Figure 1. Development of shale nanopores under different hydrocarbon expulsion efficiencies
Figure 2. Contrast of shale nanopores under different pressures
In the lower Paleozoic of southern China, two sets of organic-rich marine shale with broad shale gas exploration and development potential are widely developed in the Lower Silurian and Upper Cambrian. At present, shale gas exploration in Fuling, Sichuan Basin, , Weiyuan - Changning and other areas of the Lower Silurian shale made a breakthrough to obtain industrial shale gas production capacity; However, the prediction of the potential resource of the Lower Cambrian shale has not yet obtained industrial capacity.Compared to the next Silurushi page During the Lower Cambrian shales, the hydrocarbon expulsion process experienced a higher degree of hydrocarbon expulsion process, resulting in a lower level of solid bitumen in the high evolution stage, while solid bitumen was important for the development of organic porosity of shale in the high evolution stage Therefore, the difference of hydrocarbon expulsion efficiency during shale oil formation may be the important reason for the favorable gas-bearing properties of these two sets of shales.In addition, the Lower Paleozoic shale in the south experienced complicated geological history Tectonic movement, burial depth is generally greater than 7 km, changes in formation pressure conditions will inevitably affect the original shale porosity system.
Xiong Yongqiang team of the State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, explored the influence of hydrocarbon expulsion efficiency and pressure on the development of high-mature shale nanopores through high-temperature and high-pressure thermal simulation and low-pressure CO2-N2 gas adsorption The research shows that the efficiency of hydrocarbon expulsion has an important influence on the micropore (pore size less than 2nm) and small mesopore (pore size 2-10nm) in shale with high evolution stage. However, for the development of nanopores with pore size larger than 10nm Without significant effect (Figure 1) .When the shale undergoes a higher degree of hydrocarbon expulsion during the oil production window, that is, the organic matter that accounts for 60% of its TOC content will lose 52% -72% (Pore size less than 10 nm). In addition, higher pressures favor the development of micropores (less than 2 nm in pore size) and small mesopores (2-10 nm in pore size) in shale (Figure 2).
The research was jointly funded by the National Natural Science Foundation of China and the strategic pilot science and technology project of the Chinese Academy of Sciences. The related achievements were published in Marine and Petroleum Geology.
