Injection of gas (CO_(2)) into coal seams is an effective method to benefit from both CO_(2) geological storage and coalbed methane recovery. Based on the dual pore structure of coal mass, and the Weibull distribution...Injection of gas (CO_(2)) into coal seams is an effective method to benefit from both CO_(2) geological storage and coalbed methane recovery. Based on the dual pore structure of coal mass, and the Weibull distribution of fracture permeability, a menmal-hydraulic-mechanical (THM) coupling mathematical model is proposed involving the non-isothermal adsorption of binary gases, dynamic gas diffusion between matrix and fractures, multiphase seepage, coal deformation, heat conduction and heat convection. This mathematical model is applied to study the process of CO_(2)-enhanced coalbed methane recovery (CO_(2)-ECBM). Results show that the CH4 content of CO_(2)-ECBM in coal seam decreases significantly when compared with that of regular drainage, and decreases rapidly in the early stage but slowly in the later stage. Coal seam permeability evolution is triggered by changes in gas adsorption/desorption, temperature and effective stress. For regular drainage, the early permeability shows a decreasing trend dominated by the increase of effective stress, while the later permeability shows an increasing trend dominated by the CH4 desorption caused shrinkage of coal matrix. For CO_(2)-ECBM, the permeability in coal seam generally shows a downward trend due to both matrix swelling induced by gas adsorption and thermal expansion, particularly near injection well. There appears an increased and delayed peak production rate of CH4. The CH4 production rate of CO_(2)-ECBM is always higher than that of regular drainage. The CH4 cumulative production and CO_(2) cumulative storage linearly increase with time, and the CH4 cumulative production of CO_(2)-ECBM increased by 39.2% in the duration of 5000 d compared with regular drainage. Reasonable CO_(2) injection starting time can overcome the issue of early CO_(2) breakthrough and ineffective increase of CH4 production. In the studied case, the optimal injection starting time is 2500 d. Compared with the simultaneous CH4 extraction and CO_(2) injection, the CH4 cumulative production of 展开更多
运用热流固耦合理论,在岩石破裂过程分析系统(Rock Failure Process Analysis,RFPA)的基础上实现了温度-渗流-应力-损伤(Thermo-hydro-mechanical-damage,THMD)的多场耦合数值模型,并以此为工具进行了水工结构中温度场随渗流和应力而变...运用热流固耦合理论,在岩石破裂过程分析系统(Rock Failure Process Analysis,RFPA)的基础上实现了温度-渗流-应力-损伤(Thermo-hydro-mechanical-damage,THMD)的多场耦合数值模型,并以此为工具进行了水工结构中温度场随渗流和应力而变化的规律研究。结果表明,水的流动导致的热量迁移现象可以用于分析水工建筑物的水温异常,并可将其作为结构是否出现了渗漏的一种监测手段。对破坏过程中温度变化规律的数值试验研究表明:在初始加载阶段,试样中的原生裂隙随着应力的不断增加而闭合,导致透水能力以及渗流速度的降低,渗流对温度场的影响作用也随之而逐渐减小;但当试样中的应力水平达到其峰值强度时,损伤急剧增加并形成了渗漏通道,渗流速度增大,试样顶端的温度也急剧升高。数值模拟得到的温度场随渗流速度和方向、应力、破坏三因素的变化规律有助于完善温度探漏的相关理论。展开更多
The pressure solution model of granular aggregates was introduced into a FEM code which was developed for the analysis of thermo-hydro-mechanical(T-H-M) coupling in porous medium. Aimed at creating a hypothetical mode...The pressure solution model of granular aggregates was introduced into a FEM code which was developed for the analysis of thermo-hydro-mechanical(T-H-M) coupling in porous medium. Aimed at creating a hypothetical model of nuclear waste disposal in unsaturated quartz aggregate rock mass with laboratory scale, two 4-year computation cases were designed: 1) The porosity and permeability of rock mass are functions of the pressure solution; 2) The porosity and the permeability are constants. Calculation results show that the magnitude and distribution of stresses in the rock mass of these two calculation cases are roughly the same. And, the porosity and the permeability decrease to 43%-54% and 4.4%-9.1% of their original values after case 1 being accomplished; but the negative pore water pressures in cases 1 and 2 are respectively 1.0-1.25 and 1.0-1.1 times of their initial values under the action of nuclear waste. Case 1 exhibits the obvious effect of pressure solution.展开更多
文摘Injection of gas (CO_(2)) into coal seams is an effective method to benefit from both CO_(2) geological storage and coalbed methane recovery. Based on the dual pore structure of coal mass, and the Weibull distribution of fracture permeability, a menmal-hydraulic-mechanical (THM) coupling mathematical model is proposed involving the non-isothermal adsorption of binary gases, dynamic gas diffusion between matrix and fractures, multiphase seepage, coal deformation, heat conduction and heat convection. This mathematical model is applied to study the process of CO_(2)-enhanced coalbed methane recovery (CO_(2)-ECBM). Results show that the CH4 content of CO_(2)-ECBM in coal seam decreases significantly when compared with that of regular drainage, and decreases rapidly in the early stage but slowly in the later stage. Coal seam permeability evolution is triggered by changes in gas adsorption/desorption, temperature and effective stress. For regular drainage, the early permeability shows a decreasing trend dominated by the increase of effective stress, while the later permeability shows an increasing trend dominated by the CH4 desorption caused shrinkage of coal matrix. For CO_(2)-ECBM, the permeability in coal seam generally shows a downward trend due to both matrix swelling induced by gas adsorption and thermal expansion, particularly near injection well. There appears an increased and delayed peak production rate of CH4. The CH4 production rate of CO_(2)-ECBM is always higher than that of regular drainage. The CH4 cumulative production and CO_(2) cumulative storage linearly increase with time, and the CH4 cumulative production of CO_(2)-ECBM increased by 39.2% in the duration of 5000 d compared with regular drainage. Reasonable CO_(2) injection starting time can overcome the issue of early CO_(2) breakthrough and ineffective increase of CH4 production. In the studied case, the optimal injection starting time is 2500 d. Compared with the simultaneous CH4 extraction and CO_(2) injection, the CH4 cumulative production of
文摘运用热流固耦合理论,在岩石破裂过程分析系统(Rock Failure Process Analysis,RFPA)的基础上实现了温度-渗流-应力-损伤(Thermo-hydro-mechanical-damage,THMD)的多场耦合数值模型,并以此为工具进行了水工结构中温度场随渗流和应力而变化的规律研究。结果表明,水的流动导致的热量迁移现象可以用于分析水工建筑物的水温异常,并可将其作为结构是否出现了渗漏的一种监测手段。对破坏过程中温度变化规律的数值试验研究表明:在初始加载阶段,试样中的原生裂隙随着应力的不断增加而闭合,导致透水能力以及渗流速度的降低,渗流对温度场的影响作用也随之而逐渐减小;但当试样中的应力水平达到其峰值强度时,损伤急剧增加并形成了渗漏通道,渗流速度增大,试样顶端的温度也急剧升高。数值模拟得到的温度场随渗流速度和方向、应力、破坏三因素的变化规律有助于完善温度探漏的相关理论。
基金Project(2010CB732101)supported by the National Key Basic Research and Development Program of ChinaProjects(51079145,51379201)supported by the National Natural Science Foundation of China
文摘The pressure solution model of granular aggregates was introduced into a FEM code which was developed for the analysis of thermo-hydro-mechanical(T-H-M) coupling in porous medium. Aimed at creating a hypothetical model of nuclear waste disposal in unsaturated quartz aggregate rock mass with laboratory scale, two 4-year computation cases were designed: 1) The porosity and permeability of rock mass are functions of the pressure solution; 2) The porosity and the permeability are constants. Calculation results show that the magnitude and distribution of stresses in the rock mass of these two calculation cases are roughly the same. And, the porosity and the permeability decrease to 43%-54% and 4.4%-9.1% of their original values after case 1 being accomplished; but the negative pore water pressures in cases 1 and 2 are respectively 1.0-1.25 and 1.0-1.1 times of their initial values under the action of nuclear waste. Case 1 exhibits the obvious effect of pressure solution.
