构造应力场对油气运移的影响

Influence of tectonic stress on hydrocarbon migration.

油气是一种流体，其运动遵循流体力学基本原理，其作用空间是多孔介质，因而介质的应力状态是影响油气运移的一项重要因素。应用流体力学、渗流力学、岩土力学及弹性力学的理论及方法，分析了考虑三维应力状态下可变形介质中流体运移的动力学方程。由该方程可以看出，应力状态通过３方面影响油气运移的特征：①应力的作用改变介质的渗透性能；②平均正应力的变化速率是流体运移的一个驱动力（它以源汇项形式反映在方程中）；③应力的作用改变流体的定解条件，即影响流场的初始状态和边界状态。构造应力场对流体运移的总体影响是这３方面作用的综合。依据该思路提出了一个油气运移模型，并据某油田的地质条件及构造背景选取计算参数，采用有限元方法进行实例模拟；计算结果表明，在其它条件完全相同的情况下，地质体的应力状态改变，油气运移的特征发生相应变化。图２参１２（王孝陵摘）

Hydrocarbon is one kind of fluid. Its migration in porous media whose stress feature is an important factor influencing hydrocarbon migration, complies with the fundamental principle of hydrodynamics. By means of theories and methods in fluid mechanics, flow mechanics, rock mechanics and elastic mechanics, the dynamicequation of fluid migration in shapeless media under confining stress is analyzed, from it can be seen that stress feature has three fold effects on hydrocarbon migration, which are: ①the stress can change the permeability of media, ②the change rate of the mean principal compressive stress supplies a driving force for the flow of fluid and, ③the stress affects the initial and boundary conditions. Hydrocarbon migration is a complicated process, in which many factors may affect it besides the tectonic stress field. It is more likely the combination results of multiple factors. Based on the parameters chosen according to the geology and structural setting of an oil field, a practical case simulation was made by using finite element method, which indicates that changing the stress feature of a geological body, its HC migration characters would be changed as well.