致密气藏岩石渗透率应力敏感对气水两相流动影响实验研究

Gas/water Flowing Ability Influence Experimental Study of Permeability Stress Sensibility in Tight Gas Reservoir

以长庆油田致密气藏P1s、P2h储层岩心为例,基于应力敏感实验,讨论了岩石渗透率应力敏感对致密储气层气水两相流动及产能的影响。研究了不同围压下气水相对渗透率变化趋势。实验结果表明,在相同渗透率条件下,围压增加岩心喉道和较大孔隙受到压缩而发生变形,导致气水相对渗透率值整体下降。在相同应力条件下,气驱过程中孔隙结构越好,气水两相渗流能力越强。气驱水分流曲线表明,围压越大气驱水过程见水越早,气驱水效果越差;相同围压下,渗透率越高气驱水过程见水越晚,气驱水效果越好。对于致密气藏,应力敏感产生的绝对变化值不大,但相对变化值较大,对致密储层渗透率以及气水两相流动影响较大,因而它对产能的影响不容忽视。

Taking cores of P1s and P2h formation from tight gas reservoir in Changqing oilfield as an example, we discuss the gas/water flowing ability and production influence of permeability stress sensibility based on stress sensitivity experiments. The gas/water relative permeability change trend in different confining pressures is studied. The experiment results show that in the same permeability, when the confining pressures increase, core pore throat and bigger pore deformed with compression, which leads to overall drop of gas/water relative permeability. At the same stress condition, the better the pore structure in the process of gas injection, the stronger the gas/water two phase filtration capacity. Gas driving water distribution curve shows that when the confining pressure is large, the water appears soon in the process of gas driving water process, and the gas driving water effect is worse. In the same confining pressure, the higher the reservoir permeability, the later the water appearance in the process of gas driving water, the better the gas driving water effect. In tight gas reservoir, the absolute value changes caused by stress sensibility are not big, but the relative value changes are great. It influences tight reservoir permeahility and gas/water flowing characteristics a lot, and its affect on reservoir productivity can not be ignored.