鄂尔多斯盆地马家沟组烃源岩有效排烃有机质丰度下限探讨——以龙探1井为例

Discussion on the Lower Limit of Organic Abundance of Effective Hydrocarbon Expulsion for the Source Rock from Majiagou Formation in Ordos Basin:Taking the Well Longtan 1 as an Example

烃源岩残余有机碳含量下限值是划分有效烃源岩的重要指标之一。目前关于碳酸盐岩有效烃源岩有机碳含量下限值主要由经验分析来确定,取值高低存在比较大的分歧。鄂尔多斯盆地马家沟组碳酸盐岩热演化程度高、有机质类型好。笔者针对马家沟组烃源岩生成油气具有近距离运聚的成藏特征,从烃源岩吸附气定量分析出发,结合典型井不同有机碳含量的烃源岩排烃史模拟计算,综合分析认为以0.25%作为高成熟—过成熟碳酸盐岩有效排烃的烃源岩残余有机碳含量下限值。

The lower limit of residual organic carbon is an important indicator to determine effective source rocks.At present,the lower limit of organic carbon content of effective carbonate source rock is mainly determined by empirical analysis and great differences exist.The carbonate of Majiagou Formation in Ordos Basin has high thermal maturity and good organic matter.According to the feature that the hydrocarbon generated by the source rock of Majiagou Formation migrated and accumulated in short distance,based on the quantitative analyses of source rock absorbed gas,combined with the simulated calculation of hydrocarbon expulsion of source rocks with different level of organic matter from typical wells,it is concluded that the lower limit of residual organic matter is 0.25% for the effective hydrocarbon expulsion of high-over mature carbonates.