川中地区中二叠统气源新认识及成藏模式

New Insight for Gas Source and Gas Accumulation Modes of Middle Permian in Central Sichuan Basin

针对川中地区中二叠统气源复杂的问题,利用分区块研究和地球化学-地质研究相结合的思路,采用气-气、沥青-源岩对比方法,重点开展关于川中地区中二叠统的烃源条件解剖、天然气地球化学特征分析、气源综合对比,形成气源新认识。气源综合对比及地质研究表明,川中地区不同区块中二叠统气源各异,其中,高石梯-磨溪地区栖霞组天然气来源于筇竹寺组泥岩,志留系尖灭线以南的高石梯地区栖霞组天然气来源于龙马溪组泥岩,龙女寺-南充地区中二叠统天然气为筇竹寺组泥岩和下二叠统泥灰岩混源。在气源认识的基础上总结了川中地区中二叠统3种不同的成藏模式,其中,高石梯-磨溪地区发育下生上储成藏模式,志留系尖灭线以南的高石梯地区发育旁生侧储成藏模式,龙女寺-南充地区发育双源共储成藏模式。

In order to understand the complex gas source of Middle Permian in Central Sichuan Basin,the comprehensive study on the hydrocarbon source conditions,the geochemical characteristics of natural gas and the gas sources was carried out by gas-gas and bitu- men-source rock comparison. It is held that the Middle Permian gas source of different blocks in Central Sichuan Basin is different ： the Xixia Formation natural gas in Gaoshiti-Moxi area is from Qiongzhushi Formation mudstone, the Xixia Formation natural gas in the Gaoshiti area which is located in the south of Silurian extinction line is from Longmaxi Formation mudstone, and the Middle Permian natural gas in Longnvshi-Nanchong area is the mixture of the natural gas from Qiongzhushi Formation mudstone with from lower Permian marlite. Three hydrocarbon accumulation modes of Middle Permian in Central Sichuan Basin are summarized based on the understanding of gas source ：the accumulation mode of the Gaoshiti-Moxi area is ＂lower generation and upper storage＂ ,the accumulation mode of the Gaoshiti area in the south of Silurian extinction line is ＂side generation and side storage＂, and the accumulation mode of the Longnvshi- Nanchong area is ＂dual source co-storage＂.