陆相断陷盆地相控油气特征及其基本模式

Characteristics and basic model of facies controlling oil and gas in continental fault basin

地质相是沉积地层内沉积物(岩)形成条件的物质表现,由宏观到微观分为4个层次,即构造相、沉积相、岩石相和岩石物理相。不同层次地质相的控油气作用具有不同形式的表现。研究表明,陆相断陷盆地内不同的构造单元、不同的沉积相控制着不同类型油气藏的形成与分布;不同的构造单元和不同的沉积相的储油气层的临界孔隙度和渗透率随埋藏深度增大而降低;在不考虑构造和沉积相背景条件下,不能依据地层的绝对孔渗条件判别和评价有效储集层。沉积颗粒不粗不细的优相砂岩类地层控制着油气的富集成藏;相同背景条件下相对高孔渗的储集层控制着油气的富集成藏。优相与相对高孔渗控藏是相控油气作用的基本模式。利用相控油气作用的基本模式可以预测有利成藏领域。

Geofacies are the material expression of the conditions to form sediments（sedimentary rock）in sedimentary formation.Geofacies are divided into four hierarchies from macro-to micro-perspectives,namely structural facies,sedimentary facies,lithologic facies and petrophysical facies.The hydrocarbon control function of the geofacies in different hierarchies exhibits differently.According to this research,different tectonic units and sedimentary facies in a terrestrial rifted basin control the formation and distribution of different types of hydrocarbon reservoir;the critical porosity and permeability of hydrocarbon reservoir of different tectonic units and sedimentary facies decrease as the buried depth increases;without considering the background conditions of tectonic and sedimentary facies,it is impossible to determine and evaluate the effective reservoirs according to the absolute conditions of porosity and permeability.Sand rock strata with well-sized sediment grain and favorable facies control the accumulation of oil and gas,while under the same conditions,reservoirs with relatively high porosity and permeability control the accumulation of oil and gas.Reservoir control with favorable facies and relatively high porosity and permeability is the basic control pattern of facies-controlled hydrocarbon accumulation,which can be used to forecast the favorable area for hydrocarbon accumulation.