渤海湾盆地A稠油油田M层油水界面主控因素

Controlling Factors of Oil-Water Contact in M Layer of Heavy-Oil Field A,Bohai Bay Basin

A油田位于渤海湾盆地渤中坳陷北部石臼坨凸起西南端,是构造平缓、具有复式鼻状特征的砂岩稠油油藏。多井资料揭示,M层油水界面由东南向西北倾斜上升,高差达5.0~22.0 m;注示踪剂及动态生产资料证实,油水界面差异的井间,储集层具有连通性。据毛细管压力与浮力平衡理论分析认为,连通砂体内部油水界面差异主要受地层原油黏度及储集层物性的控制,地层原油黏度越大,储集层物性越差,则油水界面越高。不同程度的微生物降解,使地层原油黏度由东南向西北逐渐增大;废弃河道沉积和侧积层的发育,使储集层物性由东南向西北逐渐变差,2个因素共同导致了油水界面由东南向西北倾斜上升。

The oilfield A located at the southwestern end of Shijiutuo swell in the northern Bozhong depression of Bohai Bay basin,belongs to heavy?oil sandstone reservoirs featured with gentle and complicated nose?like structures.Drilling data shows that the oil?water contact(OWC)of M layer exhibits a SE?NW rising trend with the altitude difference of5.0~22.0m.Tracer data and production performance prove that the reservoir is continuous between wells with different OWCs.Analyses of capillary pressure and buoyance balance theory show that the differences of OWC in the connected sandbodies are mainly constrained by formation oil viscosity and reservoir physical properties;the larger the formation oil viscosity is,the poorer the reservoir physical properties are and the higher the OWC will be.Biodegradation of different levels results in the gradual rise of formation oil viscosity from southeast to northwest;the development of abandoned channel deposits and lateral accretion layers leads to worse and worse reservoir physical properties from southeast to northwest.Both the biodegradation and development of abandoned channel deposits and lateral accretion layers result in the SE?NW rising trend of the OWC.