Prediction of pore pressure and fracture pressure in Cauvery and Krishna-Godavari basins, India

Abstract Geoscientific data from several wells drilled in onshore and offshore parts of the Cauvery and Krishna-Godavari basins, two main hydrocarbon producing basins located in the east coast of India, have been used to determine pore pressures and fracture pressures in the subsurface formations. We have estimated pore pressure based on Zhang's porosity model. Variations of normal compaction curves across the basins are demonstrated here. This study also proposes simple relationships among the parameters used in Eaton's equation for estimating the fracture pressure. Relations established based on the available data in this current study are compressional and shear sonic velocities against bulk density, Poisson's ratio against depth, and the overburden stress against depth. These empirical relationships can be used to predict fracture gradient for the future drilling locations in these basins. The pore pressure in Cauvery basin is shown to be almost hydrostatic in nature, which is due to normal sedimentation rate. High sedimentation rate in the Miocene section of the KG basin is found to be the main reason for overpressure development.