摘要
基于页岩基质的纳米尺度孔隙特征,分析了页岩气在纳米孔隙中渗流的扩散、滑脱和达西渗流等对页岩气流动流量的影响.压差作用下页岩气流量的特征研究表明:达西流动产生的流量与地层压力、压力梯度和渗透率成正比;扩散引发的流量与压力梯度成正比,与平均压力成反比,与渗透率无关;滑脱引发的流量与压力梯度、渗透率成正比,压力梯度和渗透率一定时,滑脱流量为定值,与地层平均压力无关.低压下,气体的扩散效应和滑脱效应明显,扩散产生的流量所占比例较大,高压下渗流以达西流为主;在整个从低压到高压的地层压力区间,在低压下由于扩散作用,总的页岩气有一定的流量,随着地层压力的增大扩散产生的流量减小,到一定值后随着达西流量的进一步增大,总流量随地层压力的增加而增大,说明页岩气生产中存在一个最低效生产的压力区域.水在页岩薄片上吸水过程近似分为三个阶段:(1)水在页岩薄片表面的快速吸附;(2)水在裂缝中较快速度的渗吸;(3)水沿着微裂缝的缓慢渗吸.为页岩气开发中的压裂水的反排特征研究提供了理论基础.
Based on the nano-sacle of pores in shale rock, the influences of diffusion, flow slippage and Darcy＇s flow to shale gas flow rate in shale rock matrix are studied. The results of shale gas flow rate drived by pressure drop show that： the Darcy＇s flow rate is proportional to average zone pressure, pressure drop and permeability of shale rock matrix; The flow induced by diffusion is proportional to average pressure and pressure drop, but is inverse proportional to average zone pressure; The increment flow rate induced by slippage is proportional to pressure drop and permeability of shale rock matrix, but is independent of average zone pressure. In low pressure of shale rock zones, the diffusion flow and slip flow is very significient, and which have large ratios in whole flow rate; In big pressure the Drarcy＇s flow is mainly flow rate, and the diffusion flow and slip flow can be neglected. The shale gas flow rate decreases with pressure increasing in low zone pressure because of diffusion and slip flow, then the shale gas flow rate increases with pressure increasing when the zone pressure is bigger than one certain value, which shows that there is a low efficient pressure region for shale gas production. Water-imbibition on shale sheets approximately consist of three stages：（1） water rapid adsorption on shale sheet surface;（2） faster water imbition in the cracks;（3） slow water imbition along micro-cracks. It provides a theoretical basis for the study of characteristics of the inverse of fracturing water in shale gas development.
出处
《中国科学：技术科学》
EI
CSCD
北大核心
2016年第2期120-126,共7页
Scientia Sinica(Technologica)
基金
国家重点基础研究发展计划(批准号:2013CB228002)
国家自然科学基金(批准号:11472246)资助项目
关键词
页岩气
扩散
滑脱
达西定律
渗吸
shale gas
diffusion
slippage
Darcy＇s law
water imbition
