辽中凹陷西斜坡古近系东三段湖底扇发育模式及大油田发现  

Sedimentary model of sublacustrine fan of the third member of Paleogene Dongying Formation and large-scale oilfield discovered in western slope of Liaozhong Sag

作　　者：牛成民 惠冠洲 杜晓峰 官大勇 王冰洁 王启明 张宏国 NIU Chengmin;HUI Guanzhou;DU Xiaofeng;GUAN Dayong;WANG Bingjie;WANG Qiming;ZHANG Hongguo(Tianjin Branch of CNOOC Limited,Tianjin 300459,China)

机构地区：[1]中海石油(中国)有限公司天津分公司,天津300459

出　　处：《岩性油气藏》2024年第2期33-42,共10页Lithologic Reservoirs

基　　金：中海石油(中国)有限公司“七年行动计划”科技重大专项课题“渤海油田上产4000万吨新领域勘探关键技术”(编号:CNOOCKJ 135 ZDXM 36 TJ 08 TJ)资助。

摘　　要：通过地层层序研究、古地貌恢复、锆石测年和地震资料分析等,从物源体系、古地貌、坡折体系和湖平面变化等方面探讨了辽中凹陷西斜坡古近系东营组三段(东三段)湖底扇的发育模式,并对油气藏的特征及成藏模式进行了研究。研究结果表明:(1)辽中凹陷西斜坡东三段湖底扇砂体表现为“物源-坡折带-湖平面”控制的富砂模式;物源主要来自燕山褶皱带,其次为辽西凸起,大规模的物源供给和变质岩的母岩区为湖底扇的形成提供了碎屑物质和优质的储集砂体;沉积坡折带控制湖底扇重力流卸载位置,断裂坡折带形成的微古地貌变化控制局部砂体搬运方向和差异富集程度;湖平面变化与物源体系变化耦合形成的三角洲、湖泊和湖底扇沉积在空间上反复叠置发育,为岩性圈闭的形成提供了良好的保存条件。(2)旅大10-6油田湖底扇岩性主要为中—细粒长石岩屑砂岩,颗粒粒度较小,以重力流沉积为主;孔隙类型主要为原生粒间孔和溶蚀粒间孔,见少量粒内溶孔,孔隙发育一般,连通性较差;湖底扇发育具有垂向上多期叠置、平面上连片的特征,位于斜坡中部的中扇亚相具有明显的滑塌变形构造,是最有利的勘探相带。(3)旅大10-6油田湖底扇油藏是辽中凹陷西斜坡从构造圈闭勘探转为岩性圈闭勘探的重大发现,实现了渤海油田斜坡带古近系湖底扇型岩性油气藏勘探领域的重大突破,共发育11个油藏和9个气藏,油气藏相互独立、储量规模大、丰度高,探明油当量为3000×10^(4)t,原油物性好、探井测试产能高,为“汇聚脊-通源断层-顺向砂体”三元耦合成藏模式。Through stratigraphic sequence research,paleogeomorphological restoration,zircon dating and seismic data analysis,the sublacustrine fan development model of the third member of Paleogene Dongying Formation(Ed3)in western slope of Liaozhong Sag was discussed from the aspects of source system,paleogeomorphology and slope break system and lake level change,and the reservoir characteristics and accumulation model were studied.The results show that:(1)The sand bodies of the sublacustrine fan in the western slope of Liaozhong Sag are characterized by a sand-rich model controlled by“source-slope break zone-lake level”.The sources are mainly from Yanshan fold belt,followed by Liaoxi uplift.Large-scale source supply and parent rock area of meta-morphic rocks provide clastic materials and high-quality reservoir sand bodies for the formation of the sublacus-trine fan.Sedimentary slope break zones control the unloading position of gravity flow in the sublacustrine fan,and the micro paleogeomorphic changes formed by the fault slope break zones control the direction of local sand body transport and the degree of differential enrichment.The coupling of lake level changes and source system changes has resulted in the repeated stacking and development of delta,lake,and sublacustrine fan sediments in space,providing good preservation conditions for the formation of lithologic traps.(2)The lithologies of the sub-lacustrine fan in Lvda 10-6 oilfield are mainly medium to fine grained feldspar lithic sandstone,with smaller par-ticle size and mainly composed of gravity flow sedimentation.The pore types are mainly primary intergranular pores and dissolved intergranular pores,with a small amount of intragranular dissolved pores.The pore develop-ment is average and the connectivity is poor.The development of the sublacustrine fan has the characteristics of vertical multi-stage overlap and planar continuity.The middle fan subfacies of the sublacustrine fan located in the middle of the slope have obvious collapse deformation structures,

关 键 词：湖底扇 古地貌 坡折体系 沉积模式 油气成藏模式 斜坡带 东营组三段 古近系 辽中凹陷 

分 类 号：TE122.1[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]