RESEARCH ON STRUCTURAL FEATURE CONTROL AND NANO-SCALE EVOLUTION PROCESS OF SLAB STRATA OF LONGMAXI FORMATION IN WEIYUAN GAS FIELD CHINA.

The pore characteristics of shale reservoir determine the shale gas content. This article uses three shale gas wells in Weiyuan area as the research object. Based on scanning electron microscopy and low-temperature liquid nitrogen adsorption experiments, the effect of shale lithofacies on the pore structure of the Wufeng-Longmaxi formation is studied by combining semi-quantitative and quantitative experiments. The results show that the shale of the LM1-LM3 interval in Weiyuan area located at the bottom of the Longmaxi Formation, is composed mainly of siliceous minerals, with high organic content. The LM4-LM8 interval located in the middle of the Longmaxi Formation has high content of clay minerals and carbonate minerals and low organic matter content. The shale pores in the LMl-LM3 interval are mainly provided by organic matter, and the shale pores in the LM4-LM5 interval are mainly provided by organic matter and clay minerals. Carbonate minerals have a certain contribution to the development of shale pores. The organic pores have relatively good homogeneity, which contributes the most to pores below lOnm. The internal pore development of carbonate minerals is highly heterogeneous, and the pore size is mainly distributed between 20 and 100 nm. The pores of clay minerals are highly heterogeneous, and the pore diameters are mainly distributed between 60 and 200 nm, which makes a great contribution to the pores of LM4-LM5 and LM6-LM8 formations. In the process of shale sedimentary diagenesis, fluid substances modify the soluble substances in the rock, providing space for the methane in the shale. [ABSTRACT FROM AUTHOR]