塔里木盆地玛扎塔格构造带深层构造分析

Deep Structural Analysis of Mazatag Tectonic Belt in Tarim Basin

玛扎塔格构造带位于塔里木盆地麦盖提斜坡和巴楚隆起交界处,是和田河气田的主要储集构造带,石油地质条件优越。尽管前人对该地区做了大量研究,但由于其复杂构造变形严重影响了下部构造的地震成像,无法在地震剖面上直接识别出深部构造形态,其断裂带形成机制及深部展布形态仍存在争议。而深部构造的认识与油气勘探效益密切相关。本文基于面积-深度法对玛扎塔格构造带典型地震剖面进行量化分析,通过剖面浅层结构预测其深层构造特征。研究结果表明:①玛扎塔格中构造层构造变形主要受到深层基底断裂控制,而不是以中寒武统膏盐层为滑脱层的薄皮滑脱构造变形。结合区域地质背景和演化历史,深层基底断裂可能是前寒武纪拉张环境形成正断层的再活化。②玛扎塔格深部断裂的发育对该区域油气分布有重要的影响。玛扎塔格构造带油气资源丰富,目前主力油气层位于盐上碳酸盐储层,而中下寒武统是塔西南区域重要的烃源岩,中寒武统膏盐层作为一种有效的盖层,在区内连续分布。切穿膏盐层的深层基底断裂有利于沟通盐下烃源岩和盐上储层,有利于该区域的浅部成藏。

The Mazatag structural belt is located at the junction of the Meghetti slope and the Bachu Uplift in the Tarim Basin.It is the main reservoir structural belt of the Hetianhe gas field which is rich in oil and gas resources.Although a great deal of research has been done in this area,however,it is still difficult to identify the subsalt structure on the seismic profile directly due to its complex structure and poor seismic imaging.The models of formation mechanism and subsalt structure of the fault zone are still controversial.The accurate location of the deep structure is critical for oil and gas exploration.In this paper,the typical seismic profiles of the Mazatag tectonic belt are quantitatively analyzed by using area-depth method,on purpose of predicting the deep structural characteristics via shallow clear structure of the section.The results show that:(1)the deformation of the Mazatag is mainly controlled by deep and large fault,rather than the deformation of the thin skinned slip along the Middle Cambrian gypsum layer.Considering the regional geological background and evolution,the main fault might have re-activated the normal fault developed in Precambrian.(2)The development of the deep fracture of the Mazatag has a great impact on the hydrocarbon accumulation in the region.Nowadays,the main carbonate reservoir occurs above the Middle Cambrian gypsum layer,and the Middle and Lower Cambrian sequences are important source rocks in the southwestern Tarim Basin.As an effective caprock,the Middle Cambrian gypsum salt layer is continuously distributed in this area.The deep and large faults cut-through the Middle Cambrian gypsum layer are beneficial to communicate the subsalt source rocks and the upper reservoirs,and to facilitate the formation of the shallow reservoirs in this area.