drainage period. Gas production rate of CBM well decreases with initial reservoir temperature, initial water saturation and Langmuir Volume constant, while increases with the Klinkenberg factor. Permeability rate increases with initial water saturation and Klinkenberg factor, however decreases with initial reservoir temperature. As Langmuir Volume constant increases, the peaking value of gas production rate increases and delays. The Klinkenberg effect promotes coalbed methane migration significantly, ignoring which will underestimate the gas production, and the impact of Klinkenberg effect gradually increases with the drop of gas pressure.
Deliang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Research on transient flow theory of a multiple fractured horizontal well in a composite shale gas reservoir based on the finite-element method
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Rui-han Zhang, Yulong Zhao, Liehui Zhang, Rui-he Wang, Deliang ZhangAbstract:Abstract A shale gas reservoir, as a special type of gas reservoir, is significantly different from a conventional gas reservoir. Gas flow in shale involves a complex process of multiple flow mechanisms (including adsorption, diffusion, slippage, and viscous flow in multi-scaled systems of nano-to macro-porosity) that substantially deviates from Darcy flow. The multiple hydraulic fracturing procedure not only creates the stimulated reservoir Volume (SRV) to improve production but also causes the flow in the shale to become more complex. In this work, we first propose a dual porosity continuum and discrete fracture model to describe the flow of MFH well in a rectangular composite shale gas reservoir. The finite element method based on the unstructured 3D tetrahedral meshes is used to obtain a numerical solution. Next, we assume a transient well index to correct the early calculation error caused by the mesh precision and obtain the complete pressure transient and production decline curves. Sensitivity analyses show that the Langmuir Volume, equivalent apparent permeability, hydraulic fracture distribution and size of SRV have great impacts on the transition flow regime and production performance. The research results obtained in this paper can provide theoretical guidance for efficient and large-scale development of shale gas reservoirs.
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A composite model to analyze the decline performance of a multiple fractured horizontal well in shale reservoirs
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Deliang Zhang, Yulong Zhao, Liehui Zhang, Jingjing GuoAbstract:Abstract In this work, we present a composite model that considers the effect of gas desorption to describe the fluid flow performance of a hydraulic multistage fractured horizontal (MFH) well with stimulated reservoir Volume (SRV) in shale. Based on the Langmuir adsorption isotherm, Fick's law and dual-porosity idealization, this MFH well model for shale gas reservoirs is tailored to our problem conditions and solved using discrete numerical methods. Then, Stehfest's numerical algorithm and the Gauss elimination method are used to obtain production decline and pressure transient type curves. The main flow regimes of shale gas MFH wells are identified with the following characteristics: wellbore storage, linear flow in the SRV region, diffusion flow and later pseudo-radial flow periods. Sensitivity analyses show that the transition flow regime and the production performance of an MFH well in shale are mainly affected by the Langmuir Volume, radius and permeability of the SRV region. This study provides some insights into the mechanisms of shale gas flow and assists in understanding the production decline dynamics in shale reservoirs.
Kai Yao - One of the best experts on this subject based on the ideXlab platform.
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Numerical evaluation on multiphase flow and heat transfer during thermal stimulation enhanced shale gas recovery
Applied Thermal Engineering, 2020Co-Authors: Jia Liu, Xin Liang, Yi Xue, Kai YaoAbstract:Abstract A fully coupled thermo-hydro-mechanical model in multiphase shale gas reservoirs is first developed and is then validated with analytical solutions and experimental result. Subsequently, the coupling responses are investigated to addressing mechanisms of gas recovery enhancement. Finally, a series of parameter sensitivity analyses are implemented to investigate the effect of parameters on gas recovery. The results indicate that gas production is strongly dependent on heating temperature, while the economic benefits should be evaluated further. The heating treatment for shale gas reservoirs not only rapidly desorbs the adsorbed gas, but also quickly evaporates the water in the pores within the shale, which removes the water lock effect and makes the desorbed gas produced smoothly. The parameters such as permeability, thermal conductivity, bottom-hole pressure, Langmuir Volume, and entry capillary pressure also affect thermal recovery, which should be considered comprehensively to evaluate thermal recovery efficiency. Hydraulic fracturing enhances gas recovery at early-stage, and formation heat treatment can promote gas source supply at later-stage. Therefore, the combination of the two techniques can extend the life of shale gas wells and achieve effective and sustainable development of shale gas.
Liang Wang - One of the best experts on this subject based on the ideXlab platform.
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intrinsic relationship between Langmuir sorption Volume and pressure for coal experimental and thermodynamic modeling study
Fuel, 2019Co-Authors: Yun Yang, Shimin Liu, Wei Zhao, Liang WangAbstract:Abstract Gas adsorption Volume has long been recognized as an important parameter for coalbed methane (CBM) resource assessment as it determines the overall gas capacity of coal. As the industrial standard practice, Langmuir Volume (VL) is used to describe the gas adsorption Volume. Another important parameter, Langmuir pressure (PL), is typically overlooked because it does not directly relate to the resource estimation. However, PL defines the slope of the adsorption isotherm and the ability of a well to attain the critical desorption pressure in a significant reservoir Volume, which is critical to plan the initial water depletion rate for a CBM well. Qualitatively, both VL and PL are related to the fractal pore structure of coal, but the intrinsic relationships among fractal pore structure, VL, and PL are not well studied and quantified due to the complex pore structure of coal. In this study, a series of experiments were conducted to measure the fractal dimensions of coal and their relationship to methane adsorption capacity. The thermodynamic model of the gas adsorption on heterogonous surfaces was revisited, and the theoretical models that correlate the fractal dimensions with the Langmuir constants were proposed. Applying the fractal theory, adsorption capacity ( V L ) is proportional to a power function of specific surface area and fractal dimension, and the slope of the regression line contains information on the molecular size of the adsorbed gas. We also found that P L is linearly correlated with sorption capacity, which is defined as a power function of total adsorption capacity ( V L ) and a heterogeneity factor (ν). This implies that PL is not independent of VL, instead, a positive correlation between V L and P L has been noted elsewhere (e.g., Pashin [1]). In the Black Warrior Basin, Langmuir Volume is positively related to coal rank (Pashin, 2010; Kim, 1977) [1,2], and Langmuir pressure is inversely related to coal rank. It was also found that P L is negatively correlated with adsorption capacity and fractal dimension. A complex surface corresponds to a more energetic system, which results in an increase in the number of available adsorption sites and adsorption potential, which raises the value of V L and reduces the value of P L .
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Pore structure and its impact on CH4 adsorption capability and diffusion characteristics of normal and deformed coals from Qinshui Basin
International Journal of Oil Gas and Coal Technology, 2015Co-Authors: Yuanping Cheng, Liang WangAbstract:In this study, the pore structure, adsorption/desorption kinetics and thermodynamics of normal and deformed coals are compared. The total pore Volume and porosity of deformed coal are 2.84 to 2.91 times greater than those of normal coal, whereas the micropore Volume and specific surface area of normal coal are 1.15 to 1.35 times greater than those of deformed coal. Langmuir Volume of normal coal is greater than that of deformed coal. Δσ of normal coal is slightly greater than that of deformed coal which indicates that the unit area of normal coal CH4 adsorption capacity is also greater than that of deformed coal. At the early stage of the desorption process, the mass diffusivity of deformed coal is ten times greater than that of normal coal. Then it decreases rapidly, while that of normal coal decreases very slowly. At last, it will be less than that of normal coal. [Received: January 5, 2013; Accepted: April 30, 2013]
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The effect of small micropores on methane adsorption of coals from Northern China
Adsorption, 2012Co-Authors: Yuanping Cheng, Liang WangAbstract:In this study, the effect of coal micropores on the adsorption properties, especially the Langmuir pressure (P L ), was investigated by testing 11 coal samples from Northern China. The adsorption of CO2 at 273 K was utilized to analyze the pore size distribution. The results of these coals show that micropore Volume and micropore surface area are the major factors affecting the Langmuir Volume (V L ) but have weaker effects on P L . Micropore filling theory considers that some smaller micropores with an obvious overlapping adsorption force cause Volume filling adsorption. These micropores firstly reach saturated adsorption, controlling the adsorption Volume at the low-pressure stage and thus have a great effect on P L . Four times the methane molecular diameter, 1.5 nm, was assumed as the critical pore size with obvious overlapping adsorption force. The relationship between P L and the proportion of the pore Volume below 1.5 nm to the micropore Volume was investigated, and it was found that the higher the Volume proportion of these small micropores was, the smaller the P L was, though two data points deviated from this trend. The reason for the anomalous coal samples could be the deviation from the assumed critical pore size of 1.5 nm for Volume filling and the effects of the various micropore surface properties, which await further study.
