川东北通南巴构造带须家河组裂缝特征

Characteristics of Fractures in Xujiahe Formation of Tongnanba Structural Belt,Northeastern Sichuan Basin

为了研究裂缝对致密砂岩储集层的改造特征及其对天然气成藏的影响,以四川盆地东北部通南巴构造带为例,利用岩心、薄片及成像测井等资料,对研究区须家河组裂缝发育特征进行综合分析。研究区须家河组致密砂岩裂缝按成因可划分为断层相关裂缝、褶皱相关裂缝、顺层滑脱裂缝和砾石相关裂缝,其中断层相关裂缝与褶皱相关裂缝是主要的有效裂缝。研究区有效裂缝的发育与岩性、断裂和局部构造相关性明显,在细砂岩与中砂岩中最为发育,高曲率背斜与大断裂是裂缝发育的有利条件。研究区须家河组致密砂岩裂缝的发育受晚侏罗世以来盆缘造山活动的影响,此时研究区须家河组储集层已经致密,裂缝的发育提高了储集层的储渗性,对研究区晚期气藏的形成和高产具有重要意义。

In order to study the characteristics of fractures in the tight sandstone reservoirs and their influences on natural gas accumula-tion, taking Tongnanba structural belt as a case, the paper comprehensively studies the fracture development characteristics in Xujiahe for-mation in the study area by using the data of core, thin section and FMI logging. According to fracture genesis, the fractures in the tightsandstone reservoir of Xujiahe formation can be classified into 4 types, namely fault-associated fracture, fold-associated fracture, slidingfracture and gravel-associated fracture, among which fault-associated and fold-associated fractures are the main effective fractures. Goodcorrelations among the development of effective fractures, lithology, fault and local structures are found in the study area. Fractures aremost developed in the fine sandstones and medium-sized sandstones, and high-curvature anticline and large fracture are favorable condi-tions for fracture development in the study area. Fracture development in the tight sandstone reservoir of Xujiahe formation was controlledby orogenic activities in the basin margin since Late Jurassic during which the reservoir of Xujiahe formation was densified and the develop-ment of fractures improved the reservoir quality and permeability which had important significance for accumulation and high-yield of thegas reservoirs formed at the late stage.Sichuan basin; Tongnanba structural belt; Xujiahe formation; tight sandstone; fracture characteristic; forming mechanism