断陷盆地深层低渗透天然气储层孔隙演化定量研究

Quantitative Research for Porosity Evolution in Low Permeability Deep Gas Reservoir of Rift-Subsidence Basin

运用微观薄片、扫描电镜和微观图像等资料,以东营凹陷北部陡坡带深层砂砾岩体天然气储层为例,结合其储层温度与埋深资料,应用定量回推反演的方法对低渗透天然气储层孔隙演化进行了定量研究。根据储集空间类型和孔隙特征将储层划分为以次生溶蚀孔隙为主、次生孔隙与原生残余孔隙共存和以微裂缝为主3种类型。依据对储层物性的影响可以将成岩作用分为2大类:建设性的成岩作用类型(欠压实作用、溶解作用和重结晶作用)和破坏性的成岩作用类型(压实作用、沥青充填作用及各种胶结沉淀作用),并引入成岩作用强度的概念,定量分析了各类成岩作用对3种类型储层的孔隙演化的控制作用,认为Ⅰ型储层主要受酸性溶蚀作用影响,Ⅱ型储层由于上覆膏盐层的影响保留了一定量的原生孔隙,Ⅲ型储层早期压实强烈,后期酸性地层水很难进入,基本无溶蚀作用。

Based on data of micro-thin section,scanning electron microscope and image analysis,the porosity evolution of low permeability glutenite body as the deep gas reservoir in the northern slope of Dongying depression was quantitatively described by quantitative inversion,in combination with temperature and depth of reservoir.According to type of reservoir space and feature of pore,the reservoirs were divided into three types,i.e.secondary denudation pore type,coexistence type of secondary pore and primary remain pore,and micro-fissure type.Based on effect of physical properties of reservoir,two types of diagenesis were classified as constructive diagenesis（i.e.undercompaction,dissolution,recrystallization） and destructive one（compaction,bitumen filled and cementation deposit）.Then,we use the diagenesis intensity to quantitatively describe the controlling action of diagenesis to the porosity evolution of three types of reservoir.The Ⅰtype reservoir was mainly affected by acid dissolution.The Ⅱ type reservoir retained a certain amount of primary porosity due to gypsum-salt layer overlying.The Ⅲ type was almost not dissolved by later acid solution,because the early strong compaction existed so that the acid water can not come in.