四川盆地金秋气田：一个典型以中生界沉积岩为氦源岩的含氦-富氦气田

The Jinqiu gas field in the Sichuan Basin： A typical helium-bearing to helium-rich gas field with the Mesozoic sedimentary rocks as helium source rocks

张宝收 张本健 汪华 陈践发 刘凯旋 豆霜 戴鑫 陈双玲

Baoshou ZHANG Benjian ZHANG Hua WANG Jianfa CHEN Kaixuan LIU Shuang DOU Xin DAI Shuangling CHEN

氦气成藏长期以来研究较少，成藏条件与成藏机理还不十分清楚，氦源岩类型和形成条件争议较大。通过解剖含氦-富氦的金秋气田认为：①金秋气田氦气含量主要分布在0.05 %～0.10 %，平均为0.07 %，部分井含量超过0.10 %，最高为0.20 %。同位素分析认为氦气为壳源成因，没有幔源的贡献。②金秋气田是一个典型以中生界沉积岩为氦源岩的含氦-富氦气田。上三叠统须家河组和侏罗系具有较高的铀、钍元素含量和较大的地层厚度，在金秋地区具有较高的氦气生气强度，是形成含氦-富氦气藏的氦源基础。氦气应该主要来源于侏罗系储层，而非上三叠统须家河组烃源岩层系。③金秋气田含氦-富氦气田的形成受3个主要因素控制，具有高氦气生气强度的氦源岩提供了很好的物质基础；具有适度充注强度的烃类气体的存在有利于氦气富集；地层抬升剥蚀温、压下降导致的原位溶解氦气脱溶作用是氦气富集的有益补充。

The lack of studies over an extended period leads to an unclear understanding of helium accumulation conditions and mechanisms， along with fierce controversy over the types and formation conditions of helium source rocks. Focusing on the helium-bearing to helium-rich Jinqiu gas field， this study presents the following key findings through detailed analysis： （1） The Jinqiu gas field exhibits a helium content ranging from 0.05 % to 0.10 % primarily， with an average of 0.07 %. In some wells， the helium content exceeds 0.10 %， reaching a maximum of 0.20 %. Isotope analysis reveals that helium in the gas field originates from the crust， without any contribution from the mantle. （2） The Jinqiu gas field is identified as of a typical helium-bearing to helium-rich type with the Mesozoic sedimentary rocks serving as helium source rocks. Both the Upper Triassic Xujiahe Formation and the Jurassic strata demonstrate high uranium and thorium contents， along with considerable thickness. They exhibit a high helium-generating intensity in the Jinqiu area， serving as helium source rock basis for the formation of helium-bearing to helium-rich gas reservoirs. Helium is presumed to primarily originate from the Jurassic reservoirs rather than the hydrocarbon source rock sequence of the Upper Triassic Xujiahe Formation. （3） The formation of the Jinqiu gas field is primarily under three factors. First， helium source rocks with a high helium-generating intensity act as a sound material basis. Second， the presence of hydrocarbon gases with a moderate charging intensity contributes to helium enrichment. Last， the uplift and erosion of strata， accompanied by a decrease in temperature and pressure， result in the exsolution of in-situ dissolved helium， conducive to helium gas enrichment.

10.11743/ogg20240113