PRESSURE AND TEMPERATURE EVOLUTION IN SEDIMENTARY BASINS

This article is about what influence continuous sedimentation has on the excess pressure, compaction and temperature in a sedimentary basin. We give an answer in terms of two dimensionless numbers LAMBDA-0 and LAMBDA-1, which characterize the pressure and the temperature solution respectively. LAMBDA-1 = 1 is shown to define a transitional zone between excess pressured basins (with low compaction) and hydrostatic basins (with high compaction). The LAMBDA-0 parameter generalizes earlier results of Gibson. The most important physical parameter in LAMBDA-0 is the ratio between the permeability and the sedimentation rate. By means of LAMBDA-0 we can quantify when 'high' sedimentation rates and 'low' permeability yield high excess pressures. This analysis is based on the porosity given by formulae of the form phi = phi(alpha-p(s)), where p(s) is the effective stress, and alpha is some scaling factor. In an analogous manner, LAMBDA-1 = 1 defines a transitional zone when moving boundary effects become marked on the temperature. The most important parameter in LAMBDA-1 is the ratio between alpha and the sedimentation rate. Simulation results are obtained by solving dimensionless pressure and temperature equations. The numerical pressure solution is compared with the exact solution given by Gibson, and is shown to be in excellent accordance.