渤中凹陷渤中A-2区新近系明化镇组岩性油气藏油气运移特征

Oil and gas migration characteristics of lithologic reservoirs of Neogene Minghuazhen F ormation in Bozhong A-2 area,Bozhong Sag

通过烃源岩特征分析及典型井原油样品的生物标志化合物参数对比,对渤中凹陷西南环带渤中A-2区新近系明下段岩性油气藏的原油来源及其运聚规律进行了研究。研究结果表明:(1)渤中凹陷西南环带纵向发育东三段、沙一段及沙三段等层段烃源岩,东三段烃源岩具C_(19)TT优势,Ts丰度值较大,C_(27)-C_(28)-C_(29)规则甾烷呈“V”形分布;沙一段烃源岩具C_(23)TT优势,Ts与Tm丰度值相近,γ蜡烷丰度值大,C_(27)-C_(28)-C_(29)规则甾烷呈“L”形分布;沙三段烃源岩具C_(21)TT或C_(23)TT优势,Ts丰度值较大,C_(27)-C_(28)-C_(29)规则甾烷呈“V”形分布,具C_(27)优势。(2)原油物性参数及气相色谱图差异性分析结果显示,渤中A-2油藏东南井区原油充注能力强于中部井区,C_(27)-C_(28)-C_(29)规则甾烷整体呈“L”形分布,4-甲基甾烷峰值较大。明下段上部原油C_(19)TT/C_(23)TT的值较小,MPI1和MPI2参数均较大,全油碳同位素稍重,显示其油源以沙一段供烃为主、沙三段供烃为辅。(3)渤中A-2油藏各井的1-甲基菲、9-甲基菲、C_(29)ααS/(S+R),C_(29)ββ/(αα+ββ)、二苯并噻吩系列、QGF指数等参数均呈规律性变化,指示了原油运移路径为经东南向西北运移聚集成藏。原油生物标志化合物对比结果显示,渤中凹陷西南环带深部原油先汇聚至渤中A-4油藏馆陶组,再通过垂向输导至浅层明下段,然后沿横向广覆砂体运移至渤中A-2油藏明下段,从而形成了现今的岩性油气藏。

By analyzing the characteristics of source rocks and comparing the biomarker parameters of crude oil samples from typical wells,the crude oil sources and its migration and accumulation patterns of lithologic reservoirs of the lower Minghuazhen Formation of Neogene in Bozhong A-2 area in the southwest belt of Bozhong Sag were studied.The results show that:(1)The source rocks of the third member of Dongying Formation(E_(3)d_(3))and the first and third members of Shahejie Formation(E_(2)s_(1),E_(2)s_(3))are developed longitudinally in the southwest belt of Bozhong Sag.The source rocks of E_(3)d_(3) have C_(19)TT predominance,a high Ts abundance value and a“V”-shaped distribution of C_(27)-C_(28)-C_(29) regular sterane.The source rocks of E_(2)s_(1) have C_(23)TT predominance,similar Ts and Tm abundance values,a high abundance value of gammacerane and a“L”-shped distribution of C_(27)-C_(28)-C_(29) regular sterane.The source rocks of E_(2)s_(3) have C_(21)TT or C_(23)TT predominance,high Ts abundance value,and a“V”-shaped distribution of C_(27)-C_(28)-C_(29) regular sterane,with C_(27) predominance.(2)The difference distribution of physical parameters and gas chromatogram of crude oil shows that the filling capacity of crude oil in the southeast well area of Bozhong A-2 reservoir is stronger than that in the middle well area.The C_(27)-C_(28)-C_(29) regular sterane distributed in a“L”shape and the peak value of 4-methylsteranes is large.In the upper part of the lower Minghuazhen Formation,the C19TT/C23TT is smaller,the MPI1 and MPI2 parameters are larger,total oil has a slightly heavy carbon isotope,indicating that the oil source is mainly supplied by E2s1 and supplemented by E_(2)s_(3).(3)1-methylphenanthrene,9-methylphenanthrene,C_(29)ααS/(S+R),C_(29)ββ/(αα+ββ),dibenzothiophene series and QGF index parameters change regularly in each well of Bozhong A-2 reservoir,indicating that the crude oil is mainly charged from east to south to northwest.The comparison results of crude oil biomarker show that the deep crude oil in the southwest belt of Bozhong Sag firstly accumulated in Guantao Formation in Bozhong A-4 reservoir,transported vertically to the shallow lower Minghuazhen Formation,and then migrated horizontally along the wide sand bodies to lower Minghuazhen Formation of Bozhong A-2 reservoir,thus forming the current lithologic reservoirs.