Key indexes for hydrocarbon formation of tight sandstones and favorable areas of Baiguowan Formation in Xichang Basin

Based on existing drillings, a large number of outcrop profiles, and test data of samples, the indicators related to hydrocarbon formation such as hydrocarbon generation intensity,vitrinite reflectivity and sandstone reservoir of Baiguowan Formation in Xichang Basin are evaluated. The main hydrocarbon reservoir type of the Upper Triassic Baiguowan Formation in Xichang Basin is medium-coarse sandstones. The dessert sections are mainly the first, the third and the fourth Members of Baiguowan Formation. The sandstones have the characteristics of medium porosity, low permeability,wide regional distribution, and large thickness. The sandstones have good hydrocarbon properties in Well ZD-1. The source rocks of Baiguowan Formation in Xichang Basinare with a large thickness in the center and a thinning thickness in the edge. The hydrocarbon generation intensity is 56.74×10⁸m³/km² to 97.70×10⁸m³/km² in the basin center. The regional vitrinite reflectivity (R_O) is between 1.08% and 3.98%, which is lower in the eastern basin and higher in the western basin. The Jiatie-Sikai tight sandstone hydrocarbon favorable accumulation area and four dessert areas are comprehensively optimized. The hydrocarbon generation intensity is 10×10⁸m³/km²to 80×10⁸m³/km², the R_O is 1.08% to 3.0%, the thickness of medium-coarse sandstone is 10m to 50m, while the natural gas resource is 6756×10⁸m³, which can form the tight sandstone reservoir of "modification and reconstruction" type.