邻水–大竹地区长兴组储层特征及分类评价

Reservoir Characteristics and Classification Evaluation of the Changxing Formation in the Linshui-Dazhu Area

摘要: 本文基于岩心观察、薄片鉴定、物性测试及压汞资料，系统研究了四川盆地邻水–大竹地区二叠系长兴组碳酸盐岩储层特征，结果表明：储层岩性以白云岩和灰岩为主，其中晶粒白云岩、颗粒白云岩及生物礁白云岩为重要储集岩类；储集空间以孔隙型为主，裂缝与溶洞次之，组合类型多为裂缝–孔隙型；储层整体表现为低孔–低渗特征，孔隙度主要分布于2%~6%，渗透率多低于0.01 × 10⁻³ μm²；微观孔隙结构具粗孔粗喉与细孔微喉共存、孔喉连通性较好、分选中等–良好的特点；储层发育受沉积环境、成岩作用与构造活动共同控制，颗粒滩为优质储层发育的有利相带；综合评价将储层划分为III类为主、II类次之、I类极少，研究成果为该区下一步油气勘探与目标优选提供了地质依据。

Abstract: Based on core observation, thin section identification, physical property testing, and mercury intrusion porosimetry data, this study systematically investigates the reservoir characteristics of the Permian Changxing Formation carbonate rocks in the Linshui-Dazhu area of the Sichuan Basin. The results show that the reservoir lithology is mainly composed of dolomite and limestone, among which crystalline dolomite, granular dolomite, and reef dolomite are the major reservoir rock types. The reservoir space is dominated by pores, followed by fractures and vugs, with fracture-pore combinations being the most common type. Overall, the reservoirs exhibit low porosity and low permeability, with porosity values mainly ranging from 2% to 6% and permeability mostly below 0.01 × 10⁻³ μm². On the microscopic scale, the pore structure is characterized by the coexistence of coarse pores-throats and fine pores-microthroats, moderate to good sorting, and relatively good pore-throat connectivity. Reservoir development is jointly controlled by sedimentary environment, diagenesis, and tectonic activity, with the grain shoal facies being the most favorable zone for high-quality reservoir development. Comprehensive evaluation indicates that Class III reservoirs are dominant, followed by Class II, while Class I reservoirs are rare. Overall, the reservoirs show medium to poor storage capacity. The results of this study provide a geological basis for future hydrocarbon exploration and target optimization in the area.