塔中北斜坡奥陶系走滑断裂带与岩溶储集体发育模式

Model for Strike-Slip Fault Zones and Karst Reservoir Development of Ordovician in Northern Slope of Tazhong Uplift, Tarim Basin

塔里木盆地塔中北斜坡奥陶系发育多条北东—南西向走滑断裂带,沿这些走滑断裂带多口钻井在奥陶系碳酸盐岩中获得油气发现。研究碳酸盐岩内幕储集体特征、成因及其与走滑断裂带的关系,是塔中北斜坡奥陶系油气勘探面临的关键问题之一。通过对4口典型钻井奥陶系储集体发育特征、岩石学和地球化学资料的综合分析,结合区域地质背景及火成岩发育特征,提出储集体发育可能与不同性质的深成岩溶流体改造有关,其中A井可能与区域火成岩侵入体相关流体有关,而B井、C井和D井可能与深部含硅质地层热液流体有关。通过对4口井所在的3条走滑断裂带的分段性和变形强度进行半定量解剖,并与实钻情况对比,提出走滑断裂带分段性可能控制了储集体发育部位,张扭部位较压扭部位更为有利,而变形强度控制了储集体发育规模,变形强度大的断裂带储集体规模更大。建立了塔中北斜坡奥陶系走滑断裂带与深成岩溶储集体的发育模式,为奥陶系断裂带碳酸盐岩内幕储集体的油气勘探与评价提供了新的思路。

Several NE-SW strike-slip fault zones are distributed in the Ordovician strata in northern slope in Tazhong uplift of Tarim basin,along which a lot of oil and gas seepages were discovered in carbonate rocks of the Ordovician from many drilled wells. Study on the insidecarbonate reservoir feature and origin, as well as the relationship with the strike-slip fault zones is one of key issues for petroluem explora-tion in it. This paper presents comprehensive analysis of the development features, lithologic and geochemical data from 4 typical wells（i.e.A, B, C, and D wells） drilled in the Ordovician reservoir. And combined with the regional geologic setting and igneous rock characterisitcs,it considers that such a reservoir development may be related to plutonic karst fluid transformation with different properties, among whichWell A may be related with the regional igneous intrusions-relevant fluid, while Wells B, C, D could be related to the deep hydrothermalfluids in silicon formations. Based on these, the segmentation and deformation intensity of 3 strike-slip fault zones are analyzed semi-quanti-tatively. Compared with the actual drilling situations, it is concluded that the segmentation of strike-slip fault zones may control the positionof the reservoirs, where transtension part is better than pressure torsion part; whereas transformation intensity may control the scale of it,and the greater the intensity, the bigger the scale is. Finally, this paper develops the model for such fault zones and plutonic karst reservoirsin this area, so as to provide a new idea for petroleum exploration and evaluation of this inside carbonate reservoir.