渤海湾盆地歧口凹陷古近系沉积体系重建与储集层评价

应用陆相层序地层分析与传统沉积学等方法,探讨渤海湾盆地歧口凹陷古近系沉积体系的空间展布规律与有利储集层发育特征,为高勘探程度区油气二次勘探部署提供支撑.研究结果表明歧口凹陷古近系斜坡作为古地貌单元的主体,为大面积岩性油气藏的形成奠定了地质基础;除四大盆外隆起物源外,孔店、港西等盆内凸起也是碎屑沉积体系的重要物质来源,斜坡区既富泥也富砂;古近系相序完整,环湖规模性发育了辫状河三角洲、扇三角洲、远岸水下扇、湖泊碳酸盐岩等相类型;中深层储层具有原生、次生孔隙与微裂缝共存的特点,在异常高压、早期油气充注和次生溶解等作用下,中深层也发育优质储层,斜坡区的勘探下限可达5km;多类储集体与歧北挠曲斜坡、板桥斜坡、埕北断坡等匹配形成地层超覆、不整合遮挡、上倾尖灭等地层-岩性圈闭带.勘探结果发现了歧北斜坡、埕北断坡亿吨级储量区,板桥斜坡形成了千万吨级效益储量区.斜坡区作为断陷湖盆负向构造单元,是地层-岩性油气藏有利的勘探领域.

Reconstruction of Paleogene sedimentary system and reservoir evaluation in Qikou Sag,Bohai Bay Basin,China

The spatial distribution pattern of sedimentary system and development characteristics of favorable reservoir of Paleogene in Qikou Sag of Bohai Bay Basin are discussed on the basis of continental sequence stratigraphy analysis and traditional sedimentology,so as to provide support for the second exploration and deployment of hydrocarbon in highly prospected area.It shows that the Paleogene slopes in Qikou Sag lay the foundation for the formation of lithological hydrocarbon reservoirs.In addition to the four provenances of uplift outside the basin,the bulges,such as Kongdian,Gangxi,in the basin are also important provenances of clastic sedimentary system.The slope area is rich in mud and sand;it has complete sedimentary-facies succession of Paleogene system,including well developed braided river delta,fan delta,offshore fan and lacustrine carbonate rocks in the lake,characteristic of coexistence of primary pores,secondary pores and micro-fractures in the medium-deep reservoir.The early oil and gas charging,secondary dissolution and the effect of the abnormal high pressure play an important role in the formation of high quality reservoirs.It reveals that the lower limit of exploration can reach down 5 km in the slope area.Many types of reservoirs match with Qibei bend slope,Banqiao slope and Chengbei fault slope and form the stratigraphic and lithologic traps,such as stratigraphic overlap traps,unconformity screened traps,upward tilting traps and so on.Exploration indicates that the Qibei slope,Chengbei fault slope have 100 million tons scale reserve and 10 million tons scale reserve area in Banqiao slope.As a faulted lacustrine basin,the slope is a favorable exploration area of stratigraphic and lithologic reservoirs.