海拉尔盆地侏罗系烃源岩特征及发育模式——以红旗凹陷为例

Characteristics and Development Model of Jurassic Source Rocks of Hailar Basin:Case Study in Hongqi Sag

为了揭示海拉尔盆地红旗凹陷上侏罗统塔木兰沟组深层油气勘探前景并获取进一步的勘探突破,采用地质、地球化学方法对塔木兰沟组烃源岩发育特征及模式进行了分析。结果显示:塔木兰沟组为火山岩、沉积岩互层发育的成盆初期建造,其中塔四段滨浅湖—半深湖相暗色泥岩发育,表现为低声波、高伽马、高电阻的电性特征,地震上呈强振幅、层状-似层状反射。烃源岩有机质丰度中等,w(TOC)为0.07%~2.20%,平均为0.99%;Ⅱ型和Ⅲ型有机质均有发育,生源为藻类等水生生物和高等植物混合输入;有机质镜质体反射率值为0.90%~2.04%,整体为成熟—高成熟,局部受火山作用达到过成熟。该套烃源岩于早白垩世进入生油门限,对应埋深1450 m,现今正处于生烃高峰期,有效烃源岩面积329 km^(2),舒特诺尔次凹是主要的生烃中心,采用体积法估算生烃量为4.59×10^(8)t,排烃量为2.79×10^(8)t,资源量为0.64×10^(8)t,显示出较好的勘探潜力。烃源岩具有断陷初期填平补齐、气候温暖潮湿、有机质混源输入、微咸水弱氧化—弱还原环境、火山活动间接影响的发育模式。

In order to make a great breakthrough in the Upper Jurassic Tamulangou Formation in Hongqi sag of the Hailar basin,the characteristics and development model of Tamulangou Formation were analyzed by means of geology and geochemistry methods.The results show that the Tamulangou Formation is the initial basin formation with the development of volcanic rock and sedimentary rock interbedding.Among them,the main source rocks are the dark mudstone of the second member developed in the shore shallow lake and semi deep lake facies.The organic matter abundance is medium,the TOC content ranges from 0.07%to 2.20%with an average of 0.99%.Kerogens are both type II and type III,the precursors of source rocks are the mixed inputs of aquatic organisms such as algae and higher plants.The Rranges from 0.90%to 2.04%,with overall maturity-high maturity partially due to volcanic activity.The recovery results of hydrocarbon generation history indicate that the source rocks entered the oil generation threshold in the Early Cretaceous,corresponding to the buried depth of 1450 m,and now it is in the peak period of hydrocarbon generation.The effective source rock area is 329 km^(2),and the Shutner sub-sag is the main hydrocarbon generation center.The amount of hydrocarbon generation is 4.59×10^(8)t,the expulsion amount is 2.79×10^(8)t,and the resource amount is 0.64×10^(8)t,showing good hydrocarbon generation potential.The development of source rocks is characterized by structural deposition-controlled distribution,guaranteed by paleo-environmental conditions,dominant organic matter input capability,and volcanic activity-promoted evolution.In summary,it has a development model of“filling up in the early stage of fault depression in warm and humid climate,mixed source inputs of organic matter,under weak oxidation-reduction environment in brackish water,and indirect impact of volcanic activity”.The understanding has certain reference significance for the transformation of oil and gas exploration deployment to deep strata in the basin.