麦盖提斜坡奥陶系热液溶蚀流体对内幕白云岩储层的改造作用

摘要

High-quality hydrothermal karst reservoirs are well developed in the Ordovician dolomite of Maigaiti slope in Tarim Basin.The reservoirs feature in karst fractures and cavities filled with saddle dolomite and hydrothermal minerals such as quartz,pyrite,celestineand siliceous and etc.,and their physical properties were greatly improved by inter-crystal pores and dissolved pores formed during hydrothermal karst activities.Analyses of faults in the research area were com-bined with drilling data to study faulting activities associated with deep hydrothermal fluids and their effect on the trans-formation of dolomite reservoirs and characterize hydrothermol fluid on profiles.The results show that multi-staged deep and giant fault zones like Qunkuqiake fault zone,Mazatage fault zone and Madong thrust belt in the research area,were perfect places for hydrothermal fluid activities.Areas far from the fault zones and small extentional strike-slip faults may serve as the pathways for the fluids to flow by,and dolomite reservoirs presented themselves as a string of beads on seis-mic profiles and widely-distributed dots on the plane.Based on the above observation and reservoirsing conditions of the area,we suggest that the dolomite reservoirs in Qunkuqiake fault zone have the potential to be practical exploration targets and widely-distributed dolomite reservoirs controlled by tensional-shear faults in the area shall also be future exploration targets.%塔里木盆地麦盖提斜坡奥陶系深部白云岩发育优质热液溶蚀储层，主要特征有：①岩溶孔洞、缝充填鞍状白云石以及石英、黄铁矿、天青石、硅质充填等热液矿物；②热液溶蚀作用形成的溶蚀孔洞明显改善了白云岩储层物性。通过研究区断裂性质分析，结合钻井热液溶蚀特征，对与深部热流体相匹配的断裂活动特征及对白云岩储层的改造作用进行研究，探讨了热液流体在剖面上的活动特征。研究认为，多期活动的深大断裂带有利于埋藏热液流体活动，研究区群苦恰克断裂带、玛扎塔格断裂带以及玛东冲断带均是热液白云岩储层发育有利区；远离断裂带的广大区域，二叠纪小型张性走滑断裂同样可以作为热液流体活动的运移通道，形成的白云岩储层在地震剖面上表现为“串珠”状，平面上呈星点状大面积分布。结合研究区油气成藏条件分析，认为群苦恰克断裂带的热液白云岩储层是斜坡区较为现实的勘探领域；受控于小型张扭断裂的白云岩储层分布面积广，资源潜力大，具有较好的勘探前景。