惠民凹陷沙河街组基山三角洲中孔低渗储层成岩作用和有利储层成因

Diagenesis of medium porosity and low permeability reservoir and genesis of favorable reservoir of Jishan delta of Shahejie Formation in Huimin Depression

惠民凹陷沙河街组基山三角洲砂体主要由长石砂岩和岩屑长石砂岩构成。该储层在成岩演化过程中,经历了压实、胶结、溶解和交代等成岩作用,现埋深1 600~3 500 m,处于中成岩演化阶段,总体为中孔、低渗储层。溶蚀作用对于改善储层物性起到了重要作用,尤其是在2 400~2 600 m深度段有机酸对长石颗粒的溶蚀所形成的粒间和粒内孔隙,使储层孔隙度和渗透率均得到了提高,从而改善了储层物性,其中孔隙度可达25%,渗透率可达50 mD。因此,溶蚀作用及由其产生的次生孔隙发育段对于有利储层的预测非常重要。

The sand bodies of Jishan delta of Shahejie Formation in Huimin Depression are consisted of feldspathic sandstone and lithic sandstone, mainly experienced compaction, cementation, dissolution and metasomatism in the burial diagenetic evolution, and the diagenetic evolution reached the middle diagenetic stage, which results in the medium porosity and low permeability reservoir（current burial depth 1 700-3 500 m）. The dissolution played a significant role in improving reservoir properties in the burial diagenetic evolution. The intergranular pores and intragranular pores, caused by the feldspar dissolution in the depth of 2 400-2 600 m, are constructive for the reservoir properties in increasing the porosity and permeability（the porosity up to 25% and the permeability up to 50 mD）. Obviously, the zone where the dissolution and the secondary pores developed is very important for predicting favorable reservoir.