长石溶蚀作用对储层物性的影响——以渤海湾盆地东营凹陷为例

Impact of feldspar dissolution on reservoir physical properties: a case from Dongying Sag,the Bohai Bay Basin

渤海湾盆地东营凹陷砂岩储层中长石含量丰富,而且长石溶蚀现象普遍,对储层物性具有重要影响。运用偏光显微镜、扫描电镜以及X-射线粉晶衍射等分析技术,对东营凹陷砂岩储层中长石及其溶蚀产物的分布特征进行了研究。结果表明:在不同地区长石含量存在差异,凹陷北部长石含量最高,其次是南部,最低的是中部地区;在层位上,沙河街组一段长石含量最高,其次为沙河街组二段和沙河街组四段,含量最低的是沙河街组三段;在东营凹陷砂岩储层中,长石主要的溶蚀产物为高岭石、伊利石和绿泥石。由于高岭石向伊利石和绿泥石转化,导致高岭石含量逐渐降低,浅部的伊利石和绿泥石主要由伊/蒙混层转化而来,而深部的伊利石和绿泥石主要由高岭石蚀变形成。砂岩储层中的伊/蒙混层矿物在浅层含量高,随着埋藏深度增加,含量逐渐降低。

Sandstone reservoirs in Dongying Sag, the Bohai Bay Basin are rich in feldspar, dissolution of which is very com- mon and has an important influence on reservoir physical properties. Polarizing microscope, SEM and X-ray powder diffrac- tion technologies were used to study the distribution characteristics of feldspar and its dissolution products in the sandstone reservoirs in Dongying sag. The content of feldspar varies in different areas. The highest content of feldspar occurs in the north,followed by the south, and the lowest is in the central area. Vertically, EsI is the richest in content of feldspar, fol- lowed by Es2 and Es4 f, and Es3 is lowest. The main dissolution products of feldspar in the sandstone reservoirs in Dongying sag include kaolinite,illite and chlorite. The transformation kaolinite to illite and chlorite causes the decrease of content of kaolinite. The illite and chlorite in the shallow layer are mainly transformed from I/S ,while they come from kaolinitic alter- ation in the deep layer. The content of I/S is high in shallow layer,and reduces with the increasing depth.