摘要
为研究页岩气开采过程中有效应力、气体吸附及滑脱效应作用下微裂隙表观渗透率的演化机制,利用分形理论表征微裂隙气体总流量,并基于Hagen-Poiseuille二阶滑脱方程建立微裂隙变形和滑脱效应综合作用的表观渗透率模型。同时,结合滑脱系数与固有渗透率间的函数关系,量化有效应力和气体吸附等因素对滑脱系数的影响,探讨页岩气渗流过程中滑脱系数动态演变过程,并验证模型可靠性。此外,结合敏感性分析,探讨微裂隙压缩性系数、分形维数、内膨胀系数对滑脱系数的影响。结果表明:(1)恒定外应力和恒定有效应力条件下,随孔隙压力逐渐增大,受气体吸附与滑脱效应的耦合影响,表观渗透率呈减小趋势;(2)当外应力恒定时,气体分子平均自由程随孔隙压力增大而减小,滑脱效应减弱,一阶、二阶滑脱系数C_(1)、C_(2)减小,整体滑脱系数B增大;当有效应力恒定时,页岩气渗流通道受制于气体吸附的影响而逐渐减小,C_(1)、C_(2)和B逐渐增大;(3)基于模型敏感性分析,探讨微裂隙压缩性系数、分形维数、内膨胀系数与滑脱系数之间的互馈机制,其中微裂隙压缩性系数、分形维数导致固有渗透率增大,而C_(1)、C_(2)、B减小;内膨胀系数的增大导致固有渗透率减小,C_(1)、C_(2)、B增大。研究所得结论将为页岩气开采提供一定的理论支撑。
In order to study the evolution mechanism of microfracture apparent permeability under the effect of effective stress,gas adsorption and slip effect during shale-gas extraction,the fractal theory was used to characterize the total gas flow in microfracture,and an apparent permeability model of the combined effects of microfracture deformation and slip effect based on the Hagen-Poiseuille secondorder slip equation was established.Meanwhile,the influence of effective stress and gas adsorption on the slip coefficient was quantified by combining with the functional relationship between the slip coefficient and intrinsic permeability,the dynamic evolution of the slip coefficient during shale-gas seepage was explored,and the reliability of the model was verified.In addition,the effects of microfracture compressibility coefficient,fractal dimension and internal expansion coefficient on slip coefficient were explored in conjunction with sensitivity analysis.The results shown that:①Under the conditions of constant external and effective stress,the apparent permeability tended to decrease with the gradual increase of pore pressure,which was influenced by the coupling of gas adsorption and slip effect;②When the external stress was constant,the average free range of gas molecules decreased with increasing pore pressure,the slip effect was weakened,the first-order and second-order slip coefficients C_(1) and C_(2) decreased,and the overall slip coefficient B increased.When the effective stress was constant,the shale-gas seepage channel was subject to gas adsorption and gradually reduced,and C_(1),C_(2) and B gradually increased;③Based on the model sensitivity analysis,the reciprocal feedback mechanism between microfracture compressibility coefficient,fractal dimension,internal expansion coefficient and slip coefficient was explored,in which the microfracture compressibility coefficient and fractal dimension led to an increase in intrinsic permeability,and a decrease in C_(1),C_(2) and B decrease.The increase of internal expansion coefficient led to an decrease in the intrinsic permeability,and an increase in C_(1),C_(2) and B.The findings of this study will provide some theoretical support for shale-gas extraction.
作者
丁云娜
李波波
成巧耘
段淑蕾
宋浩晟
DING Yunna;LI Bobo;CHENG Qiaoyun;DUAN Shulei;SONG Haosheng(College of Mining,Guizhou University,Guiyang 550025,China;The National Joint Engineering Laboratory for the Utilization of Dominant Mineral Resources in Karst area,Guizhou University,Guiyang 550025,China;Guizhou Key Laboratory of Comprehensive Utilization of Non-metallic Mineral Resources,Guiyang 550025,China)
出处
《煤炭科学技术》
EI
CAS
CSCD
北大核心
2023年第11期129-138,共10页
Coal Science and Technology
基金
国家自然科学基金资助项目(52274183,52064007)
贵州省省级科技计划资助项目(黔科合基础-ZK[2021]重点052)。
关键词
页岩气开采
有效应力
气体吸附
滑脱系数
表观渗透率
分形理论
shale gas exploration
effective stress
gas adsorption
slip coefficient
apparent permeability
fractal theory
作者简介
丁云娜(1997-),女,贵州遵义人,硕士研究生。E-mail:2632929023@qq.com;通讯作者:李波波(1985-),男,贵州修文人,教授,博士生导师。E-mail:bbli@gzu.edu.cn。
