大民屯凹陷隐蔽型潜山成藏条件与勘探

大民屯凹陷隐蔽型潜山是低平或负向形态的元古宇或太古宇基底潜山,中生界、古近系房身泡组或沙四段的非渗透层对不整合面形成封闭,在多期构造运动改造、风化剥蚀作用下,具有多种较好的储集岩性和多期发育的裂缝型储集层,潜山内幕层状地层或层状岩性组合与微幅度断层一起构成潜山内幕圈闭,来自各生油洼陷的油气首先沿连通油源的深大断裂垂向运移,之后沿不整合面长距离侧向运移至隐蔽型潜山圈闭,形成潜山油藏。大民屯凹陷元古宇隐蔽型潜山勘探已见到良好效果,发现了安福屯、平安堡、东胜堡西等一系列隐蔽型潜山油藏。由于形态和成藏条件的隐蔽性,隐蔽型潜山很难被发现,但其特征决定其在各个凹陷广泛分布,勘探空间十分广阔,在进一步加强分布规律、成藏机制、勘探方法等方面研究的基础上,有望为老油区潜山勘探开拓新领域。图9参18

Subtle buried hill reservoir accumulation conditions and exploration in Damintun Sag, Liaohe Oilfield

Subtle buried hills(SBHs) of Damintun Sag refer to those low-or negative-shaped Protozoic or Archaean basement buried hills.The impervious Mesozoic Formation,Palaeogene Fangshenpao Formation or Es4 Formation seals the unconformity surface.Under multi-stage tectonic movement and weathering,the buried hills form favorable reservoir lithologies and fractured reservoirs.Inner buried hill laminar formation or lithology association together with minor faults form inner buried hill traps.Oil and gas from hydrocarbon kitchens migrate first along vertical deep fractures connecting source,laterally to SBH traps over a long distance along unconformity surfaces to form SBH reservoirs.The Protozoic SBH reservoirs have been discovered in the sag,including Anfutun,Ping'anpu and Dongshengpu.SBHs are deemed to be distributed extensively in depressions by their characteristics,and the space of exploration remains very vast.