川西须家河组致密砂岩储层绿泥石成因及其与优质储层关系

Genesis of chlorites and its relationship with high-quality reservoirs in the Xujiahe Formation tight sandstones, western Sichuan depression

孙全力 孙晗森 贾趵 禹建军 罗文军

Sun Quanli Sun Hansen Jia Bao Yu Jianjun Luo Wenjun

致密气藏产气量在我国天然气总产量中所占比例越来越大,但由于其气藏分布复杂、储层预测难度大等因素,阻碍了该类气藏的勘探开发进程。川西坳陷须家河组储层为典型的致密砂岩储层,但在致密背景下发育相对优质储层,这些相对优质储层有较高的孔隙度和渗透率,对气井的高产发挥着重要的作用。在相对优质储层中有一种以绿泥石环边胶结发育为特征。文中通过大量镜下薄片鉴定、扫描电镜、X-衍射等手段,结合沉积相分析资料、区域地质及火山活动资料综合分析,确定了川西坳陷须家河组绿泥石形成的相对时期及其成因。研究认为,绿泥石主要是对原生孔隙起到了良好的保护作用,并且不是存在绿泥石环边胶结的砂岩储层均能成为相对优质的储层,其必须满足环边厚度足够并连续的条件、而且储层必须发育在高能的沉积环境之中。

Tight gas production is taking up bigger and bigger shares in China’s total natural gas production.However,further exploration and development of this kind of gas reservoirs face great challenges due to their distribution complexity and prediction difficulty.Although the Xujiahe Formation in western Sichuan depression is typical tight sandstone,it has relatively good reservoirs with relatively higher permeability and porosity.Research of these reservoirs reveals a unique phenomenon of the existence of a rim chlorite cementation.Based on analysis of data such as thin section,SEM and X-ray diffraction and in combination with sedimentary facies,regional geology and volcanic activity,the authors determined the period in which the chlorite was formed.It is suggested that the existence of chlorite can effectively protect the primary pores in these reservoirs.However,the sole exis-tence of ring-shaped chlorite cementation does not necessarily mean a relatively better reservoir.Other pre-requirements for a high-quality reservoir are also needed,for example,the ring must be thick and continuous enough and the reservoirs must be formed in high-energy sedimentary environment.

10.11743/ogg20120512