渤海湾盆地新太古代结晶岩潜山裂缝发育的露头模型

Fracture-Occurring Outcrop Model in Neoarchean Crystalline Rock-Buried Hill,Bohai Bay Basin,North China

新太古代结晶岩基底潜山是渤海湾盆地重要的油气勘探领域,裂缝的发育与分布是该类潜山油气成藏研究的重点与难点,通常潜山裂缝储层发育于断裂带。通过对秦皇岛地区鸽子窝与北戴河新太古代结晶岩露头断裂带与区域性构造节理带裂缝观测与描述,建立了裂缝发育的露头模型。研究表明,断裂带由核部碎裂带与两侧节理密集带组成,单侧节理密集带的宽度大于40m,整个断层带的宽度大于100m。节理密集带的线密度可达到28条/m,而且裂缝尺度长,多个方向的裂缝构成连通的网络系统,是该类裂缝储层发育的最有利部位。节理密集带以外的区域性节理发育带,因裂缝发育密度低、尺度小、彼此不连通,不能形成有效裂缝储层。潜山裂缝储层的分布受断层的控制呈现高度的非均质性,裂缝发育带与致密带在空间上构成不规则块状分布。

The Neoarchean crystalline rock-buried hill is an important area for petroleum exploration in the Bohai Bay Basin. The development and distribution of fracture in the buried-hill reservoirs is the key to the study on this type of oil accumulation, and the fractured buried-hill often occurs within faulted Zone. By the observation and description on the fracture in the Neoarchean crystalline rock outcrops,a fracture-occurring model has been created. It is clear that the Geziwo fault zone is composed of fault core and its two side- damage zones,in which fractures or joints occur densely,with a maximum fracture density of 28 fractures per meter. Each damage zone has a width exceeding 40 meters,and the whole width of the fault zone is more than 100 meters. In the damage zones,the main fractures parallel to the fault strike densely occur and extend long,and the several sets of fractures with different strikes constitute a network where the fractures are connected with each other. Therefore, the damage zone could act as effective reservoir. In contrast, the fractures in regional joint-developing zone occur with low density,minor size and unconnected, consequent- ly,the regional joint-developing zone could not become effective reservoir. The fractured reservoir in crys- talline rock-buried hill is featured with heavy heterogeneity,and the fractured and the un-fractured crystal- line rocks alternately occurred irregularly in the three dimensions.