塔里木盆地玉北地区中-下奥陶统储集体断裂与裂缝特征

通过薄片、岩心观察结合成像测井以及三维地震等资料对玉北地区鹰山组海相碳酸盐岩储层进行了研究,认为此区域虽然剥蚀严重,大范围缺失上奥陶统,但并非典型的风化壳型储层,具有明显的断控型岩溶储层特征.储集空间主要为小型溶蚀孔洞-裂缝,且区域上明显受到断裂系统控制.文章从宏观角度分析了玉北地区断裂发育的期次和构造样式以及有效缝的走向,之后转入微观裂缝特征的研究,最后探讨裂缝与储层改造的关系.研究认为地表水沿断裂下渗溶蚀是储层改善的关键,埋藏环境下的成岩作用(深部热液溶蚀、有机酸作用)对储层存在影响,但并非储集空间形成的主要因素.玉北地区奥陶系全井段裂缝型储层都发育,尤其在顶部风化壳和底部云灰岩性过渡段裂缝发育,其东部断褶区中构造层发育的北东向盖层滑脱型逆冲推覆断裂系统,与下构造层中发育的北东向直立走滑断裂带位置相近,在东部断垒带共同构成了油气运移通道,使之成为玉北地区裂缝-孔洞型储层发育的优势地区.

Fault and fracture characteristics of the Middle-Lower Ordovician in Yubei area,Tarim Basin

The Yingshan Formation marine carbonate reservoirs in Yubei Area were examined by applying various data such as cores, FMI, 3D seismic attributes and thin sections. Although extensive erosion has led to the absence of the Upper Ordovician in the study area, the carbonate reservoirs are not typical weathering-crust reservoirs, but fault-controlled karst reservoirs. The reservoir spaces are mainly small-scale solution vugs and fractures, the distribution of which is strongly controlled by fault systems. This paper first studied the timing of fault, structural styles and the azimuth of fractures in a macroscopic view, then analyzed the features of fracture in a microscopic view, and finally discussed the relationship between the fractures and reservoir reconstruction. The results show that meteoric corrosion downward along faults is critical to reservoir reconstruction. Whereas the burial diagenesis (deep hydrothermal erosion or organic acid) also has influences on reservoir pores but is not the main factor. Faulted reservoirs occur in the whole Ordovician in Yubei Area, especially in the top weathering crust and the bottom transition from dolomite to limestone. The overthrust system of NE-trending cap rock detachment type in the middle structural layer of east fault-fold structural belt is adjacent to the NE-trending vertical strike slip fault in the lower structural layer. They together consist of the hydrocarbon migration pathway in the eastern faulted horst belt, which is the most favorable zone for fractured or fractured-vuggy reservoirs.