Fluid Inclusion Characteristics and Hydrocarbon Accumulation Significance of Shanxi Formation in Daning-Jixian Area

In order to clarify the gas accumulation process of Upper Paleozoic in Daning-Jixian area, the fluid inclusions in the study area were tested and analyzed comprehensively by single polarizing microscope observation, laser Raman spectroscopy analysis and microthermometry. Finally, the accumulation period was determined based on burial history. The results show that there are five types related to hydrocarbon accumulation in the study area, and the hydrocarbon inclusions mainly include the following four types: 1) methane inclusions; 2) asphalt-containing methane inclusions; 3) asphaltene inclusion; 4) methane inclusions containing CO2. The inclusions are mainly distributed in the healed microcracks, quartz edge enlarging and cracks, and the hydrocarbon inclusions are mainly distributed in the healed microcracks. Combined with the homogenization temperature of inclusions and the recovery results of thermal evolution history, the first stage was the kerogen cracking gas stage, and the homogenization temperature range of associated brine inclusions was 100°C - 170°C, and the main charging time was estimated to be 120 - 205 Ma. In addition, according to the characteristic peaks of a large number of asphaltene inclusions (or asphaltene-containing methane inclusions) in Raman test results, it is speculated that there is a second accumulation stage, namely the cracking stage of wet gas and condensate oil. Combined with the measured organic matter Ro > 2.0% in the study area, the corresponding time of the pyrolysis charging period was determined to be 100 - 120 Ma when projected into the thermal evolution history.