Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating...Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.展开更多
Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reser...Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reservoir in Southern Qinshui Basin. Flow patterns of methane and water in pore-fracture system and hydraulic fracture were discussed by using limit method and average method. Based on the structure model and flow pattern of post-fracturing high-rank coal reservoir, flow patterns of methane and water were established. Results show that seepage pattern of methane in pore-fracture system is linked with pore diameter, fracture width, coal bed pressure and flow velocity. While in hydraulic fracture, it is controlled by fracture height, pressure and flow velocity. Seepage pattern of water in pore-fracture system is linked with pore diameter, fracture width and flow velocity. While in hydraulic fracture, it is controlled by fracture height and flow velocity. Pores and fractures in different sizes are linked up by ultramicroscopic fissures, micro-fissures and hydraulic fracture. In post-fracturing high-rank coal reservoir, methane has level-three flow and gets through triple medium to the wellbore; and water passes mainly through double medium to the wellbore which is level-two flow.展开更多
In this paper, influences on the reservoir permeability, the reservoir architecture and the fluid flow pattern caused by hydraulic fracturing are analyzed. Based on the structure and production fluid flow model of pos...In this paper, influences on the reservoir permeability, the reservoir architecture and the fluid flow pattern caused by hydraulic fracturing are analyzed. Based on the structure and production fluid flow model of post fracturing high-rank coal reservoir, Warren-Root Model is improved. A new physical model that is more suitable for post fracturing high-rank coal reservoir is established. The results show that the width, the flow conductivity and the permeability of hydraulic fractures are much larger than natural fractures in coal bed reservoir. Hydraulic fracture changes the flow pattern of gas and flow channel to wellbore, thus should be treated as an independent medium. Warrant-Root Model has some limitations and can’t give a comprehensive interpretation of seepage mechanism in post fracturing high-rank coal reservoir. Modified Warrant-Root Model simplifies coal bed reservoir to an ideal system with hydraulic fracture, orthogonal macroscopic fracture and cuboid matrix. Hydraulic fracture is double wing, vertical and symmetric to wellbore. Coal bed reservoir is divided into cuboids by hydraulic fracture and further by macroscopic fractures. Flow behaviors in coal bed reservoir are simplified to three step flows of gas and two step flows of water. The swap mode of methane between coal matrix and macroscopic fractures is pseudo steady fluid channeling. The flow behaviors of methane to wellbore no longer follow Darcy’s Law and are mainly affected by inertia force. The flow pattern of water follows Darcy’s Law. The new physical model is more suitable for post fracturing high-rank coal reservoir.展开更多
基金financially supported by the Natural Science Foundation of China (No.41802192)the National Science and Technology Key Special Project of China (No.2016ZX05044-002 and No.2016ZX05043)+2 种基金the Shanxi Provincial Basic Research Program-Coal Bed Methane Joint Research Foundation (No.2012012001 and No.2015012014)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining (No.SHJT-17-42.18)the Fundamental Research Funds for the Central Universities (No.CUGL170811)
文摘Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.
基金Projects(41330638,41272154)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),ChinaProject(2014M551705)supported by the China Postdoctoral Science Foundation
文摘Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reservoir in Southern Qinshui Basin. Flow patterns of methane and water in pore-fracture system and hydraulic fracture were discussed by using limit method and average method. Based on the structure model and flow pattern of post-fracturing high-rank coal reservoir, flow patterns of methane and water were established. Results show that seepage pattern of methane in pore-fracture system is linked with pore diameter, fracture width, coal bed pressure and flow velocity. While in hydraulic fracture, it is controlled by fracture height, pressure and flow velocity. Seepage pattern of water in pore-fracture system is linked with pore diameter, fracture width and flow velocity. While in hydraulic fracture, it is controlled by fracture height and flow velocity. Pores and fractures in different sizes are linked up by ultramicroscopic fissures, micro-fissures and hydraulic fracture. In post-fracturing high-rank coal reservoir, methane has level-three flow and gets through triple medium to the wellbore; and water passes mainly through double medium to the wellbore which is level-two flow.
基金supported by the National Natural Science Foundation of China (Nos. 41330638, 41272154, 51325403, 51104148, and 51204162)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1302049B)
文摘In this paper, influences on the reservoir permeability, the reservoir architecture and the fluid flow pattern caused by hydraulic fracturing are analyzed. Based on the structure and production fluid flow model of post fracturing high-rank coal reservoir, Warren-Root Model is improved. A new physical model that is more suitable for post fracturing high-rank coal reservoir is established. The results show that the width, the flow conductivity and the permeability of hydraulic fractures are much larger than natural fractures in coal bed reservoir. Hydraulic fracture changes the flow pattern of gas and flow channel to wellbore, thus should be treated as an independent medium. Warrant-Root Model has some limitations and can’t give a comprehensive interpretation of seepage mechanism in post fracturing high-rank coal reservoir. Modified Warrant-Root Model simplifies coal bed reservoir to an ideal system with hydraulic fracture, orthogonal macroscopic fracture and cuboid matrix. Hydraulic fracture is double wing, vertical and symmetric to wellbore. Coal bed reservoir is divided into cuboids by hydraulic fracture and further by macroscopic fractures. Flow behaviors in coal bed reservoir are simplified to three step flows of gas and two step flows of water. The swap mode of methane between coal matrix and macroscopic fractures is pseudo steady fluid channeling. The flow behaviors of methane to wellbore no longer follow Darcy’s Law and are mainly affected by inertia force. The flow pattern of water follows Darcy’s Law. The new physical model is more suitable for post fracturing high-rank coal reservoir.
