川南赤水地区天然气成因多样性分析

Natural Gas Genesis Diversity of Chishui in the Southern Sichuan

针对川南赤水地区天然气来源不明的问题,利用天然气组分、烷烃碳氢同位素、天然气轻烃等地球化学特征,结合地质特征,分析川南赤水地区不同层系天然气的成因类型与气源。研究表明,川南赤水地区以烃类气为主,除侏罗系天然气干燥系数相对较低外,其他层系为典型干气,且不同层系天然气成因具有多样性:研究区陆相侏罗系表现出煤型气的特点,主要来源于须家河组煤系烃源岩;须家河组气藏为混源气,既有海相偏腐泥型气,又有陆相煤型气,主要来源于须家河组和二叠系烃源岩;海相雷口坡组虽有混源特征,但以海相偏腐泥型气为主,而嘉陵江组、茅口组以海相偏腐泥型气为主,气源为二叠系与志留系烃源岩。该研究解决了川南地区气源问题,可为下步勘探部署提供依据。

Natural gas composition,alkane hydrocarbon isotopes,natural gas light hydrocarbons and other geochemical properties were used to analyze the natural gas genesis category and gas sources of different stratum series in Chishui of southern Sichuan by combining with geological properties. Research indicates that the natural gas in Chishui of southern Sichuan is dominated by hydrocarbon gas. In addition to the Jurassic natural gas with relatively low dry coefficient,the natural gases in other stratum series are all considered as typical dry gas with diverse geneses.The continental Jurassic natural gas in the study area is similar to that of coal-type gas and mainly migrates from the coal-measure source rock of Xujiahe Formation. The natural gas in the Xujiahe Formation is a mixed-source gas,including marine partial sapropel gas and continental coal-type gas,which mainly migrate from the Xujiahe Formation and Permian source rocks. The natural gas with mixed-source indication in the marine Leikoupo Formation is dominated by partial sapropel gas. The natural gas in the Jialingjiang Formation is dominated by marine partial sapropel gas,and the gas migrates from the Permian and Silurian source rocks. This research identifies the gas sources in southern Sichuan and could provide certain reference for the further hydrocarbon exploration and deployment.