Source-rock permeability is a key parameter that controls the gas production rate from unconventional reservoirs. Measured source-rock permeability in the laboratory, however, is not an intrinsic property of a rock sa...Source-rock permeability is a key parameter that controls the gas production rate from unconventional reservoirs. Measured source-rock permeability in the laboratory, however, is not an intrinsic property of a rock sample, but depends on pore pressure and temperature as a result of the relative importance of slip flow and diffusion in gas flow in lowpermeability media. To estimate the intrinsic permeability which is required to determine effective permeability values for the reservoir conditions, this study presents a simple approach to correct the laboratory permeability measurements based on the theory of gas flow in a micro/nano-tube that includes effects of viscous flow, slip flow and Knudsen diffusion under different pore pressure and temperature conditions. The approach has been verified using published shale laboratory data.The ＇＇corrected＇＇（or intrinsic） permeability is considerably smaller than the measured permeability. A larger measured permeability generally corresponds to a smaller relative difference between measured and corrected permeability values. A plot based on our approach is presented to describe the relationships between measured and corrected permeability for typical Gas Research Institute permeability test conditions. The developed approach also allows estimating the effective permeability in reservoir conditions from a laboratory permeability measurement.展开更多
Due to the nanometer scale pore size and extremely low permeability of a shale matrix,traditional Darcy＇s law can not exactly describe the combined gas transport mechanisms of viscous flow and Knudsen diffusion.Three...Due to the nanometer scale pore size and extremely low permeability of a shale matrix,traditional Darcy＇s law can not exactly describe the combined gas transport mechanisms of viscous flow and Knudsen diffusion.Three transport models modified by the Darcy equation with apparent permeability are used to describe the combined gas transport mechanisms in ultra-tight porous media,the result shows that Knudsen diffusion has a great impact on the gas transport and Darcy＇s law cannot be used in a shale matrix with a pore diameter less than 1 μm.A single porosity model and a double porosity model with consideration of the combined gas transport mechanisms are developed to evaluate the influence of gas transport mechanisms and fracture parameters respectively on shale gas production.The numerical results show that the gas production predicted by Darcy＇s law is lower than that predicted with consideration of Knudsen diffusion and the tighter the shale matrix,the greater difference of the gas production estimates.In addition,the numerical simulation results indicate that shale fractures have a great impact on shale gas production.Shale gas cannot be produced economically without fractures.展开更多
Ordered mesoporous carbon（OMC） with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound（VOC）disposal. Benzene, cyclohexane and hexane w...Ordered mesoporous carbon（OMC） with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound（VOC）disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.展开更多
In all the existing apparent permeability calculation models used for shale gas,the effect of surface diffusion of adsorbed gas is neglected and shale gas is assumed to be in an ideal state,so the calculation results ...In all the existing apparent permeability calculation models used for shale gas,the effect of surface diffusion of adsorbed gas is neglected and shale gas is assumed to be in an ideal state,so the calculation results may not reflect the real situations.In this paper,a new apparent permeability model suitable for the shale gas of real state was developed by seepage mechanics method.In this model,the influential factors(e.g.the viscous flow and Knudsen diffusion of free gas and the surface diffusion of adsorbed gas)are taken into account to present the real flowing situations of shale gas in nanopores.Then,the accuracy of this new apparent permeability model was verified by comparing its calculation results with the experimental data.Finally,all factors influencing the apparent permeability of shale gas were analyzed in this new model.It is shown that the apparent permeability of shale gas is most affected by pressure and pore radius,and less by relative molecular mass and blockage coefficient.Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat mainly affect the fraction of permeability contributed by surface diffusion.Besides,the effects of each factor on apparent permeability and permeability fraction under low pressure are different from those under high pressure.Under low pressure,the effects of temperature and pore radius on apparent permeability are more obvious,and the effects of temperature,pore radius,Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat on the fraction of permeability are also more obvious.Finally,when the pressure is low and the pore radius is small,the surface diffusion is dominant.When the pressure is high and the pore radius is large,the viscous flow is dominant.In the case of small pore radius or low pressure,the surface diffusion shall not be neglected.展开更多
文摘Source-rock permeability is a key parameter that controls the gas production rate from unconventional reservoirs. Measured source-rock permeability in the laboratory, however, is not an intrinsic property of a rock sample, but depends on pore pressure and temperature as a result of the relative importance of slip flow and diffusion in gas flow in lowpermeability media. To estimate the intrinsic permeability which is required to determine effective permeability values for the reservoir conditions, this study presents a simple approach to correct the laboratory permeability measurements based on the theory of gas flow in a micro/nano-tube that includes effects of viscous flow, slip flow and Knudsen diffusion under different pore pressure and temperature conditions. The approach has been verified using published shale laboratory data.The ＇＇corrected＇＇（or intrinsic） permeability is considerably smaller than the measured permeability. A larger measured permeability generally corresponds to a smaller relative difference between measured and corrected permeability values. A plot based on our approach is presented to describe the relationships between measured and corrected permeability for typical Gas Research Institute permeability test conditions. The developed approach also allows estimating the effective permeability in reservoir conditions from a laboratory permeability measurement.
基金supported by the National Natural Science Foundation of China (No. 51234007, No. 11072268)Program for Changjiang Scholars and Innovative Research Team in University (IRT1294)+5 种基金the Major Programs of Ministry of Education of China (No. 311009)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20110133120012)the National Natural Science Foundation of Shandong Province (No. 11072268)the Fundamental Research Funds for the Central Universities (No. 11CX05007A)the Fundamental Research Funds for the Central Universities (No. 11CX04022A)Introducing Talents of Discipline to Universities (B08028)
文摘Due to the nanometer scale pore size and extremely low permeability of a shale matrix,traditional Darcy＇s law can not exactly describe the combined gas transport mechanisms of viscous flow and Knudsen diffusion.Three transport models modified by the Darcy equation with apparent permeability are used to describe the combined gas transport mechanisms in ultra-tight porous media,the result shows that Knudsen diffusion has a great impact on the gas transport and Darcy＇s law cannot be used in a shale matrix with a pore diameter less than 1 μm.A single porosity model and a double porosity model with consideration of the combined gas transport mechanisms are developed to evaluate the influence of gas transport mechanisms and fracture parameters respectively on shale gas production.The numerical results show that the gas production predicted by Darcy＇s law is lower than that predicted with consideration of Knudsen diffusion and the tighter the shale matrix,the greater difference of the gas production estimates.In addition,the numerical simulation results indicate that shale fractures have a great impact on shale gas production.Shale gas cannot be produced economically without fractures.
基金the State Key program of National Natural Science Foundation (No. 21337003)the Strategic Priority Research Program (No. XDB05050200)+2 种基金the National High Technology Research and Development Program of China (2012AA063101)the Special Environmental Protection Foundation for Public Welfare Project (No. 201309073)the Team Interaction and Cooperation of the Science and Technology Program of the Chinese Academy of Sciences
文摘Ordered mesoporous carbon（OMC） with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound（VOC）disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.
基金Project supported by the National Major Science and Technology Project“Research on Flow Mechanism and Numerical Simulation of Shale Oil in Chang 7 in South Hubei Province”(No.:2017ZX05049-006)the National Natural Science Foundation of China“Multi-scale Transport Mechanism and Numerical Simulation of Shale Oil”(No.:51674279).
文摘In all the existing apparent permeability calculation models used for shale gas,the effect of surface diffusion of adsorbed gas is neglected and shale gas is assumed to be in an ideal state,so the calculation results may not reflect the real situations.In this paper,a new apparent permeability model suitable for the shale gas of real state was developed by seepage mechanics method.In this model,the influential factors(e.g.the viscous flow and Knudsen diffusion of free gas and the surface diffusion of adsorbed gas)are taken into account to present the real flowing situations of shale gas in nanopores.Then,the accuracy of this new apparent permeability model was verified by comparing its calculation results with the experimental data.Finally,all factors influencing the apparent permeability of shale gas were analyzed in this new model.It is shown that the apparent permeability of shale gas is most affected by pressure and pore radius,and less by relative molecular mass and blockage coefficient.Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat mainly affect the fraction of permeability contributed by surface diffusion.Besides,the effects of each factor on apparent permeability and permeability fraction under low pressure are different from those under high pressure.Under low pressure,the effects of temperature and pore radius on apparent permeability are more obvious,and the effects of temperature,pore radius,Langmuir maximum adsorption capacity,Langmuir pressure and isothermal adsorption heat on the fraction of permeability are also more obvious.Finally,when the pressure is low and the pore radius is small,the surface diffusion is dominant.When the pressure is high and the pore radius is large,the viscous flow is dominant.In the case of small pore radius or low pressure,the surface diffusion shall not be neglected.
