摘要
裂缝是低渗透储层流体流动的主要通道,控制了低渗透油气藏的渗流系统。低渗透储层裂缝的形成与流体密切相关,高流体压力引起岩石内部的有效正应力下降,导致岩石剪切破裂强度下降,使岩石容易产生裂缝。高孔隙流体压力还造成某一点的应力摩尔圆向左移动,可以使其最小主应力(σ3)由压应力状态变成拉张应力状态,从而在岩石中形成拉张裂缝。裂缝的渗透性受现今应力场的影响,通常与现今应力场最大主压应力近平行分布的裂缝呈拉张状态,连通性好,开度大,渗透率高,是主渗透裂缝方向。构造应力对沉积盆地流体流动的影响主要表现在三个方面:(1)构造应力导致的岩石变形,不仅提供了流体流动的通道,而且还改变了岩石的渗透性能;(2)在构造强烈活动时期,构造应力的快速变化是流体流动的重要驱动力;(3)岩石中应力状态影响多孔介质的有效应力,从而影响介质中的渗流场。当作用在含流体介质上的构造应力发生改变时,岩石孔隙体积变小,构造应力首先由岩石的骨架来承担;当岩石孔隙体积减小到一定程度时,构造应力由孔隙流体来承担,从而影响岩层渗流场的变化。
Fractures are the main channel for fluid flow and control the seepage system of the low-permeability reservoirs. The formation of fractures is related to fluid. High-pressure fluids may cause the fall of inner effective stress of rock and the reduction of rock shear strength; therefore, fractures are easily formed in the rock. High-pressure pore fluids may also make the stress Mohr circle move from right to left, and the minimum principal stress （σ2） change from the compressive stress state to the tensional stress state; and may form tensional fractures in the compressive structural circumstance. The seepage of fracture is affected by the present-day stress field. Usually, fractures approximately parallel to the maximum principal compressive stress are ten- sional, have good connectivity, big aperture, and high permeability, and are the main seepage fractures. The influence of tectonic stress on fluid flow in sedimentary basins are mainly in three aspects. Firstly, rock deformation caused by tectonic stress not only provides the flow channel for fluid but also changes the penetrability of rocks. Secondly, at the period of strong tectonic movement, the rapid change of tectonic stress is an important driving power for fluid flow. Finally, tectonic stress may influence the seepage field through its influence on the effective stress. When the tectonic stress changes, rock pore bulk will diminish and the tectonic stress is borne by rock grains first and then turned into structure stress. When the rock pore bulk is diminished to a certain degree, the tectonic stress is mainly borne by pore fluids, which affects the charge of seepage field in the terrane.
出处
《地学前缘》
CSCD
北大核心
2008年第3期292-298,共7页
Earth Science Frontiers
基金
教育部新世纪优秀人才支持计划项目
中国石油天然气股份有限公司科技风险创新基金项目(07-06D-01-04-01-08)
国家自然科学基金资助项目(40572080)
关键词
裂缝
流体
构造应力
低渗透储层
fracture
florid
tectonic stress
low-permeability reservoir
作者简介
曾联波(1967-)，男．博士，教授，主要从事油气构造地质学研究。E-mail：lbzeng@sina．com.
