关键词: 页岩气储层, 孔隙结构, 形状系数, 孔隙演化, 成岩作用

Abstract: The nanopore characteristics especially the pore morphology of Longmaxi and Qiongzhusi black shales of typical wells in Sichuan Basin and its periphery such as Well A to D were analyzed by Field emission scanning electron microscopy (FESEM), Pores and Cracks Analysis System (PCAS)—a SEM image processing software, and low-pressure N2 adsorption was used as a secondary tool. The form factor was the major parameter to characterize the pore shapes in this study. The results show that the nanopore morphology of black shales are controlled by the nanopore type (occurrence location of nanopores), maceral type, burial depth, thermal maturity of organic matters and the pore sizes. Here are the details: (1) The ratios, pore sizes, form factors of interparticle pores, intraparticle pores and organic matter pores are quite different, which shows that the evolution of the three types of nanopores have different paths. (2) The pore shapes of nanopores in solid bitumen are more regular than those in other macerals. (3) The compaction related to the burial depth can compress the pores vertically, to reduce the pore sizes and change the pore shapes from round or elliptical-shaped to slit-shaped. (4) The nanopores shapes of organic matter pores generally tend to be more regular with the increase of thermal maturity, although the trend may be disrupted by the compaction and the merging of nanopores. (5) The nanopores that have smaller sizes tend to have more regular pore shapes. The preliminary study shows that the morphology of nanopores in solid bitumen may indicute the pressure environment of main reservoir space in the high-over mature shale gas reservoirs. However, the pattern of the pore morphology evolution
in solid bitumen，and the possibility of using form factor of nanopores in solid bitumen to evaluate the overpressure and shale gas preservation condition in potential gas shales still need further research.