塔里木盆地中部走滑断裂系统分布格局及其成因

Distribution pattern and formation mechanism of the strike-slip fault system in the central Tarim Basin

塔里木盆地中部(以下简称台盆区)奥陶系碳酸盐岩走滑断裂发育,控储控藏作用明显,但对于走滑断裂的成因机制尚不明晰,制约了该区油气勘探开发的进程。为此,基于三维地震解释成果,结合前人的研究成果及认识,描述了台盆区走滑断裂的总体展布格局,分析了走滑断裂的几何学特征和形成时期,并结合先存构造背景和区域构造应力场探讨了走滑断裂的形成机制,预测了潜在走滑断裂的分布规律。研究结果表明:①台盆区走滑断裂受控于先存构造,在其西南、东南和北部3面挤压应力作用下形成统一的大型走滑断裂系统,形成期为中奥陶世末期;②台盆区走滑断裂整体格局中的FⅠ5断裂最为重要,调节了东、西两侧地块的运动差异,是台盆区东、西部走滑断裂系统的分界线,而FⅠ10、FⅠ17等转换断裂则分解了南北向地层缩减,形成了断裂体系的边界,控制了断裂体系中走滑断裂的发育范围;③台盆区走滑断裂系统整体可以被划分为塔北隆起纯剪断裂体系、塔中凸起左行断裂体系、巴楚凸起右行断裂体系和阿满过渡带转换断裂体系共4个体系。结论认为:①FⅠ5、FⅠ10、FⅠ17等断裂活动强度大,对储层改造及油气疏导作用强,是目前断控区最有利的油气勘探目标;②预测FⅠ5断裂西侧的阿满过渡带可能发育与FⅠ10断裂对称的转换断层,巴楚凸起、塔中凸起西部可能发育北东向走滑断裂,是下一步油气勘探值得关注的对象。

Strike-slip faults are developed in the Ordovician carbonate rocks of central Tarim Basin(hereinafter referred to as"platform basin area")and they have an obvious control effect on reservoirs and hydrocarbon accumulation.However,the formation mechanism of strike-slip faults is not figured out clearly,which hampers the oil and gas exploration and development progress in this area.Based on 3D seismic interpretation results,combined with previous research achievements and understandings,this paper describes the overall distribution pattern of strike-slip faults in the platform basin area,and analyzes their geometric characteristics and formation periods.Then,based on the pre-existing tectonic background and regional tectonic stress field,the formation mechanisms of strike-slip faults were discussed and the distribution laws of potential strike-slip faults were predicted.And the following research results were obtained.First,the strike-slip faults in the platform basin area are controlled by pre-existing structures and a united large strike-slip fault system was formed under the action of compression stress from southwest,southeast and north at the end of Middle Ordovician.Second,FⅠ5 fault in the overall pattern of strike-slip faults in the platform basin area is the most important,which adjusts the movement difference between the east and the west blocks,which is the boundary between the east and the west strike-slip fault systems in the platform basin area.The transition faults such as FⅠ10 and FⅠ17 faults decompose the reduction of north-south strata,which form the boundary of the fault system and control the development range of strike-slip faults in the fault system.Third,the strike-slip fault system in the platform basin area can be divided into four systems,namely pure shear fault system in Tabei uplift,left-lateral fault system in Tazhong uplift,right-lateral fault system in Bachu uplift,and transform fault system in Aman transition zone.In conclusion,fault FⅠ5,FⅠ10 and FⅠ17 are of high fault activity strength and they have a strong effect on reservoir reworking and oil and gas migration,so it is currently the most favorable oil and gas exploration target in fault controlled areas.What's more,it is predicted that a transform fault symmetrical to fault FⅠ10 may be developed in the Aman transition zone to the west of fault FⅠ5 and a NE trending strike-slip fault may be developed in the west of Tazhong uplift and Bachu uplift,which is a worthy object for the next oil and gas exploration.