准噶尔盆地陆梁油田白垩系油气运聚特征的新认识

New perspective on hydrocarbon migration and accumulation of Cretaceous oil reservoirs of Luliang oil field,Junggar basin

前人在研究陆梁油田白垩系油气运聚特征时,多侧重于断裂-不整合体系对油气的输导作用和侏罗系油气藏的次生调整作用,很少关注清水河组对油藏形成的贡献.本文以构造演化史、烃源岩生排烃史等地质背景为基础,通过单井垂向上连续颗粒定量荧光分析、地震层位精细标定、连井剖面砂体对比等技术方法,证实了石南47井区清水河组早期存在古油藏,重新认识了陆梁油田白垩系油藏形成的过程,并为白垩系油气勘探提供了新思路.研究结果表明:1)白垩纪,三个泉凸起西段清水河组发育低幅度背斜构造,受下乌尔禾组烃源岩生成的油气和侏罗系油藏次生调整油气的共同充注,形成规模古油藏,表现在石南47井区2 040~2 084m的QGF指数较大;2)古近纪末的喜马拉雅构造运动使得清水河组背斜幅度变小甚至消失,三个泉凸起白垩系及以上地层变成南低北高的形态,使得清水河组油气向上向北调整,由2 040~2 048 m的QGF-E强度较低可以证实,调整的油气运移至呼图壁河组圈闭中重新聚集成藏;3)现今陆梁油田白垩系油藏的形成不仅仅受断裂、不整合、侏罗系油气的控制,也与清水河组古油藏的形成与再分配密切相关.

Previous studies of hydrocarbon migration and accumulation of Cretaceous in the Luliang oil field mainly focus on the influences of fault-unconformity on hydrocarbon migration and the effects of Jurassic primary oil pools adjustment on hydrocarbon accumulation.However,little attention has been paid on the contribution of the Qingshuihe formation.Based on the geological background including tectonic evolution,hydrocarbon generation-expulsion history and through research methods including single-well continuous Quantitative Grain Fluorescence（QGF）analysis,meticulous horizon calibration,sand body correlation,paleo oil pools of Shinan 47 well block were proved,new understanding for the formation process of Cretaceous reservoirs in the Luliang oil field was proposed,and new ideas for Cretaceous oil exploration wereprovided.The results are mainly as follows.1）In the Cretaceous,the Qingshuihe formation developed low amplitude anticlines.Charged by oil from lower Wu＇erhe source rock and the Jurassic primary reservoirs,large-scale paleo oil pools were formed in those anticlines,manifested as the QGF index of 2 040—2 048 mgreater than 4.2）The Himalayan Movement during the Late Paleogene made the shape of low amplitude anticlines decrease or even disappear.The strata shape of the Sangequan uplift evolved into a monocline that was high in the north and low in the south,resulting in the oil adjustment.This was proved by the fact that QGF-E intensity of 2 040—2 048 m was rather low.The adjusted oil was re-accumulated into the Hutubihe formation and formed new oil pools.3）The current Cretaceous oil pools in the Luliang oil field is not only controlled by fault,unconformity,or Jurassic primary oil pools,but also deeply influenced by the formation and re-distribution of the Qingshuihe paleo oil pools.