确定烃源岩有效排烃总有机碳阈值的方法及应用

针对油气地质学中排烃源岩难以识别的问题，依据生排烃原理，利用常规烃源岩有机碳和热解（Rock-Eval）分析测试参数，建立了判别排烃源岩的实用方法。该方法主要基于生烃量参数I_HC=S₁/w（TOC）]和沥青转化率w（A）/w（TOC）]，判别排烃源岩的总有机碳阈值，高于该值的烃源岩即为排烃源岩。根据分析测试资料，对准噶尔盆地和三塘湖盆地二叠系芦草沟组、酒泉盆地营尔凹陷和青西凹陷白垩系下沟组以及鄂尔多斯盆地上三叠统延长组长7段的排烃源岩进行判别，判别效果较好，应用该方法时要求烃源岩的母质特征与热演化程度接近。由于气态烃易散失，所以采用的参数主要反映烃源岩中生成的液态烃量。该方法对于油源岩的判别更为有效。

Method and application for identifying TOC threshold of hydrocarbon-expelling source rocks

Considering the fact that hydrocarbon-expelling source rocks are difficult to identify in oil and gas geology, a method to distinguish hydrocarbon-expelling source rocks was proposed using the conventional TOC and pyrolysis analysis parameters (Rock-Eval). This method is used to identify the TOC threshold, based on hydrocarbon-generation amount parameters I_HC=S₁/w(TOC)] and w(A)/w(TOC)]. Only when TOC content is higher than the threshold, can the source rock be regarded as hydrocarbon-expelling source rock. This method was applied to the source rocks in the Permian Lucaogou Formation in the Junggar and Santanghu basins, the Cretaceous Xiagou Formation in the Ying'er and Qingxi sags in the Jiuquan Basin, and the Upper Triassic Yanchang Formation Chang-7 member in the Ordos Basin. The discriminant results are useful, but it requires source rocks with similar organic matter type and maturity. The parameters represent liquid hydrocarbon amount. Gaseous hydrocarbons are lost easily, and as a result, the method is more effective for oil source rock.