涠西南二号断裂带构造特征及其对成藏的影响

Structural characteristics of the No.2 fault zone in Weixinan Sag and its influence on reservoir formation

涠西南二号走滑断裂带及其周缘岩性圈闭是近年来勘探的热点,开展走滑断裂带形成演化及其对油气成藏的控制作用研究对下步勘探具有重要指导意义。利用最新的地震、钻井资料,对二号断裂带进行了系统综合研究。研究表明二号走滑断裂带西段、中段、东段活动具有明显的差异性,其中中段走滑活动最为强烈,走滑特征明显,西段和东段相对较弱。二号走滑断裂带差异活动控制着流沙港组一段(流一段)上层序、涠洲组三段(涠三段)古地貌的形成,从而影响沉积体系展布,进而控制岩性圈闭的发育。流一段上层序沉积时期,二号断裂带中段走向斜坡及其对应的沟槽位置是岩性圈闭发育的有利区,涠三段沉积时期,辫状河三角洲主河道与二号雁列断裂耦合区是构造+岩性圈闭发育的有利区。走滑断裂带主干断层和派生的次级调节断层是油气运移输导的重要通道,对油气成藏具有重要意义。走滑断裂对流一段上层序、涠三段油气的分布具有明显的控制作用。

In recent years,the No.2 strike-slip fault zone and its surrounding lithological trap in the Wexinan Sag are hot spots for exploration.The study on the formation and evolution of the strike-slip fault zone and its controlling effect on hydrocarbon accumulation is significance for the next exploration.This paper conducted a systematic study of the No.2 fault zone by utilizing the latest seismic and drilling data.The research shows apparent differences in the activities of the western,middle and eastern sections of the No.2 strike-slip fault zone.The middle section has the strongest strike-slip activity and obvious strike-slip characteristics,while the western and eastern sections are relatively weak.The differential activity of the No.2 strike-slip fault zone controls the paleogeomorphology of the upper sequence of the first Member of the Liushagang Formation and the third Member of the Weizhou Formation,thereby affecting the distribution of the sedimentary system,and then controlling the development of lithological traps.During the depositional period of the upper sequence in the first Member of the Liushagang Formation,the strike slope in the middle section of the No.2 fault zone and its corresponding groove position are favorable areas for developing lithological traps.During the depositional period of the third Member of the Weizhou Formation,the coupling area between the main line of the braided river delta and the No.2 echelon fault is a favorable area for developing structural and lithologic traps.The main fault and the derived secondary regulation fault in the strike-slip fault zone are essential channels for oil and gas migration and drainage,which are significance to oil and gas accumulation.The strike-slip fault has a pronounced control effect on the distribution of oil and gas in the upper sequence of the first Member of the Liushagang Formation and the third Member of the Weizhou Formation.