摘要
页岩气储层为双重介质结构,包含裂缝系统和基质孔隙系统.在页岩中,裂缝从微米级到毫米级变化,基质孔隙则为纳米级.不同级别储集空间的发育导致页岩气的运移方式异于常规气藏,其过程是一个包含从宏观尺度到分子尺度的复杂运移过程.为深入了解页岩气运移方式,采用多孔介质中气体运移方式划分原理,利用Knudsen数对不同尺度的页岩气运移方式进行判断.从页岩气的分子平均自由程出发,计算页岩气在不同温度和压力下的分子平均自由程,结合裂缝和基质孔隙的尺度大小,分别计算裂缝和基质孔隙的Knudsen数,确定了裂缝中页岩气存在达西流（非达西流）和滑脱流2种运移方式,基质孔隙中页岩气则可能存在达西流（非达西流）、滑脱流和过渡流3种运移方式.通过绘制临界Knudsen数曲线,建立双对数的页岩气运移方式判定图版,运用该图版可以判断不同压力和孔隙直径下的页岩气运移方式,为准确认识页岩气的运移方式提供了理论依据.
Shale gas reservoir is characterized by dual-media structure, including fracture and matrix pore sys- tems. In the shale, the fractures change from micro-scale to milli-seale, in the matrix pores, the level is shown by nano-scale, the developments of different sizes of accumulating spaces result in the different migration modes from the conventional gas reservoirs, the change process is a complex migration course from macro-scale to molecular scale. In order to further understand the migration mode, with the help of the classifying principle of the gas migra- tion mode in porous media, the migration modes of the shale gas with different scales are identified by means of Knudsen numbers. From the viewpoints of the mean free paths of the shale gas molecules, the paths under different temperatures and pressures are calculated, and moreover integrating with the sizes of the fractures and matrix pores, the Knudsen numbers of them are seperatively computed, and then two kinds of migration modes including Darcy flow （ non-Darcy flow） and slip flow are determined in the shale gas of the fractures; while there may be three kinds of migration modes besides the transitional flow in the matrix pores. Through mapping the curves of the criti- cal Knudsen numbers, the identifying log-log chart boards of the shale gas migration modes are established. Thus the modes under different pressures and pore diameters can be identified with the help of the above chart boards, so the theoretical references can be provided for accurate identification and understanding of the shale gas migration modes.
出处
《大庆石油地质与开发》
CAS
CSCD
北大核心
2014年第4期166-170,共5页
Petroleum Geology & Oilfield Development in Daqing
基金
国家高技术研究发展计划(863计划)课题(2013AA064501)
陕西省科技统筹创新工程项目(2012KTZ0303-01)
陕西延长石油(集团)有限责任公司研究院青年基金项目(YJY2012-QNJJ-12)
关键词
页岩气
裂缝
基质
孔隙
运移方式
评价
确定图版
shale gas
fracture
matrix pore
migration mode
evaluation
determining chart board
