一种板内小尺度走滑断层平面分段研究方法——以塔里木盆地顺北5号断层中北段为例

近年来在顺北地区1号和5号走滑断层带上获得了重大的油气突破，证明了在塔里木盆地内发育的小尺度走滑断层对断控油气藏具有控藏、控储的特征。该类走滑断层在剖面上贯穿多套古生代地层，纵向结构复杂，在空间上为深层线性走滑叠加浅层雁列正断层的构造样式，钻井揭示在断层带上不同分段的井产能差异明显，表明走滑断层在奥陶系碳酸盐岩顶界面的分段性对油气成藏具有重要的控制作用。本文选取顺北5号断层中北段作为研究对象，针对深层不同层系线性走滑断层分段特征差异明显这一特征，基于不同尺度下断层的断距与分段长度之间的相关性及多断层演化理论，提出了利用沿着走向等间距统计断层的垂向断距变化的方法对深层线性走滑断层开展分段性研究工作，该方法综合了断层的活动强度、演化程度和剖面构造形态来分析断层的分段特征，适用于不同性质的断层分段性特征研究。研究表明5号断层中北段在奥陶系碳酸盐岩顶界面可划分为14段，在寒武系膏盐岩层顶界面可划分为10段，两个层系的断层分段性在空间上具有继承性与差异演化的特点，其中寒武系膏盐岩滑脱构造中的膏盐逃逸对油气的疏导具有破坏作用，奥陶系碳酸盐岩顶断层活动强度、分段叠接样式、断层分段不同位置对断控缝洞型储层发育规模具有重要的控制作用，揭示了断层在平面上的分段特征及纵向结构对断控缝洞型油气成藏具有重要的控制作用。

A Method for Plane Segmentation of Small-Scale Intraplate Strike-Slip Faults:A Case of the Middle-North Segment of Shunbei No.5 Fault in Tarim Basin

In recent years, major oil and gas breakthroughs have been made around the No. 1 and No. 5 strike-slip fault zones in Shunbei area, which reveals that the small-scale strike-slip faults developed in Tarim basin have the characteristics of controlling reservoir and reservoir of fault-controlled oil and gas reservoirs. The strike-slip faults cut through several sets of Paleozoic strata in the section, which complicates the longitudinal structures that show a style of deep linear strike-slip superimposed shallow echelon normal fault in space. Drilling reveals that the productivity of wells is significantly different in different sections of the fault zone, and the segmentations of the strike-slip faults at the top interface of Ordovician carbonate rocks plays an important role in controlling oil and gas accumulation. The middle-north section of Shunbei No. 5 fault is selected as the research object based on the correlation between the fault distances and segment lengths at different scales and the theory of multi-fault evolution. A method is proposed to carry out segmental research on the deep linear strike-slip faults by using the changes of statistical vertical distances along the strike faults. This method is universal, and it can be used to study the segmentation of different types of faults, combining with the intensity of fault activity, the degree of evolution, and the structural shape of the section, so as to analyze the segmentation characteristics of the faults. The study shows that the middle-north part of No. 5 fault can be divided into 14 segments at the top interface of Ordovician carbonate rocks and 10 segments at the top interface of Cambrian gypsum-salt strata. The fault segmentations of the two strata have the characteristics of inheritance and differential evolution in space. The result shows that the escape of gypsum salt from the detachment structure of the Cambrian gypsum salt rock has a destructive effect on the drainage of oil and gas; While the intensity of the fault activity, segmented overlap pattern, and different positions of fault segments on the top of Ordovician carbonate rocks play an important role in controlling the development scale of fault-controlled fracture-cave reservoirs. This implies that the segmented characteristics and vertical structure of in-plane faults play an important role in controlling fracture-cave hydrocarbon accumulation.