低密度浊流的沉积成因及控制因素 --以东营凹陷广利油田纯化镇组为例

低密度浊流作为重力流向牵引流演变的过渡流体,其沉积物颗粒的支撑机制、搬运方式在不同沉积演化阶段具有不同的特点,沉积形成的砂岩在矿物成分、颗粒大小、分选特征以及沉积结构等方面变化较大。从沉积物重力流成因机制的角度分析了低密度浊流流体性质的演化规律;针对低密度浊流沉积的特点,提出了按岩石类型分析砂岩沉积结构的方法。根据低密度浊流的理论研究成果、沉积物颗粒的搬运方式及其沉积序列实例综合分析,指出低密度浊流首先体现出紊流的性质,沉积混合砂岩,粒度概率累积曲线呈向上凸的弧形;然后沉积不等粒砂岩;最终演变为牵引流,沉积细砂岩、粉砂岩等细粒岩石,粒度概率累积曲线主要呈两段式。文章总结了低密度浊流的主要沉积特征及其形成的控制因素。

Sedimentary genesis and controlling factors on low -density turbidity currents--taking Chunhnazhen formation of Guangli Oilfield, Dongying Sag as example

Low - density turbidity current is a transition flow evolved from gravity flow to drag flow,whose supporting mechanism and transporting way of the sedimentary grains have different characteristics in the different stages of sedimentary evolution process, so the mineral components, grain sizes, sorting characteristic, depositional textures,etc. of the sandstones originated by sedimentation varied extensively. The evolution law of fluid properties of low - density turbidity currents was analyzed from the genesis mechanism of gravity flow. Aiming at the sedimentary features of the low - density turbidity currents, a method of analyzing sedimentary textures of sandstones in terms of rock types was provided . Based on the comprehensive analysis of the theoretical studies, transportation way of sedimentary grains and the example of sedimentary succession of the low -density turbidity currents, it has been pointed out that low - density turbidity current exhibited firstly turbulent feature and hybrid sandstone whose cumulative grain - size distribution curve is in the shape of convex ; and then inequigranular sandstone was deposited; finally drag flow with sedimentary fine sandstone and siltstone was evolved, whose cumulative grain - size distribution curve is in the shape of two - segment. The principal sedimentary characteristics and their controlling factors of the low - density turbidity currents were summarized.