Simulation of ground stress field and fracture anticipation with effect of pore pressure

Abstract

Triaxial compression tests are carried out on the cores with different confining pressure and pore pressure to study the rupture mode and fracture distribution of carbonate rocks in Kenkiyak pre-salt oilfield, and the cores are made into thin sections after experiment. It shows that shear plane, high angle crack, conjugate shear cracks and net fractures will gradually appear with the effective confining pressure, the rock texture is damaged more and more seriously with the increase of effective confining pressure. Tectonic stress field in Kenkiyak Field is simulated by finite element numerical simulation software ADINA considering the effect of pore pressure, this model contains five faults and assumes that two planes of faults could slip with the force to decompress. The simulation results indicate that the total displacement coincides with the practical formation, the simulated tectonic stress fits with the values measured by acoustic emission testing, and the direction of major horizontal principal stress is consistent with the imaging log interpretation data. The fracture rupture rate and density are predicted according to tension and shear rupture rate which derived by simulation results. The fracture density varies widely in the simulated region and cracks develop easily on the structural high position, near the fault because of the increasing pore pressure and extrusion in the process of the tectonic movements.