歧口凹陷沙三段烃源岩评价及生排烃特征

Source rock evaluation and hydrocarbon generation and expulsion characteristics in Es_(3) in Qikou Sag

以桂源岩热解分析数据为基础,结合PetroMod盆地模拟技术,明确研究区痊源岩特征及热演化史,运用生桂潜力法建立生排痊模式,分析生排痊史及排痊强度,揭示歧口凹陷沙三段痊源岩热演化与生排痊作用对油气运聚与分布的影响。结果表明:研究区痊源岩普遍处于成熟-高成熟演化阶段,在镜质组反射率约为0.53%和0.83%时分别进入生坯和排痊门限,其排痊率达250mg/g,排痊效率达65%。晚始新世末一早渐新世开始短暂生痊,因构造抬升运动而中止,在中渐新世开始排坯,至中渐新世末达到生排桂高峰期,之后于晚渐新世末再次因构造运动生排疑中止,整个生排坯过程与桂源岩热演化阶段基本一致。排坯中心沿歧北次凹一歧口主凹周缘分布,排妊强度达90x10^(6)t/km^(2),具有强排妊特征。广泛式的生排分布特征为歧口凹陷邻近隆起和斜坡部位提供了丰富的油气来源和运移动力,油气同时具有近源成藏及远距离侧向运移成藏的特征。

The characteristics and thermal evolutionhistory ofsource rocks in the study area are clarifiedbased on thepyrolysis analysis data ofsource rocks and PetroMod basin simulation technology.The hydrocarbon generation and expul­sion modes are constructed by the hydrocarbon generation potential method to analyze the hydrocarbon generation and expulsionhistory and intensity.As a result,the influence ofthennal evolution and hydrocarbon generation and expulsion ofsource rocks on oil and gas migration,accumulation,and distributionis revealed in the 3rd Member ofEocene Shahejie Formation(Es_(3))in Qikou Sag.The results show that the source rocks in the study area are generally in mature to highly mature evolution stages.The source rocks enter the hydrocarbon generation and expulsion threshold respectively when the vitrinite reflectance is about 0.53%and 0.83%.The hydrocarbon expulsionrate is 250 mg/g and the hydrocarbon ex­pulsion efficiency is 65%.Hydrocarbon generation began briefly at the end ofthe late Eocene and stopped due to tecton­ic uplift in the early Oligocene.Hydrocarbon expulsion began in the middle Oligocene and reached the peak ofhydrocar­bon generation and expulsion at the end ofthe middle Oligocene.The consequent hydrocarbon generation and expulsion stopped again due to the tectonic movement at the end ofthe late Oligocene,and the whole hydrocarbon generation and expulsion process is basically consistent with the thermal evolution stage of source rocks.The hydrocarbon expulsion center is distributed along the periphery of Qibei Subsag to Qikou main sag,and the hydrocarbon expulsion intensity is up to 90x10^(6)t/km^(2) with strong hydrocarbon expulsion characteristics.The extensive hydrocarbon generation and expul­sion distribution characteristics provide rich oil and gas sources and migration power for the adjacent uplift and slope of Qikou Sag.Additionally,the hydrocarbon has the characteristics ofnear sourcereservoir formation and long-distance lat­eral migration reservoir formation.