烃源岩生烃期次与油气成藏——以鄂尔多斯盆地西缘马家滩地区长7烃源岩为例

通过恢复鄂尔多斯盆地西缘马家滩地区长7烃源岩在不同构造热演化阶段的原始成熟度，研究其生烃期次及油气成藏特征。研究表明，长7烃源岩发生过3次生烃作用，第1次生烃作用发生在晚侏罗世．长7烃源岩Ro值为0．71％．进入大量生油阶段，但晚侏罗世晚期构造抬升作用使这次生烃产物破坏殆尽；第2次生烃作用发生在早白垩世，长7烃源岩R0值达0．89％，进入生油高峰阶段，是本区最重要的一次生油作用和成藏过程，与这次成藏事件相关的推覆构造圈闭是本区三叠系油气藏勘探的重点；古近纪晚期以来长，烃源岩由于喜马拉雅期构造运动而再次深埋藏，马家滩断褶构造带存在第3次生油和晚期成藏的良好条件，与晚期断裂构造有关的复合油气藏是值得重视的勘探目标。图5表2参26

Hydrocarbon generation and reservoir formation: A case from Chang 7 source rock in Majiatan area, west margin of Ordos Basin

By recovering the initial maturity of Chang 7 source rocks in Majiatan area in different structural thermal evolution periods, the hydrocarbon generation stages and reservoir formation features are studied. Chang 7 source rocks experienced 3 times of hydrocarbon generation. The first hydrocarbon generation took place at Late Jurassic with the maturity (Ro) of Chang 7 source rocks being 0.71%, entering the large-scale hydrocarbon-generation stage. But the oil produced during the stage escaped completely because of tectonic uplift in later Late Jurassic. The second hydrocarbon generation took place at Early Cretaceous with the Chang 7 source rocks maturity being 0.89%, entering the hydrocarbon-generation peak stage. This is the most important process for hydrocarbon generation and reservoir formation. The nappe structural traps related to this process are the main targets for hydrocarbon exploration in the study area. The Chang 7 source rocks were buried deeper because of Himalayan movement after late Paleogene. There are good geologic conditions for third-time hydrocarbon generation and reservoir formation in the Majiatan fault fold zone. The combination hydrocarbon reservoirs related to later fault structures are the valuable targets for exploration.