Sequence of densification and hydrocarbon charging of Xu2 reservoir in Anyue-Hechuan area, Sichuan Basin, China

The sequence of the densification and hydrocarbon charging of the Xu2 reservoir in the Anyue–Hechuan area of Central Sichuan Basin is discussed. The diagenetic sequence is considered a time line to determine the historical relationship between the densification process and the hydrocarbon charging of the Xu2 reservoir in the study area：Early diagenetic stage B （the first stage of hydrocarbon charging, which was about 200–160 Ma ago, with a porosity of about 20%, consolidated and not tight） → middle diagenetic stage A （the second stage of hydrocarbon charging, which was about 140–120 Ma ago, with a porosity of 10%–20%and relatively tight） → middle diagenetic stage B （the third stage of hydrocarbon charging, which was about 20–5 Ma ago, with a porosity of 6%–10%and tight;However, fractures have developed）. The study results prove that large-scale hydrocarbon charging and accumulation completed before the densification of the Xu2 reservoir, showing that the Upper Triassic Xujiahe Fm unconventional tight reservoir in the Sichuan Basin is prospective for exploration.