鄂尔多斯盆地长7致密储层可动流体分布特征

A study on distribution features of movable fluids for Chang 7 tight reservoir in Ordos Basin

鄂尔多斯盆地长7致密油资源丰富,储层地面空气渗透率小于0.3×10-3μm2,物性较差,可动流体饱和度是该类储层评价的关键参数之一。采用离心实验和核磁共振T2谱分析技术相结合的方法,开展了鄂尔多斯盆地长7致密储层可动流体分布特征研究,研究结果表明:一是长7致密储层单相可动水饱和度平均为39.40%,其中微米级(大于1μm)、亚微米级(0.1~1.0μm)及纳米级(小于0.1μm)可动水饱和度分别为2.2%、25.67%及11.52%;岩心束缚水下可动油含量平均为26.07%,其中微米级(大于1μm)、亚微米级(0.1~1.0μm)及纳米级(小于0.1μm)可动油含量分别为0.79%、9.48%及15.81%;可动流体主要分布在亚微米和纳米孔喉中。二是随着岩心渗透率的增大,可动水和可动油饱和度都增大;但不同喉道半径控制的可动流体饱和度增加幅度不同,喉道半径为0.10~0.5μm的可动流体饱和度随着岩心渗透率的增大都增大,且增幅最大,其次是喉道半径处于0.5~1.0μm的可动流体,喉道半径大于1.0μm的可动流体饱和度增幅最小,而喉道半径小于0.1μm的可动流体饱和度相对含量降低的趋势比较明显。

Ordos Basin is abundant in tight oil resource in Chang 7 Formation.Physical properties are poor in the reservoir with air permeability of less than 0.3×10^-3μm^2.This reservoir can be evaluated by movable fluid saturation which is considered as one of the most significant parameters. Combined with centrifuge tests and NMR T2 spectrum analysis, the movable fluids distribution of Chang 7 tight reservoir in Ordos Basin was figured out.The results show that：firstly, the average mono-phase saturation of movable water in Chang 7 tight oil reservoirs is 39.40%.While the movable water saturation in the pore throat which are divided to micron （greater than μm）,sub-micron（0.1 to 1μm） or nano（less than 0.1μm）,are respectively 2.2%,25.67% and 11.52%;the average movable oil saturation is 26.07% in bound water saturation,and the movable oil saturation in micron, submicron or nano-pore throat is 0.79 %, 9.48%and 15.81%, respec- tively; the movable fluids exist mainly in the submieron and nano-pore throat.Second,the movable water or oil saturation will increase with the increase of core permeability, but the trends of movable fluids satura- tion differ from the size of pore throat.When throat radius is 0.1 to 0.5 micrometer,the movable fluids sat- uration increases the biggest growth with core permeability,next is the radius of 0.5 to 1.0 micrometer,and the radius greater than 1.0 micrometer,the growth is the least.However,when throat radius is less than 0. 1 micrometer,the relative contents of movable fluids saturation decrease obviously.