低渗砂岩储层渗透率各向异性规律的实验研究

Experiment on anisotropy of permeability with tight sandstone

应用1摩尔/升的盐水作为孔隙介质,采用液体压力脉冲法对采自鄂尔多斯盆地某油田三叠系延长组低渗砂岩样品进行了渗透率随有效应力的变化规律实验研究.在围压0～100MPa,孔隙压力0～12MPa范围内,样品的渗透率变化范围在0～60×10-18 m2之间,实验结果表明样品的渗透率随有效应力的增加而减少.通过拟合实验结果,得到渗透率随有效应力的变化规律较好的符合幂函数关系,相关系数介于0.903～0.984之间.同时对同一样品的X,Y,Z相互垂直三个方向的渗透率随有效应力的变化进行了比较,结果表明渗透率的各向异性同样是压力的函数,且随着有效应力的增加,不同平面内的渗透率各向异性表现出了不同的变化规律.但在实验压力范围内,渗透率各向异性皆为正值,表明在有效应力为100MPa范围内孔隙内流体的流动方向未发生改变.研究结果为鄂尔多斯盆地低渗(超低渗)油气田开发,特别是对深部油气田开发过程中开发方式的选择与设计,充分利用渗透率各向异性的特点,提高采收率提供了新的岩石物性资料.

Permeability and permeability anisotropy of low permeable sandstone reservoir recovered from the Ordos Basin Triassic formation and saturated with 1 M NaC1 solution was researched by the fluid pulse method. Permeability of the low permeable sandstone varies from 0~60 × 10^0 18 m2 at confining pressure 0~ 100 MPa, pore pressure 0 ~ 12 MPa. The results show that permeability of low permeable sandstone decreases with effective pressure increasing. Through fitting the test results with trendline, the relationship between permeability and effective pressure is true for the power function. The correlation coefficient is among 0. 903~0. 984. At the same time, through comparing the permeability of vertical each other X,Y and Z directions, the anisotropy of permeability also is the function of effective pressure, and it have different rule with effective pressure increasing, but the preferred flow direction don＇t change with effective pressure increasing in the experimental pressure. All researches provide new rock physics properties for the development of low permeable oil and gas reservoir, especially for the deeper oil and gas resource exploring and development, the choice of development style, enhanced oil recovery in Ordos Basin.