The Experts below are selected from a list of 21222 Experts worldwide ranked by ideXlab platform
Hongqing Song - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of low velocity non Darcy Flow of gas and water in coal seams
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Gang Huang, Hongqing Song, Jiaosheng Yang, Yuhe Wang, John KilloughAbstract:Abstract Fluid Flow in low-permeability coal seams shows characteristics of low-velocity non-Darcy Flow. A two-phase mathematical Flow model considering the effect of the threshold pressure gradient (TPG) for gas and water transportation and Flow in such reservoirs has been developed. The corresponding numerical model has been formulated and solved. From the numerical results, we can conclude that both the gas production rate and cumulative gas production in the case when TPG is considered are always less than those in the cases when TPG is not considered because of the sharply decreased pressure and increased energy consumption. A comparison of the gas production rates obtained from the calculation results and from monitoring data indicates that the gas production rate predicted using the model with TPG is more accurate. Under the calculation conditions, the gas production rates when considering different values of TPG are approximately 35%–70% less than those for cases without TPG. In addition, the gas production rate and total gas production decrease as the bottom hole pressure and TPG increase, but they increase with the fracture half length. However, these factors have little influence on the water production regardless of the incorporation of TPG. The research expands the theoretical basis of gas recovery from the tight coal seams and provides a more accurate method to predict the gas production rate efficiently.
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numerical research on co2 storage efficiency in saline aquifer with low velocity non Darcy Flow
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Zhiyong Song, Hongqing Song, John Killough, Juliana Y Leung, Gang HuangAbstract:Low permeability saline aquifers, which are widely distributed around this world, have great potential for injected CO2 storage. Fluid Flow in low permeability layers shows characteristics of low-velocity non- Darcy Flow. A mathematical model considering the effect of threshold pressure gradient (TPG) for CO2 Flow and storage in low permeability saline aquifer has been developed, and the corresponding nu- merical model has been formulated and solved. From the numerical results, we can conclude that the injection rate, cumulative CO2 injected, and the storage efficiency for the case with TPG are always less than those of the case without TPG because of the sharp pressure decline and increased energy con- sumption. Under this paper's calculation condition, the storage efficiency when considering TPG is about 10% less than the case without considering TPG. If the TPG effect was to be ignored in the design of CO2 storage in low permeability saline aquifers, the CO2 storage efficiency will be overestimated. The research enlarges the theoretical basis of carbon capture and storage (CCS) and provides a more accurate method to evaluate CO2 storage efficiency. © 2015 Published by Elsevier B.V.
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productivity equation of fractured horizontal well in a water bearing tight gas reservoir with low velocity non Darcy Flow
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Hongqing Song, Dawei Yang, Mingxu YuAbstract:Abstract Based on the features of tight gas reservoirs and considering the existence of threshold pressure gradient (TPG), a new mathematical model was established for low-velocity non-Darcy Flow in water-bearing tight gas reservoirs. Calculation method of control areas is also presented. Productivity equations of vertical fractured well and horizontal fractured well in tight gas reservoirs are obtained with TPG. Influential factors were analyzed to provide theoretical basis for the effective development of tight gas reservoirs. According to the numerical results, with the increase of pressure drawdown, both the volumetric Flow rate of gas well and control area grow first and then gradually becomes stable. The influence of TPG on the volumetric Flow rate of gas well is great and cannot be neglected. For fractured horizontal well, gas well production increases with the increase of Flow conductivity capacity and half-length of hydraulic fractures. For certain length of the borehole, when the fracture spacing increases and the number of the fractures decreases, the control area and the volume Flow rate of the gas well decreases. Consequently, there is an optimum allocation among drawdown pressure, fracture half-length, fracture conductivity and fracture spacing to achieve maximum production.
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formation pressure analysis of water bearing tight gas reservoirs with unsteady low velocity non Darcy Flow
Advanced Materials Research, 2011Co-Authors: Hongqing Song, Dong Bo He, Huai Jian YiAbstract:Porous media containing water is the prerequisite of existence of threshold pressure gradient (TPG) for gas Flow. Based on theory of fluid mechanics in porous medium considering TPG, the non-Darcy Flow mathematical model is established for formation pressure analysis of water-bearing tight gas reservoirs. It could provide semi-analytic solution of unsteady radial non-Darcy Flow. According to the solution of unsteady radial non-Darcy Flow, an easy and accurate calculation method for formation pressure analysis is presented. It can provide theoretical foundation for development design of water-bearing tight gas reservoirs. The analysis of calculation results demonstrates that the higher TPG is, the smaller formation pressure of water-bearing tight gas reservoirs spreads. In the same output, the reservoir sweep of non-Darcy gas Flow is larger than that of non-Darcy liquid Flow. And the pressure drop near wellbore is smaller than that of non-Darcy liquid Flow, which is different from Darcy Flow.
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A Study of Effective Deployment in Ultra-Low-Permeability Reservoirs With Non-Darcy Flow
Petroleum Science and Technology, 2010Co-Authors: Hongqing Song, Weiyao Zhu, M. Wang, Y. K. Sun, Xiao ChenAbstract:Abstract Due to the existence of a threshold pressure gradient (TPG) in ultra-low-permeability reservoirs, the peripheral reserves of the wellbore are difficult to deploy effectively. The main problem is that it is hard to ensure that well pattern, well spacing, and drawdown pressure easily and accurately because of the existence of low-velocity non-Darcy Flow in such reservoirs. Simple and accurate calculation methods of the problem are most popular with reservoir engineers, so effective deployment calculation methods of ultra-low-permeability reservoirs are presented in this article. They include control radius calculation, control distance calculation, control area calculation, and control coefficient calculation, which can be directly used in the evaluation of well pattern thickening of developed oilfields and reserves of undeveloped oilfields. Based on theory of fluid mechanics in porous medium considering TPG, the non-Darcy Flow mathematic model was established to reveal the characteristics of press...
Mingxu Yu - One of the best experts on this subject based on the ideXlab platform.
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productivity equation of fractured horizontal well in a water bearing tight gas reservoir with low velocity non Darcy Flow
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Hongqing Song, Dawei Yang, Mingxu YuAbstract:Abstract Based on the features of tight gas reservoirs and considering the existence of threshold pressure gradient (TPG), a new mathematical model was established for low-velocity non-Darcy Flow in water-bearing tight gas reservoirs. Calculation method of control areas is also presented. Productivity equations of vertical fractured well and horizontal fractured well in tight gas reservoirs are obtained with TPG. Influential factors were analyzed to provide theoretical basis for the effective development of tight gas reservoirs. According to the numerical results, with the increase of pressure drawdown, both the volumetric Flow rate of gas well and control area grow first and then gradually becomes stable. The influence of TPG on the volumetric Flow rate of gas well is great and cannot be neglected. For fractured horizontal well, gas well production increases with the increase of Flow conductivity capacity and half-length of hydraulic fractures. For certain length of the borehole, when the fracture spacing increases and the number of the fractures decreases, the control area and the volume Flow rate of the gas well decreases. Consequently, there is an optimum allocation among drawdown pressure, fracture half-length, fracture conductivity and fracture spacing to achieve maximum production.
Jian-guo Wang - One of the best experts on this subject based on the ideXlab platform.
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combined effects of directional compaction non Darcy Flow and anisotropic swelling on coal seam gas extraction
International Journal of Coal Geology, 2013Co-Authors: Jishan Liu, Jian-guo Wang, A. KabirAbstract:Abstract The effects of directional compaction, non-Darcy Flow and anisotropic swelling on the extraction of natural gas in coal seam reservoirs are important but not well understood so far. This paper investigated these combined effects through a numerical model which fully couples the interactions of coal seam deformation, anisotropic gas Flow in fractures, and anisotropic absorption/adsorption of natural gas in coal matrix. In the sorption process, the Langmuir isotherm is extended by including some microstructure information to describe sorption induced anisotropic swelling strain (called anisotropic swelling). The Forchheimer equation is reformulated to consider the non-Darcy effect in directional Flows (called non-Darcy Flow). A strain ratio of matrix to fractured element is introduced for the directional compaction induced evolution of permeability (called directional compaction). The effect of anisotropic swelling strain is also converted into anisotropic swelling body forces in the mechanical deformation process. This model is verified by the experimental results of single fracture Flow under compaction. This verified model is used to quantify the relative importance of directional compaction and matrix swelling through a block model containing a single fracture. It is found that directional compaction of the single fracture can reduce the permeability by 70% and matrix swelling can reduce the permeability by over 30%. This example illustrates the important contribution of matrix swelling to the anisotropy of permeability. This fully-coupled model is applied to a production well in a coal seam gas reservoir to investigate the combined effects of directional compaction, non-Darcy Flow and anisotropic swelling on well production rates. It is found that both directional compaction and anisotropic swelling can significantly induce the anisotropy of permeability, forming a skin damaged zone and largely affecting the production rate of natural gas extraction. Directional compaction and anisotropic swelling can significantly accentuate the non-Darcy effect near wellbore for unconventional coal seam gas reservoirs. Thus, the anisotropic evolution of permeability near wellbore cannot be ignorable for the evaluation of production data.
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Effects of non-Darcy Flow on the performance of coal seam gas wells
International Journal of Coal Geology, 2012Co-Authors: Jian-guo Wang, Jishan Liu, A. Kabir, Zhongwei ChenAbstract:Although it has been reported that the gas Flow in the cleat system may be of the non-Darcy nature, little has been known on how this non-Darcy Flow affects the coal seam gas (CSG) extraction. One of the major reasons is that prior studies on this subject have not included the impact of gas sorption-induced coal deformation (swelling or shrinking) and the nature of two extremely different time scales between processes in the coal matrix and ones in the cleat system. In this study, a fully coupled finite element (FE) model of coal deformation (gas sorption induced swelling or shrinking), non-Darcy Flow in fractures and gas diffusion in coal matrix is developed to quantify these non-Darcy Flow effects. The fully coupled model can include EDM (Equilibrium Desorption Model) or DDM (Dynamic Desorption Model). In EDM, the gas sorption in the matrix system is a function of gas pressure only, i.e., the sorption process completes instantly when the cleat pressure changes. In DDM, the gas sorption in the matrix system is a function of both gas pressure in the cleat and the diffusion time in the matrix, i.e., a time lag between the cleat Flow and diffusion process in the matrix exists. When only Darcy Flow is assumed, this model was verified against both the model results of a vertical gas well performance by using ECLIPSE and field data from the Horseshoe Canyon coalbed gas well. Both EDM and DDM are applied to quantify the relationship among non-Darcy effect, production parameters, diffusion times, and coal seam compaction. Model results indicate that the non-Darcy effect is significant for high pressure drops and exists only within a small region near wellbore and that different diffusion times may produce two peaks of production rate, one is due to gas Flow in the cleat system at the early stage and the other is due to gas diffusion at the late stage. The coal seam compaction can reduce the production rate much more than the non-Darcy Flow effect at the early stage but has slightly impact at the late stage.
Thomas J R Hughes - One of the best experts on this subject based on the ideXlab platform.
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a stabilized mixed discontinuous galerkin method for Darcy Flow
Computer Methods in Applied Mechanics and Engineering, 2006Co-Authors: Thomas J R Hughes, Arif Masud, Jing WanAbstract:Abstract A new mixed, stabilized, discontinuous Galerkin formulation for Darcy Flow is presented. The formulation combines several attributes not simultaneously satisfied by other methods: It is convergent for any combination of velocity and pressure interpolation higher than first-order, it exactly satisfies a mass balance on each element, and it passes two- and three-dimensional constant-Flow “patch tests” for distorted element geometries. The key ingredient in the formulation is a volumetric, residual-based, stabilization term that does not involve any mesh-dependent parameters.
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a stabilized mixed finite element method for Darcy Flow
Computer Methods in Applied Mechanics and Engineering, 2002Co-Authors: Arif Masud, Thomas J R HughesAbstract:We develop new stabilized mixed finite element methods for Darcy Flow. Stability and an a priori error estimate in the ‘‘stability norm’’ are established. A wide variety of convergent finite elements present themselves, unlike the classical Galerkin formulation which requires highly specialized elements. An interesting feature of the formulation is that there are no mesh-dependent parameters. Numerical tests confirm the theoretical results. 2002 Elsevier Science B.V. All rights reserved.
John Killough - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of low velocity non Darcy Flow of gas and water in coal seams
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Gang Huang, Hongqing Song, Jiaosheng Yang, Yuhe Wang, John KilloughAbstract:Abstract Fluid Flow in low-permeability coal seams shows characteristics of low-velocity non-Darcy Flow. A two-phase mathematical Flow model considering the effect of the threshold pressure gradient (TPG) for gas and water transportation and Flow in such reservoirs has been developed. The corresponding numerical model has been formulated and solved. From the numerical results, we can conclude that both the gas production rate and cumulative gas production in the case when TPG is considered are always less than those in the cases when TPG is not considered because of the sharply decreased pressure and increased energy consumption. A comparison of the gas production rates obtained from the calculation results and from monitoring data indicates that the gas production rate predicted using the model with TPG is more accurate. Under the calculation conditions, the gas production rates when considering different values of TPG are approximately 35%–70% less than those for cases without TPG. In addition, the gas production rate and total gas production decrease as the bottom hole pressure and TPG increase, but they increase with the fracture half length. However, these factors have little influence on the water production regardless of the incorporation of TPG. The research expands the theoretical basis of gas recovery from the tight coal seams and provides a more accurate method to predict the gas production rate efficiently.
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numerical research on co2 storage efficiency in saline aquifer with low velocity non Darcy Flow
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Zhiyong Song, Hongqing Song, John Killough, Juliana Y Leung, Gang HuangAbstract:Low permeability saline aquifers, which are widely distributed around this world, have great potential for injected CO2 storage. Fluid Flow in low permeability layers shows characteristics of low-velocity non- Darcy Flow. A mathematical model considering the effect of threshold pressure gradient (TPG) for CO2 Flow and storage in low permeability saline aquifer has been developed, and the corresponding nu- merical model has been formulated and solved. From the numerical results, we can conclude that the injection rate, cumulative CO2 injected, and the storage efficiency for the case with TPG are always less than those of the case without TPG because of the sharp pressure decline and increased energy con- sumption. Under this paper's calculation condition, the storage efficiency when considering TPG is about 10% less than the case without considering TPG. If the TPG effect was to be ignored in the design of CO2 storage in low permeability saline aquifers, the CO2 storage efficiency will be overestimated. The research enlarges the theoretical basis of carbon capture and storage (CCS) and provides a more accurate method to evaluate CO2 storage efficiency. © 2015 Published by Elsevier B.V.
