Microfracture development at Ziliujing lacustrine shale reservoir and its significance for shale-gas enrichment at Fuling in eastern Sichuan Basin, China

Abstract

Microfractures at the Ziliujing lacustrine shale at Fuling in eastern Sichuan Basin were investigated through core observation, SEM image observation and high-pressure mercury injection. and quantifies the impact of micro fracture development to reservoir capacity, leads to the following understanding: (1) fracture types in lacustrine shale reservoir are defined; (2) the contribution of fractures to lacustrine shale reservoir is determined. Results show that the microfractures in the Lower Jurassic Ziliujing lacustrine shale reservoirs in eastern Sichuan Basin can be divided into three types, each with four groups: micro fractures related to sedimentation (bedding fractures), microfractures related to diagenesis (clay–mineral shrinkage fractures), and micro fractures related to hydrocarbon generation (organic-matter shrinkage fractures and organic-matter-cracking fractures). High-pressure mercury injection and plane porosity determination confirm that microfractures in lacustrine shale reservoirs exhibit good reservoir performance, whose contribution to shale reservoir capacity is about 25%.