塔东地区震旦系白云岩成因及储层发育模式

Genesis mechanism and reservoir model of Sinian dolomite in eastern Tarim area

塔东地区震旦系顶部发育一套稳定分布的白云岩,厚度在24~799 m。目前,对于这套白云岩的储层特征、成因机制和控制因素尚未形成统一认识,制约了塔东地区震旦系的勘探突破。文中利用钻井、岩心、薄片鉴定和地球化学等数据,分析了震旦系白云岩的储层特征、成因机制及有利储层控制因素。结果表明:塔东地区震旦系白云岩为一套碳酸盐台地相-缓坡相沉积产物,依据岩石结构特征及成因机制可以划分为结晶白云岩、颗粒白云岩和微生物白云岩三大类岩石类型;白云岩成因主要为准同生期海水成岩模式和埋藏成岩模式,2种成因白云岩在纵向上可区分;震旦系白云岩储层发育受沉积相带、热液及构造作用3个因素控制,3种控制作用也不同程度地影响了白云岩化的机制。

A set of dolomite with stable distribution developed at the top of Sinian system in the eastern Tarim area, and the thickness is between 24-799 m. So far, the characteristics and genesis mechanism of the dolomite reservoir have not been unified, which restricts the exploration breakthrough in this area. This paper, by using drilling, core, thin section observation and rock geochemistry data, summarizes Sinian dolomite reservoir characteristics, genesis mechanism and favorable reservoir control factors in the eastern Tarim area. The results show that the Sinian dolomite of eastern Tarim area is a set of carbonate platform facies and gentle slope facies. According to the characteristics of rock structure and genetic mechanism, it can be divided into crystalline dolomite, granular dolomite and microbial dolomite. It shall be divided into penecontemporaneous briny diagenesis and burial diagenetic mode. The two modes can be distinguished vertically, the upper part of the Sinian dolomite is the penecontemporaneous briny diagenetic dolomite, and the lower part of the Sinian dolomite is the buried diagenetic dolomite. The development of Sinian dolomite reservoir is controlled by sedimentary facies, hydrothermal fluid and tectonic processes, which also influence the dolomization mechanism with varying degrees.