火山碎屑沉积物是油气的重要储层

Pyroclastic deposits:an important reservoir for hydrocarbon accumulation

火山碎屑沉积物是重要的油气储层。火山碎屑沉积按成因划分为火山喷发空中降落堆积物、火山碎屑流状堆积物、火山泥流堆积物和火山基浪堆积物等。它们的特征和储层潜能是不同的。火山碎屑沉积物的识别和解释能够极大的影响火山碎屑层序的勘探方法、储油层几何形态和性能的预测。美国亚利桑那洲早侏罗世怀特申组是一个多喷发火山口复合体,把不同成因类型的火山碎屑堆积物和熔岩分为4个相:火口相、近火口相、中间相和远端相。讨论了这些相对储层性能的影响。火山碎屑大部分由化学性活泼的和不稳定矿物组成,在埋藏成岩期间具有迅速和广泛的变化。火山碎屑的赋存,有助于溶解孔隙的发育,能够增强储油层性能。

Pyroclastic deposits are important reservoirs and can be divided into fallout tephradeposits,pyroclastic flow deposits,lahar deposits and base surge deposits by their genesis. The four kinds of pyroclastic deposits have different reservoir characteristics and potential. The identification and interpretation of the pyroclastic deposits can significantly influence the exploration methods of volcaniclastic sequences and the prediction of reservoir ge- ometry and quality. The Lower Jurassic Wrightson Formation in Arizona is a multi-crater complex. Its pyroclastic deposits and lavas with various genesis can be divided into crater, proximal, middle and distal facies. The influ- ences of these facies on reservoir quality are discussed. Volcanic clasts are mostly composed of chemically active and unstable minerals that can change rapidly and extensively during burial diagenesis. The occurrence of vol- canic clasts may contribute to the development of dissolution porosity which can enhance reservoir quality.