东营凹陷永安镇油田沙四段永1砂砾岩体演化过程及成藏意义

Evolution process and hydrocarbon accumulation significance of Yong1 glutenite body in Es4 Member in Yonganzhen Oilfield,Dongying Sag

东营凹陷永安镇油田永1砂砾岩体演化过程的不明确使油藏类型难以确定,制约了下步勘探部署工作的开展。通过三维地震解释、测井和录井分析、岩心观察、薄片观察及物性分析等方法,对永1砂砾岩体的演化过程及其对油气成藏的影响进行研究。结果表明:永1砂砾岩体沉积符合“沟扇对应”原理,由西北部陈家庄凸起提供物源,碎屑沿凸起与永1地区之间的北西南东向古沟道搬运;永1砂砾岩体孤立凸起的形态由辉绿岩的后期侵入作用导致,侵入时间最早发生在沙四段上亚段纯上次亚段沉积时期,此时辉绿岩体仅侵入花岗片麻岩基底,未发生岩体刺穿,此过程可持续到沙三段沉积早期;沙三段沉积中期之后,辉绿岩体持续侵入,永1砂砾岩体持续隆起,逐渐发生岩体刺穿,此过程可持续至沙三段沉积晚期;岩浆活动导致砂砾岩周缘产生高角度断层及裂缝,改善储层储集空间及渗流条件的同时,有效地沟通了沙四段和沙三段的烃源岩,形成了油气有利聚集区。

The unclear evolution process of Yong1 glutenite body in Yonganzhen Oilfield,Dongying Sag adds difficulties to determine the reservoir type,which restricts the development of further exploration. The evolution process of Yong1 glutenite body and its influence on hydrocarbon accumulation are studied through 3D seismic interpretation,well logging and mud logging analysis,core observation,thin section observation,and physical property analysis. The results show that Yong1 glutenite body deposition conforms to the principle of“channel-fan correspondence”,and its provenance is provided by Chenjiazhuang uplift in the northwest,the debris transported along the NW-SE paleochannel between the uplift and Yong1 area. The isolated uplift of the Yong1 sand-conglomerate body are caused by the late intrusion of diabase. The earliest intrusion occurred in the period of the Upper Submember of the 4th Member of Shahejie Formation(the Upper Es4 Member)while diabase only intruded into the granitic gneiss basement and did not punctured the rock mass,and this process lasted until the early sedimentation of the 3rd Member of Shahejie Formation(the Es3 Member). After the middle sedimentary period of the Es3 Member,diabase continued to intrude,Yong1 glutenite body continued to uplift,and rock was punctured gradually. This process lasted until the late sedimentary period of the Es3 Member. Magmatic activity leads to the formation of high-angle faults and fractures in the periphery of the glutenite body,which improves the reservoir space and percolation conditions,and effectively communicates the hydrocarbon source rocks in the Es3 and Es4 Member,forming a favorable accumulation area for hydrocarbon.