Contributions of Compaction and Aquathermal Pressuring to Geopressure and the Influence of Environmental Conditions

Abnormal geopressure results from disequilibrium between excess fluid, which must be removed to maintain normal compaction, and the fluid expelling capacity of sediments. The effects of two factors affecting geopressure, namely compaction and aquathermal pressuring, are studied using a hydrodynamic model based on the solution of simultaneous equations (mainly Darcy’s law and Athy’s porosity-depth relationship). Geopressures are computed on a one-dimensional sediment profile and based on four environments that may significantly influence the excess pore-fluid volume and the permeability of sediments. The quantitative excess analysis demonstrates that in actual geologic environments, the aquathermal factor has no practical significance in abnormal pressure occurrence.