生烃潜力法在深层页岩气资源评价中的应用——以四川盆地五峰—龙马溪组优质烃源岩为例

Application of hydrocarbon generation potential method to deep shale gas resource evaluation: A case study of high-quality source rocks of the Wufeng-Longmaxi formation in the Sichuan Basin

为了深入认识和评价深层页岩气资源潜力,以四川盆地五峰—龙马溪组优质烃源岩为例,采用生烃潜力法对深层页岩气资源潜力进行评价.基于五峰—龙马溪组优质烃源岩的基本地质特征分析,建立该套烃源岩的生排烃模式,恢复并定量表征其生烃、排烃及残留烃过程,进而计算得到页岩气地质资源量,认为生烃潜力法在深层页岩气资源评价中具有良好的应用效果.研究结果表明:五峰—龙马溪组优质烃源岩分布面积广,厚度大,有机质丰度高,干酪根类型以Ⅰ型为主,处于高—过成熟演化阶段;五峰—龙马溪组优质烃源岩在等效镜质体反射率R_(o)为0.5%和0.7%时分别进入生烃门限和排烃门限,截至现今累计生烃量达1.36×10^(12) t,累计排烃量达1.12×10^(12) t,累计残留烃量为528×10^(8) t;五峰—龙马溪组优质烃源岩的页岩气地质资源量为25.69×10^(12) m^(3),可采资源量为4.78×10^(12) m^(3).综合评价分析认为,四川盆地五峰—龙马溪组优质烃源岩具有巨大的页岩气资源潜力,是四川盆地深层页岩气勘探开发的主战场.

To deeply understand and evaluate the resource potential of deep shale gas,samples from the high-quality source rocks of the Wufeng-Longmaxi formation in the Sichuan Basin were used to evaluate the resource potential of deep shale gas by the hydrocarbon generation potential method.Based on the analysis of the basic geological characteristics of high-quality source rocks in the Wufeng-Longmaxi formation,the hydrocarbon generation and expulsion model of the source rocks was established.And the hydrocarbon generation,expulsion,and residual hydrocarbon processes were recovered and quantitatively characterized.Then the geo-logical resources of shale gas were calculated.It is considered that the hydrocarbon generation potential method has good application to deep shale gas resource evaluation.The results show that the high-quality source rocks of the Wufeng-Longmaxi formation are widely distributed,thick,rich in organic matter with type I kerogen,and over matured.The source rocks reach the hydrocarbon generation threshold and hydrocarbon expulsion threshold at 0.5% R_(o) and 0.7% R_(o),respectively.Up to now,the cumulative hydrocarbon generation amount is 1.36×10^(12) t,the cumulative hydrocarbon expulsion amount is 1.12×10^(12) t,and the cumulative resid-ual hydrocarbon amount is 528×10^(8) t.The shale gas geological resources and technically re-coverable resources of high-quality source rocks in the Wufeng-Longmaxi formation are 25.69×10^(12) and 4.78×10^(12) m^(3),respectively.Comprehensive evaluation and analysis suggests that the high-quality source rocks of the Wufeng-Longmaxi formation have great shale gas resource potential and are the main battlefield of deep shale gas exploration and development in the Si-chuan Basin.