陆相断陷盆地相-势耦合控藏作用及其基本模式

Control of facies-potential coupling on hydrocarbon accumulation in continental faulted basins and its basic geological models

陆相断陷盆地油气运移、富集具有"断坡控砂、复式输导、相势控藏"的基本特征。文中以渤海湾盆地东营凹陷为例,详细阐述了"相""势"控藏特征和"优相-低势耦合控藏"的基本模式。研究表明,"相"控油气作用可分4个层次,即构造相控油气作用、沉积相控油气作用、岩相控油气作用和岩石物理相控油气作用,它们反映了从宏观到微观的油气分布规律和富集机制。"相"控油气作用的基本模式为"高孔-优相控藏"。"势"控油气作用可分为4种类型,即位能控油气作用、压能控油气作用、界面能控油气作用和动能控油气作用。不同类型势能控制着不同类型油气藏的形成和富集。"势"控油气作用的基本模式为"低势控藏"。优相-低势耦合作用控制了东营凹陷90%以上的油气藏分布,决定了不同类型的油气藏在不同埋深条件下的分布及势能差异,解释了主要目的层有效储层临界孔隙度随埋深增大而变小的规律性,阐明了各类圈闭内部势能较外部势能低50%以上才能开始聚集油气的机制。应用"近源-优相-低势"控藏模式可以对陆相断陷盆地潜在隐蔽油气藏进行分布预测。

Hydrocarbon migration and accumulation in continental faulted basins feature in ＂fault-slope controlling sand, multiple hydrocarbon transporting system, sedimentary facies and fluid potentials jointly controlling hydrocarbon accumulation＂. Taking the Dongying Sag in the Bohaiwan Basin as an example, this article expounds on the characteristics of facies-potential controlled reservoiring and the basic geological model of ＂dominant facies-low potential coupling controlled reservoiring＂. The research shows that the controlling effects of sedimentary facies on hydrocarbon accumulation can be divided into four categories： structural facies, sedimentary facies,lithologic facies, and petrophysical facies. They reflect hydrocarbon distribution and accumulation model from macro to micro perspectives. The basic geological mode of facies controlled hydrocarbon accumulation is ＂high porosity and dominant facies＂. While fluid potential control over oil and gas accumulation can be divided into the following four types, namely geopotential energy, pressure energy, interracial energy, and hydrodynamic energy. These four types of potentials control the formation and distribution of different reservoirs with a basic geological model of ＂low potential controlled hydrocarbon accumulation＂. The coupling of dominant facies and low potential control more than 90% of the discovered hydrocarbon accumulations in the the Dongying Sag and determine me distributions and potential energy differences of different types of oil/gas reservoirs with different burial depth, and helps to explain the decreasing trend of the threshold porosity of effective reservoirs with the increasing burial depth and to illustrate the mechanism that hydrocarbons can accumulate only when the internal potential of a trap being less than a half of the external potential. The reservoiring controlling model of ＂near source kitchen, dominant facies and low potential＂ can be applied in predicting the distributions of subtle oil and gas reservoirs in continental faulted basins.