Abstract:

The study of shale reservoir space is one of the core contents of the shale oil and gas, and the shale pores have a great influence on the reservoir capacity and the percolation feature of the reservoir. Microscopic analyses of thin sections, scanning electron microscopy, focused ion beam milling(FIB), field emission SEM (FE - SEM) and Energy Dispersive Spectrometer (EDS) were used to determine the genesis, size, morphology, distribution, connectivity of the Longmaxi shale reservoir in the study area. Based on the genesis of reservoir space and the developing positions of the pores, the classification for the reservoir space was analyzed. The reservoir spaces of Longmaxi shale in the study area are divided into inorganic pores, organic pores and fractures. According to the diagenesis process of the shale, mechanical compaction, thermal evolution mechanism, clay mineral transformation, dissolution were considered to qualitatively discuss the formation and evolution process of the reservoir spaces. The reservoir spaces of the Longmaxi shale in the study area mainly include pores between clay mineral platelets, clay floc pores, pores within organic matter and fractures. Organic matter pores are the products of shale evolution to a certain stage, and not all the shale reservoir develop organic matter nanometer pores. The formation and preservation of organic matter nanometer pores are influenced by various factors.

Key words: shale reservoir, pore classification, nano pores, fracture, evolution of pores