川东H气藏沙溪庙组储层特征及物性主控因素

Reservoir Characteristics and Main Controlling Factors of Physical Properties of the Shaximiao Formation in the Chuandong H Gas Reservoir

摘要: 目的：针对川东H气藏沙溪庙组储层特征及物性主控因素不明确的问题。方法：综合运用岩心观察、薄片鉴定、压汞实验等多种分析方法，对H气藏沙溪庙组储层的岩石特征、储层孔隙、孔喉特征及孔隙度和渗透率的相关性进行分析和研究。结果表明：沙溪庙组储层主要由岩屑长石砂岩及长石岩屑砂岩组成，粒径以中粒为主，分选性较差，颗粒多呈次棱–次圆状；储集空间以次生溶孔和残余原生孔为主，孔喉半径小、突破压力高，喉道细小；孔隙度和渗透率呈明显的正相关性，属于特低孔–特低渗储层；沉积微相中分支河道、水下分支河道微相砂体的粒度较粗，分选较好，杂基含量低；有利于储层原始孔隙的保存和后期孔隙演化，优势沉积微相和成岩演化是沙溪庙组储层物性发育的主控因素。

Abstract: Objective: To address the unclear issues regarding the reservoir characteristics and main controlling factors of the physical properties of the Shaximiao Formation in the Chuandong H Gas Reservoir. Methods: A comprehensive analysis was conducted on the rock characteristics, reservoir pores, pore-throat features, and the correlation between porosity and permeability of the Shaximiao Formation reservoir in the H Gas Reservoir by integrating multiple analytical methods, including core observation, thin section identification, and mercury injection test. Results show that the Shaximiao Formation reservoir is mainly composed of lithic arkose and feldspathic litharenite, with medium grain size as the dominant fraction, poor sorting, and particles mostly subangular-subrounded in shape. The reservoir spaces are dominated by secondary dissolution pores and residual primary pores, characterized by a small pore-throat radius, high breakthrough pressure, and fine throats. Porosity and permeability exhibit a significant positive correlation, indicating an ultra-low porosity and ultra-low permeability reservoir. Among the sedimentary microfacies, the sand bodies of three microfacies (distributary channel, subaqueous distributary channel, and point bar) are characterized by coarser grain size, better sorting, and low matrix content, which are conducive to the preservation of original reservoir pores and the evolution of late-stage pores. Dominant sedimentary microfacies and diagenetic evolution are the main controlling factors for the development of physical properties of the Shaximiao Formation reservoir.