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根据露头、岩心、薄片、古地磁、成像测井、岩石力学实验等资料,对东濮凹陷北部三叠系砂岩储层构造裂缝特征及形成期次进行分析。东濮凹陷三叠系砂岩储层主要发育北北东、北东和近东西向3组高角度构造裂缝,裂缝走向近于平行或垂直主断层,倾向为北西和南东。二马营组裂缝较为发育,和尚沟组和刘家沟组裂缝相对不发育。储层裂缝为3期,分别为燕山早期的北西向扩张裂缝和北北西、北西西向剪切裂缝,燕山晚期形成北东向拉张裂缝,喜马拉雅期形成北北东、北东向拉张裂缝、北北东向剪切裂缝和东西向扩张裂缝。古、今构造应力场和岩石力学性质的各向异性分析表明,现今构造应力场最大水平主应力和岩石抗压强度的各向异性均影响燕山早期北西向裂缝的张开度及有效性。储层裂缝表现为两期,分别为燕山晚期的北东向拉张裂缝、喜马拉雅期的北北东、北东向拉张裂缝,北北东向剪切裂缝和东西向扩张裂缝。研究结果阐明了东濮凹陷北部三叠系砂岩储层构造裂缝特征及发育规律。
According to the data of outcrop, core, thin slice, paleomagnetic, imaging logging and rock mechanics experiments, the tectonic fractures of Triassic sandstone reservoirs and their formation period in northern Dongpu Depression are analyzed. The Triassic sandstone reservoirs in Dongpu sag mainly develop three high-angle structural fractures in North, East, North East and Near East-West faults. The fractures are nearly parallel or perpendicular to the main faults, with a tendency of North and South East. The cracks in Ermaying Formation are more developed, and the fractures in HeShang Formation and Liujiagou Formation are relatively undeveloped. There are 3 fractures in the reservoir, which are northwest expansion fracture, north-northwest fracture and northwest-west fracture in the early stage of Yanshanian, north-east tensile fracture in the late Yanshanian period, northern-northeast and north-east tensile fracture in the Himalayan, North-east shear fracture and east-west expansion fracture. Anisotropy analysis of tectonic stress field and rock mechanical properties shows that the maximum horizontal principal stress of tectonic stress field and anisotropy of compressive strength of rock all affect the opening degree and validity of northwestern crack in early Yanshanian. The reservoir fractures are characterized by two phases, namely the northeastern extensional crack in the late Yanshanian period, the north-eastern easterly, the north-eastern extensional crack, the north-northeast shear fracture and the east-west expansion fracture in the Himalayas. The results of this study illustrate the tectonic fractures and development of Triassic sandstone reservoirs in the northern part of Dongpu Depression.