玛西斜坡百口泉组致密砂砾岩储层速敏特征及主控因素

Velocity-sensitive characteristics and main controlling factors of tight glutenite reservoirs in Baikouquan Formation of Maxi slope

新疆砂砾岩油藏储层碎屑粒径分布范围广,非均质性强,针对这类储层速敏性强、且速敏主控因素不明的问题,采取薄片分析、扫描电镜、高压压汞、速敏性试验等手段对玛西斜坡百口泉组岩心进行分析评价。结果表明:黏土矿物含量对样品速敏影响较弱;物性是影响砂砾岩储层敏感性的主要因素,渗透率比整体随着流速增加呈现先快速下降然后缓慢下降的现象;当液测渗透率小于0.1×10^(-3)μm^(2)时,随着储层物性变好,喉道逐渐变大,一些原本难以通过喉道的矿物等可以随着流体流动通过喉道,速敏指数随着液测渗透率增加而下降;当液测渗透率大于0.1×10^(-3)μm^(2)时,参与渗流的喉道半径变化小,但孔隙之间连通性好,连通喉道多,更多的原本在孔隙内没有运动的黏土矿物也开始随着驱替流体发生运动,当矿物足够多的时候会堵塞喉道,导致渗透率下降,速敏指数则随着液测渗透率增大而增大。

The glutenite reservoir in Xinjiang have a strong velocity(flow rate)sensitivity and its main control factors are not clear because of its wide particle size distribution and strong heterogeneity.In this study,different techniques were used for core analysis with core samples from Baikouquan Formation in Maxi slope,including thin section analysis,scanning electron microscope,high-pressure mercury injection and velocity sensitivity experiments.The results show that the clay minerals content has a weak influence on the velocity sensitivity of the samples,while the physical property is the main factor affecting the sensitivity of the glutenite reservoir,and the permeability ratio decreases rapidly at first and then slowly declines with the increase of flow rate.When the permeability is less than 0.1×10^(-3)μm^(2),with the improvement of reservoir physical properties,the throat gradually becomes larger,and some minerals(particles)that were difficult to pass through the throat can pass through the throat along with the fluid flow,and so the velocity sensitivity index decreases with the improvement of permeability.When the permeability is greater than 0.1×10^(-3)μm^(2),the throat radius involved in flow changes little,but the pores are well connected and there are many connected throats.More clay minerals that did not move firstly in the pores begin to move along with the flowing displacement fluid.But when there are enough minerals(particles),the throat can be blocked,resulting in the decrease of permeability and the increase of velocity sensitivity index with the improvement of permeability.