Comprehensive mechanical earth modeling using well data

Abstract

Mechanical earth model is a numerical representation of the stress state, pore pressure and rock mechanical properties. While the different parameters in the MEM are interconnected in various ways, they fundamentally stem from the same basic set of log measurements. This paper demonstrates a scientific workflow to build a comprehensive well-centric MEM for a well in a carbonate reservoir in Persian Gulf and calibrate it via utilizing the existing data including LOT, MDT, drilling incidents, etc., to minimize the uncertainties related to data limitations. Finally, the calibrated MEM was used for sensitivity analysis of various wellbore trajectories and mud weight/pressure window for planning future wells and safe drilling in this underdevelopment field. Poroelastic modeling along with rigorous calibration indicates strike slip toward normal faulting stress regime. Also, shear wave anisotropy analysis results in N40E orientation for the maximum horizontal stress. The optimum mud weight for safe drilling was found to be 120 pcf for Gachsaran Formation, 105 pcf for all the formations from Asmari to Kazhdumi limestone and 85 pcf for all the formations from Yamama to total depth. On this basis, it is recommended to put the casing shoes at the base of Gachsaran, Kazhdumi limestone and final depth. The results recommend planning the future wells horizontally in the NE–SW direction for formations having SS stress regime and wells near vertically in formations having NF stress regime. Besides, the drilling safe mud window resulting from Mogi–Coulomb failure criterion is broader, while the Mohr–Coulomb is more limited.