高孔隙性岩石中变形带特征及对储层非均质性的影响

According to the differences in the microscopic deformation mechanism, Rocks can be divided into three types which include the high porosity (porosity is greater than 15%), low porosity (15%~5%) and the non-porosity (less than 5%). High porous rock deformation occurs mainly in disaggregation (consolidated and semi-consolidated), cataclasis (consolidated) and smear (clay content varies from 15% to 40%), these micro-structural types are generally called deformation band. Deformation band type depends on the host rock properties (porosity, clay content and mechanical properties), diagenesis degree, confining pressure(depth of deformation), temperature and stress mechanism, compared with the host rock, different deformation bands have different physical property ，and have different effects on reservoir heterogeneity. Quartz sandstone of the Changlongshan formation and lower Shihezi formations of LiuJiang basin in Qinhuangdao are analyzed for researching the geometric characters (appearance, length, thickness, displacement, spacing and combined pattern), Physical Properties (porosity and permeability), the classification of deformation band type (according to mechanical nature, according to deformation mechanism, physical properties, clay content and diagenesis degree, respectively) and the genetic mechanism of deformation bands， we will construct a geology model of reservoir and deformation bands to analyze the influence of different deformation bands on reservoir heterogeneity. It can solve the phenomenon that injection-production in oilfield and highly porous sandstone reservoir without oil in multilayer sandstone reservoir.

按微观变形机制差异可将岩石分为高孔隙性（孔隙度大于15%）、低孔隙性（15%~5%）和非孔隙性（小于5%）三种类型。高孔隙性岩石受力变形主要发生解聚（未固结-半固结）、碎裂（固结）和涂抹作用（泥质含量介于15%-40%），产生微构造类型统称为变形带。变形带类型取决于母岩性质（孔隙度、泥质含量和力学性质）、成岩程度、围压（变形深度）、温度和受力机制，同母岩相比，不同类型变形带物性差异较大，对储层非均质性有着不同的影响。本文以秦皇岛柳江盆地长龙山组和下石盒子组石英砂岩为研究对象，系统研究变形带的几何学特征（外观、长度、厚度、位移、间距和组合模式）、物性特征（孔隙度和渗透率）、类型（力学性质分类、变形机制分类、物性分类、泥质含量分类和成岩程度分类等）和成因机制，建立变形带和储层的地质模型，分析不同类型变形带对储层非均质性影响。以解决油田注采开发效果和多层砂岩储层中孔隙度较高砂岩储层不含油的现象。

该基金以准噶尔盆地南缘更新统-全新统砾岩、大庆长垣杏树岗构造过断裂取心井砂岩、冀中凹陷束鹿西斜坡过断裂取芯井砂岩以及秦皇岛鸡冠山海绿石石英砂岩中微构造为重点解剖对象，结合国外公开发表的文献成果，系统剖析了不同性质的砂岩断裂变形机制、微构造类型、特征及形成的断裂带内部结构，为深入研究砂岩内断裂封闭性具有重要的指导意义。研究表明，纯净的砂岩在未固结—半固结成岩阶段发生断裂，变形机制为颗粒边界摩擦滑动，导致颗粒旋转和滚动，即为颗粒流，形成的微构造为解聚带，孔渗性同母岩比没有明显降低。在固结成岩阶段（孔隙度大于15%）发生断裂，变形机制为碎裂作用，形成的微构造为碎裂带，渗透率同母岩比一般降低1～3个数量级。当温度超过90 ℃时，埋深大于3km，石英压溶胶结的速度明显增大，早期形成的解聚带和碎裂带均会因石英压溶胶结而增强封闭能力，形成压溶胶结碎裂带。不纯净的石英砂岩在未固结—固结成岩阶段发生断裂，断裂变形机制主要为层状硅酸盐与砂岩颗粒的混合作用，为封闭能力很强的变形带。不同类型变形带物性差异较大，对储层非均质性有着不同的影响。解聚带提高储层渗透率，碎裂带、压溶胶结碎裂带和层状硅酸盐带阻碍流体的流动。野外观察表明，流体不沿变形带流动，而是绕过变形带或沿着变形带周围的裂缝流动。这一认识解决了石油地质学中两个关键问题：一是断裂控制的多套储层往往存在含油气性差异，根本原因在于断裂在不同储层中伴生的微构造差异，母岩孔隙度越高，泥质含量越高，形成碎裂带、压溶胶结碎裂带和层状硅酸盐带物性越低，密度越大，油气越难以充注到储层中，导致并非物性好的储层都是油层。二是断层破碎带如果发育碎裂带、压溶胶结碎裂带和层状硅酸盐带，会导致储层极强非均质性，破碎带内富集的剩余油难以开采，利用多靶点定向井挖潜断层边部剩余油时，需要避开断层破碎带。