一种新型圈闭:断控缝洞型圈闭

A new trap type:Fault-controlled fracture-vuggy trap

近年来,中国石化西北油田分公司在塔里木盆地顺托果勒低隆起超深层碳酸盐岩中发现了10×10^(8)t级油气田——顺北油气田。顺北油气田的圈闭为新发现的断控缝洞型圈闭。在走滑断裂作用下,顺北地区中-下奥陶统碳酸盐岩地层因构造破裂产生了大量裂缝、孔洞与洞穴,形成了沿走滑断裂带展布的碳酸盐岩缝洞型储集体。这些储集体在上覆泥质岩区域盖层和致密碳酸盐岩局部盖层封挡条件下,形成了断控缝洞型圈闭。根据走滑断裂构造样式、破碎程度和内部储层分布特征等控制因素分析,将断控缝洞型圈闭划分为压扭型、平移型、张扭型及复合型等4个亚类。断控缝洞型圈闭的发现进一步丰富了海相碳酸盐岩油气成藏理论,为深层-超深层碳酸盐岩领域油气勘探开发提供了科学依据。

Sinopec Northwest Oilfield Company recently struck a billion ton-scale oil/gas discovery-the Shunbei oil and gas field-in the deep carbonates of Shuntuoguole low-uplift,Tarim Basin.A new trap type-fault-controlled fracturevuggy trap-is found to be the major container for oil and gas in the field.Analyses show that the traps take the fracturevuggy layers along strike-slip fault zone as reservoirs and the overlying mudstone and local tight carbonates as caprocks.The reservoirs are probably the result of a tectonic disruption of the Middle-Lower Ordovician carbonates under strikeslip faulting that induced the formation of a large number of fractures,vugs and caverns.Based on the style and fragmentation of strike-slip faults as well as the distribution of internal reservoirs in the field,this study classifies the traps into four sub-types:transpression type,translation type,transtension type and composite type.This new type of trap further enriches the theory of marine carbonate reservoirs for oil and gas and provides a scientific basis for future exploration and development in deep and ultra-deep carbonates.