油气优势运移通道的类型及其物理模拟实验研究

Research on types of the dominant migration pathways and their physical simulation experiments

地质分析和物理模拟实验证实地质条件下油气总是沿着浮力最大和阻力最小的的方向和通道运移,形成油气优势运移通道有5种基本模式:级差优势、分隔优势、流向优势、流压优势和断面优势.物理模拟实验结果表明油气运移实际通道只占输导层的1%～10%,但却运输了油气的绝大部分;输导层物性的差异、盖层沉降中心的偏移、流体动力、断层倾角及断层面几何形态控制了油气运移的优势通道;实际地质条件下油气运移所形成的优势通道是上述5种模式综合作用的结果.由于优势通道是大部分油气运移的实际路径,其研究对追踪油气来源、预测有利圈闭有着十分重要的作用.

Geological analysis and physical simulation experiments confirm that, under geological conditions, hydrocarbon tends to migrate along a path of least resistance and follow the largest buoyancy. The dominant migration pathway includes mainly five models： first, hydrocarbons tends to migrate along the pathways with high porosity and permeability, and with a large grade difference relative to surrounding rocks （grade difference predominance） ; second,hydrocarbon tends to migrate towards to the direction opposite to excursion of caprock sedimentation center （divided trough predominance）; third, hydrocarbons tends to migrate in the direc- tion of lower fluid pressure （fluid pressure predominance）; fourth, hydrocarbons tends to migrate in the direction vertical to buoyancy （flow direction predominance）; last, hydrocarbons tends to migrate in the direction with a large grade reduce of liquid potential and least resistence of fault section （fault section predominance）. Natural dominant pathway of most oil and gas migration could be influenced by the five modes above. The result of physical simulation experiments indicates that the migration pathway transporting the majority of hydro- carbon accounts for only 1% to 10% of the whole carrier bed. The dominant migration pathway is controlled comprehensively by physical property difference of carrier bed, excursion of sedimentation center of caprocks, fluid dynamics, fault obliquity, and form of fault section. Because the dominant migration pathway is preferred by the majority of oil and gas on actual geological condition, the research on it is very important for predicting hydrocarbon sources and favorable traps.