渤南油田中部古近系沙河街组低渗透储层岩石学和成岩作用

Petrology and diagenesis of the low permeable reservoir rocks from the Paleogene Shahejie Formation in central Bonan Oil Field, Shandong

该区储层岩石类型主要为岩屑质长石砂岩 ,溶解作用是主要的建设性成岩作用 ,压实、自生矿物充填和胶结作用是主要的破坏性成岩作用 ,成岩阶段处于晚成岩A亚期。该区储层较高的孔隙度是晚成岩期强烈的溶解作用形成次生溶孔的结果 ,而储层砂岩较低渗透率的主要成因机理是成岩期各种自生矿物的充填和胶结作用 ;此外 ,溶蚀作用形成的孤立、互不连通的粒间孔也是形成低渗微细喉道储层的主要原因。有利孔隙组合为粒间溶蚀孔 原生粒间孔 粒内破碎缝 ,有利储层的分布受砂体分布。

The Petrology and diagenesis of the low permeable reservoirs from the Paleogene Shahejie Formation in central Bonan Oil Field, Shandong are examined on the basis of drilling cores, thin sections, microprobe (analysis), scanning electron microscopy, cathodoluminescence and X-ray diffraction analysis. The reservoir rocks consist mostly of lithic arkose. The dissolution is believed to be a dominantly constructive diagenesis, whereas the compaction, filling and cementation of authigenic minerals are considered as a dominantly destructive diagenesis. The diagenesis may be ascribed to the A substage of the late diagenetic stages. The highly dissolution during the late diagenetic stages was responsible for the formation of the higher porosity of the reservoir rocks. The genetic mechanisms of the low porosity of the reservoir rocks include the compaction, filling and cementation of authigenic minerals during the late diagenetic stages. The isolated and disconnected interparticle porosities caused by the dissolution permitted the low permeable microthroats to be developed. The good porosity associations consist of interparticle porosity-primary interparticle porosity-intraparticle cracks. The distribution of the favourable reservoir rocks tends to be governed by sandstone distribution, structural arrangement and diagenesis.