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, the studies on this mechanism have been done qualitatively. By using numerical basin model based on finite element method, the pressuring effect of tectonic stress in sedimentary formations was simulated. On a one‐dimensional profile, the strength of tectonic stress, the duration and pattern of tectonic action, the physical diagenesis characteristics of formations, as well as intrinsic permeability, were taken as principal factors that influence overpressure generating and maintaining. Some new understandings on tectonic stress leading mechanism were proposed: (1) the tectonic stress may be considered as one kind of loading that acts on 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.