山东东营凹陷前古近系水化学场、水动力场与油气成藏

东营凹陷前古近系水化学特征对沉积环境有着良好的响应,从太古宙到早古生代的寒武纪,由于海水的侵入,使矿化度和氯离子含量出现增大的物质响应,但从奥陶纪到中生代,构造作用变强,水深总体变浅,保存环境变差,矿化度和氯离子含量总体降低。水化学剖面具有一定的分带性,大致可以划分为3种水文环境:水文流畅带(0~1.1km)、水文阻滞过渡带(1.1~1.75 km)和水文迟缓带(>1.75 km)。在各带矿化度、主要离子含量及离子组合系数等水化学参数具有不同的响应,其中水文阻滞过渡带和水文迟缓带对油气成藏有利。主要发育CaC l2型水和NaHCO3型水,随着矿化度的升高,NaHCO3型水逐渐被CaC l2型水取代。前古近系水动力场具有一定的对称性,从太古宙到中生代,水动力场中心和水动力场对称轴线发生变化。盆地内部发育以离心流为主的水动力场,在盆地边缘发育以向心流为主的水动力场,在离心流与向心流相接触的离心流泄水地带是油气聚集成藏的有利位置。

Formation Water Chemical and Hydrodynamic Fields and Their Relations to the Hydrocarbon Accumulation in the Pre-Tertiary of Dongying Depression, Shandong

The formation water chemical characteristics in the pre-Tertiary had good response to the sedimentary conditions in Dongying Depression.The contents of total salinity and chloride ion increased from the Archean to the Cambrian in the Lower Paleozoic for the invasion of sea water,and decreased from the Ordovician to the Mesozoic with the stronger tectonic movement and the worsen conservation environment.The vertical distributions of the formation water chemical and dynamical belts have obvious zoning features.According to the vertical characteristics of the formation water,three hydrological environments can be divided: formation water frequency alternation belt(0-1.1 km),formation water alternate blocking belt(1.1-1.75 km)and formation water alternate tardy belt(>1.75 km).In every belt,the total salinities,ions and ion composition ratios have different responses to strata,and the blocking belt and the tardy belt were favorable for hydrocarbon accumulation.There mainly developed CaCl2 type water and NaHCO3 type water,and the NaHCO3 type water was substituted by the CaCl2 type water with the content of total salinity increasing.The hydrodynamic field of the pre-Tertiary in Dongying Depression had characteristics of symmetry,and from the Archean to the Mesozoic the center of the hydrodynamic field and the symmetrical axial line changed.The hydrodynamic field in the central depression was controlled by centrifugal flow,and the hydrodynamic field in the boundary of the basin was mainly dominated by endocentric flow,and in the sluicing positions of the centrifugal flow in contacting region by the centrifugal flow and endocentric flow were the favorable targets for hydrocarbon accumulation.