构造应力超压机制的定量分析

构造应力一直被认为是超压形成的重要机制，但对其研究还处于定性的分析阶段．本文利用以有限元方法为基础的盆地数值模型，在一维的剖面上考虑构造应力强度、构造作用时间及方式、地层的物理成岩特征及其岩石渗透率等因素的变化，对构造应力在地层压力演化中的作用进行了模拟分析．获得了一些构造应力作为超压形成机制的新认识：（1）构造应力在水平方向上增加了地层的压实作用；（2）在极端条件下，构造应力所引起的超压增量可达构造应力的一半；（3）上覆地层因构造应力的作用而发生的更为强烈的压实结果对其下伏地层内压力的演化也很重要，其增加的超压增量可达构造应力的15%～20％．

QUANTITATIVE ANALYSIS ON OVERPRESSURING MECHANISM RESULTED FROM TECTONIC STRESS

Tectonic stress have long time been considered as one of the most important overpressuring mechanisms．However，previous studies on this mechanism have been done in a qualitative way．By using numerical basin model based on the finite element method，the pressuring effect of tectonic stress in sedimentary formations is simulated．On a one dimension profile，the strength of tectonic stress，the duration and pattern of tectonic action，the physical diagenesis characteristics of formations，as well as intrinsic permeability，are taken as principal factors that influence overpressure generating and maintaining．Some new understandings on tectonic stress leading mechanism are proposed： 1) The tectonic stress may be considered as one kind of load that acts in horizontal direction to accelerate formation compaction．2) Under well sealing conditions，the overpressure increment resulted from tectonic stress may reach to half of the tectonic stress acting on sediments．3)Because of tectonic stress，the compensated compaction within overlying formations may increase the compaction of underlying formations，and result in about 15％～20％ pressure increment．