Geomechanical modeling using finite element method for prediction of in-situ stress in Krishna–Godavari basin, India

Abstract

This study provides quantitative rock mechanical properties and analyses of in-situ stress and pore pressure in several oil/gas fields of East and West Godavari sub-basins. High pore pressure gradients varying from 11.85 to 12.80MPa/km exist within these oil/gas fields. Vertical stress (SV) gradients in the range 21.00 to 22.85MPa/km are seen to exist. Minimum horizontal principal stress (Sh) magnitude is found to vary from 64% to 76% of SV, while maximum horizontal principal stress (SH) magnitude is observed to vary from 90% to 92% of SV within normally pressured to over-pressured sediments. The breakout derived SH orientation from two well varies from N14°E to N22.5°E in the Krishna–Godavari basin. Rock mechanical properties such as Young’s modulus, Poisson’s ratio and unconfined compressive strength have been estimated from logs of compressional and shear wave travel time. Two-dimensional (2D) stress modeling using finite element analysis has been carried out for some important oil/gas fields situated within East and West Godavari sub-basins as a part of the current study. Regional SH orientation has been used for application of stress at the model boundary. Discontinuities in the stress pattern which can be associated with interfaces between weak and competent layers have been commonly observed and especially where silici-clastic and volcanic inter-bedded sequences are encountered. The model predicted stress orientations are verified with the Formation Micro Imager (FMI) log data of wells at the above-mentioned sub-basins.