Three-stage hydrocarbon accumulations in the Middle Permian in the Central Sichuan Basin

作者：Jianyong Zhang, Yun Liao, Pengda Lu, Wenzheng Li, Kedan Zhu, Zeqi Li, T. Tian, Juan Wu, Wei Sun, Shugen Liu, Bin Deng · 发表于：Frontiers in Earth Science · 年份：2024 · DOI：10.3389/feart.2024.1369986 · 被引用次数：3 · 研究领域：Hydrocarbon exploration and reservoir analysis、Paleontology and Stratigraphy of Fossils、Geological and Geochemical Analysis

The Middle Permain Maokou Formation (P 2 m ) is a new region of natural gas exploration in the Sichuan Basin, is characterized by bioclastic limestone with localized dolomitization, and karst fractured-vuggy reservoirs. Currently, on the gas source, hydrocarbon accumulation process and control factors in the Sichuan Basin during the Permian are lacking. To bridge this gap, herein, we identified the filling sequence minerals inside the pores/vugs, along with the oil charge of the Maokou Formation using drill cores, thin sections, oil inclusion analysis, and U-Pb dating of calcite cements. The results showed that the reservoir space of the Maokou Formation was predominated by the residual dissolved pores/vugs, fractures, and dissolved fractures. The pores/vugs underwent four stages of mineral filling by very fine-fine (-crystalline, CC1) calcite → fine-medium calcite (CC2: from 256.4 ± 1.7 to 244.1 ± 6.3 Ma) → fibrous calcite (FC; ∼183.9 ± 8.2 Ma) → coarse-macro calcite (CC3; ∼171.5 ± 5.3 Ma). Combined with the homogenization temperature and salty of fluid inclusion, we considered that three stages of oil charge were present in the Maokou Formation reservoirs. The first stage involved the formation of paleo-oil reservoirs during the Late Permian to Early Triassic, corresponding to the high-maturity aqueous inclusions in CC2, with a homogenization temperature of 106.7°C–137.8°C. At that time, the oil generation from the Lower Cambrian Qiongzhusi Formation rocks peaked, and the g...