准噶尔盆地中部侏罗系三工河组储层沥青地球化学特征及其对油气成藏过程的指示

准噶尔盆地中部地区侏罗系三工河组储层中广泛发育固体沥青，记录了重要的油气成藏信息。基于岩相学、反射率、激光拉曼光谱和生物标志化合物等多方面的综合分析，结合构造和成藏演化史，探讨了沥青的成因、来源及其对油气成藏的指示意义。研究区三工河组储层沥青主要赋存在构造缝中，裂缝面存在弯曲变形，矿物显微构造变形明显，指示沥青形成与构造活动破坏古油藏有关。沥青的生物标志化合物特征与油源对比结果指示沥青主要来源于二叠系风城组和下乌尔禾组的烃源岩，具有混源成藏特征。沥青成熟度较低（等效镜质体反射率为0.62%～0.79%），且具强烈生物降解特征，说明为生物降解成因沥青，同时生物标志物指示沥青受到晚期原油充注的影响。古油藏成藏时间在中侏罗世车—莫古隆起形成初期，晚侏罗世—早白垩世古隆起抬升遭受强烈剥蚀，古油藏遭受破坏进而引发轻烃组分散逸，并伴随生物降解作用演化形成沥青。早白垩世，下乌尔禾组烃源岩晚期油气开始充注后，三工河组储层没有再发生强烈构造活动，随储层再次埋深和油气充注，最终形成现今油气藏。虽然研究区三工河组储层曾经历构造活动调整，但油气的再次充注使其仍成为有利的勘探对象。 

Geochemical characteristics of solid bitumen in the Jurassic Sangonghe Formation in the central Junggar Basin and its implications for hydrocarbon accumulation process

The ubiquitously distributed solid bitumen in the Jurassic Sangonghe Formation reservoir in the central Junggar Basin recorded the important information of hydrocarbon accumulation. In this study, based on lithology, reflectance of bitumen, laser Raman spectroscopy and biomarkers of bitumen, combined with the history of structure evolution and hydrocarbon accumulation, we studied the genesis of the reservoir bitumen and its indication for oil and gas accumulation. Results indicated that these solid bitumen were mainly distributed in structural fractures, the crack surface of the samples have experienced bending deformation, combined with obvious deformation of mineral microstructure. Solid bitumen was then indicated to be derived from the crude oil evolution after the destruction of the ancient reservoir due to tectonic activities. According to the parameter characteristics of biomarkers of bitumen, the crude oil was mainly derived from the source rocks of the Permian Fengcheng Formation and the Lower Wuerhe Formation. Therefore, the Sangonghe Formation reservoir has multi-source charging features. Due to the low maturity (equivalent vitrinite reflectance:0.62%-0.79%) of bitumen and the evidence for biodegradation, we concluded that the bitumen was generated by biodegradation. Whereas the biomarker showed that the bitumen was affected by the late oil accumulation. In conclusion, the ancient oil reservoirs were formed during the early stage of the formation of Che-Mo ancient uplift in the Middle Jurassic, and were destroyed during the Late Jurassic to the Early Cretaceous. Light hydrocarbon components were dissipated because of the reservoir destruction, then bitumen was formed due to the biodegradation. In the Early Cretaceous, there was no strong tectonic activity in the Sangonghe reservoir after the late hydrocarbon accumulation from the Lower Wuerhe Formation. With the reburial of the reservoir and hydrocarbon accumulation, the hydrocarbon reservoirs today were formed. Although the reservoir of the Sangonghe Formation has undergone tectonic activity adjustment in the study area, the recharge of oil and gas makes it still a favorable exploration target.