准噶尔盆地东北缘石炭系烃源岩生烃演化特征及其石油地质意义

Hydrocarbon generation and evolution characteristics of Carboniferous source rocks on the northeastern margin of the Junggar Basin and its petroleum geological significance

准噶尔盆地东北缘石炭纪沟弧盆环境发育多种类型的烃源岩,为落实主力烃源岩高效供烃区,指导该区油气勘探,基于钻井、露头烃源岩样品有机地球化学及生烃热模拟实验等测试数据,地质—地化相结合,对不同类型烃源岩生烃机制、生烃潜力、生烃演化过程及供烃特征进行了研究。研究区石炭系主要发育泥岩、凝灰质泥岩和碳质泥岩3种类型的烃源岩;不同类型的烃源岩生烃母质构成、生烃活化能分布不同,其生烃潜力及生烃演化模式存在明显差异,即泥岩相对低成熟演化阶段快速生烃,凝灰质泥岩持续缓慢生烃,碳质泥岩相对高成熟演化阶段快速生烃;后期构造改造、沉积充填及地温场演化联合控制了烃源岩生烃热演化过程及供烃特征。依据烃源岩生烃与油气散失时空耦合,划分出高效生烃—低散失—高效供烃、高效生烃—较高散失—较高效供烃、较高效生烃—低散失—较高效供烃、较高效生烃—高散失—低效供烃、低效生烃—高散失—低效供烃和低效生烃—低散失—低效供烃6种供烃模式。石北、滴水泉等凹陷属较高效生烃—低散失—较高效供烃单元,具备形成大中型油气田的物质基础,为最有利的勘探区。

Various types of source rocks were developed in the Carboniferous trench⁃arc basin environment on the northeastern margin of the Junggar Basin.In order to implement the efficient hydrocarbon supply area of the main source rocks and guide the oil and gas exploration in this area,researches on the hydrocarbon generation mecha⁃nism,potential,evolution process,and hydrocarbon supply characteristics of different types of source rocks were carried out through the combination of geology and geochemistry based on the test data of drilling,organic geochemistry of outcrop source rock samples,and hydrocarbon⁃generating thermal simulation experiments.The results show that there are three types of source rocks,namely mudstone,tuffaceous mudstone and carbonaceous mudstone in the Carboniferous in the study area.Different source rocks have different parent material composition and activation energy distribution for hydrocarbon generation,and their hydrocarbon generation potential and evolution model have obvious differences.Mudstone generated hydrocarbon rapidly at relatively low maturity stage,tuffaceous mudstone continued to generate hydrocarbon slowly,and carbonaceous mudstone generated hydrocarbon rapidly at relatively higher maturity stage.Later structural transformation,sedimentary filling and geothermal field evolution jointly controlled the thermal evolution process and hydrocarbon supply characteristics of source rocks.Hydrocarbon generation and hydrocarbon loss of source rocks were coupled in time and space,and six hydrocarbon supply models can be divided,i.e.,(1)high⁃efficiency hydrocarbon generation,low hydrocarbon loss,high⁃efficiency hydrocarbon supply,(2)high⁃efficiency hydrocarbon generation,relatively high hydrocarbon loss,relatively high⁃efficiency hydrocarbon supply,(3)relatively high⁃efficiency hydrocarbon generation,low hydrocarbon loss,relatively high⁃efficiency hydrocarbon supply,(4)relatively high⁃efficiency hydrocarbon generation,high hydrocarbon loss,low⁃efficiency hydrocarbon supply,(5)low⁃efficiency hydrocarbon generation,high hydrocarbon loss,relatively low⁃efficiency hydrocarbon supply,and(6)low⁃efficiency hydro⁃carbon generation,low hydrocarbon loss,low⁃efficiency hydrocarbon supply.Among them,the Shibei and Dishuiquan sags are relatively high⁃efficiency hydrocarbon generation,low hydrocarbon loss and relatively high⁃efficiency hydrocarbon supply units with material foundation for forming large and medium⁃sized oil and gas fields,which are the most favorable exploration targets at present.