克拉苏构造带盐下超深层储层的构造改造作用与油气勘探新发现

塔里木盆地克拉苏构造带油气群下白垩统巴什基奇克组埋深超过6 000 m,储层基质渗透率低,裂缝普遍发育,构造对储层的改造作用明显,但博孜9井的勘探突破反映出不同区带间构造改造作用差异较大、非均质性极强,重新认识构造对储层的改造作用对于预测超深层储层、指导油气勘探生产具有重要的意义。为此,基于钻井取心、构造平衡恢复、裂缝充填物同位素测年、区块应力数值模拟等资料,结合流体包裹体、声发射古应力、铸体薄片等实验分析方法,从定性分析到定量计算、研究了克拉苏构造带油气群超深层储层的构造改造作用及其差异性。研究结果表明:①北部天山造山带及南部古隆起控制了该构造带储层的沉积格局及差异构造变形,形成巴什基奇克组储层"西薄东厚"的分布特征;②博孜区段古应力最小,构造变形主要为正向挤压、逆冲传播,局部井区为斜向压扭;③大北区段主要为斜向压扭,古应力较小,构造变形为逆冲叠置;克深区段古应力最大,构造变形主要为正向挤压、后缘逆冲抬升、前缘滑脱收缩;④差异构造变形使同一构造带不同构造变形样式的构造减孔量呈现出较大的差别,且控制了不同区段造缝期与成岩胶结的叠加影响、中晚期裂缝网络与油气成藏期的配置关系,加剧了储层的...

Structural reworking effects and new exploration discoveries of subsalt ultra-deep reservoirs in the Kelasu tectonic zone

The Bashijiqike Formation of Lower Cretaceous in the oil and gas group in the Kelasu tectonic zone of the Tarim Basin is deeper than 6 000 m with the characteristics of low reservoir matrix permeability, developed fractures and significant reworking effect of structure on reservoir. However, the exploration breakthrough of Well Bozi 9 reflects that the structural reworking effects in different zones vary greatly and the heterogeneity is quite strong. Therefore, recognizing the structural reworking effects on reservoirs again is of great significance in predicting ultra-deep reservoirs and guiding oil & gas exploration and production. In this paper, the structural reworking effects on the ultra-deep reservoirs in the oil and gas group of Kelasu tectonic zone and their diversity were qualitatively analyzed and quantitatively calculated using drilling coring, structural equilibrium and restoration, isotopic dating of fracture fillings and numerical simulation of block stress, combined with fluid inclusion analysis, acoustic emission paleo-stress analysis, casting slice and other experimental analysis methods. And the following research results were obtained. First, the Tianshan orogenic belt in the north and the paleo-uplift in the south dominate the sedimentary pattern and the differential tectonic deformation of reservoirs in this tectonic zone. As a result, the distribution characteristics of being "thin in the west and thick in the east" of the Bashijiqike Formation reservoir are formed. Second, in the Bozi Block, paleo-stress is the smallest, structural deformation is mainly in the form of forward compression and thrust propagation, and oblique compression and torsion occurs in local well blocks. Third, in the Dabei Block, oblique compression and torsion is dominant, paleo-stress is smaller and structural deformation is in the form of thrust stacking. And in the Keshen Block, paleo-stress is the highest and structural deformation is mainly in the form of forward compression, thrust and uplift of trailing edge, and slippage and shrinkage of leading edge. Fourth, differential tectonic deformation results in a large difference in the amount of structural reduction in the same structural belt with different structural deformation patterns. And it also controls the superimposed effects of fracture formation and diagenetic cementation in different blocks and the configuration relationship between fracture networks and oil & gas accumulation periods in the middle and late stages, and increases the reservoir heterogeneity. Therefore, the differential structural deformation is the basic reworking factor for the variation of productivity in different blocks. Fifth, the magnitude and direction of the current tectonic stress affect the fracture effectiveness. In the southern part, the compressive stress is strong, the intersection angle between the fracture direction of the higher position of the anticline and the current stress is smaller, and the fracture effectiveness is the best. Sixth, the type of structural fracture fillings is dependent on the structural diagenetic environment. In the northern block, the diagenetic environment of freshwater and semi-alkaline medium is dominant, so the type of fracture fillings is calcite, which is conducive to the acid fracturing of reservoir.