深层储层原生孔隙成岩作用保存机制及模式——以珠江口盆地惠州凹陷南部恩平组和文昌组为例

Preservation mechanism and model of primary pore diagenesis in deep reservoirs:taking the Enping Formation and Wenchang Formation in the south of Huizhou Sag,Pearl River Mouth Basin as examples

为研究深层优质储层形成条件,以珠江口盆地惠州凹陷南部恩平组和文昌组为例,根据岩石薄片、阴极发光、扫描电镜、储层物性、埋藏史等资料,分析研究区储层特征,探讨深层储层原生孔隙成岩作用保存机制及模式。结果表明:惠州凹陷南部恩平组主要发育长石岩屑质石英砂岩,文昌组主要发育长石岩屑砂岩,孔隙类型以原生孔隙为主,孔隙度介于1.9%~17.3%,平均为13.3%;渗透率介于(0.034~152.683)×10^(-3)μm^(2),平均为18.050×10^(-3)μm^(2)。储层原生孔隙保存受多种因素控制,其中较低的地温梯度抑制压实作用,早期长时间浅埋藏和后期快速埋藏使压实作用不充分,碳酸盐差异胶结和早期油气充注阻碍压实和砂体中的胶结作用,导致储层原生孔隙普遍发育。该结果为建立深层勘探开发方案及优质储层平面和纵向分布预测提供依据。

In order to study the formation conditions of deep high-quality reservoirs,taking the Enping Formation and Wenchang Formation in the Southern Huizhou Sag of the Pearl River Mouth Basin as examples,the characteristics of the reservoirs in the study area were analyzed according to the data of rock thin section,cathodoluminescence,scanning electron microscope,reservoir physical properties,and burial history,then to discuss the preservation mechanism and model of primary pore diagenesis in deep reservoirs.The results show that feldspar lithic quartz sandstone is mainly developed in Enping Formation in the Southern Huizhou Sag,and feldspar lithic sandstone is mainly developed in the Wenchang Formation in the Southern Huizhou Sag.The pore types are mainly primary pores,and the porosity ranges from 1.9% to 17.3%,with an average of 13.3%,the permeability is between(0.034-152.683)×10^(-3)μm^(2),with an average of 18.050×10^(-3)μm^(2).The preservation of primary pores in the reservoir is controlled by many factors.Among them,the lower geothermal gradient inhibits the compaction,the long-term shallow burial in the early stage and the rapid burial in the later stage make the compaction insufficient,and the differential cementation of carbonate and the early oil and gas charging hinder the compaction and the formation of the reservoir.The cementation in the sand body leads to the widespread development of primary pores in the reservoir.The results provide a basis for establishing a deep exploration and development plan and predicting the horizontal and vertical distribution of high-quality reservoirs.