In-Situ Stress State and Geomechanical Modeling of the Paleozoic Clastic Reservoirs in Hassi Terfa Field, Algeria

ABSTRACT: This study presents a comprehensive geomechanical modeling of the Cambro-Ordovician clastic reservoir interval from Hassi Terfa field, Algeria. Wireline logs, direct downhole measurements and drilling data have been integrated for the work. The acoustic image log analysis exhibits B-Quality breakouts with a cumulative breakout length of 55m. These breakouts indicate a mean maximum horizontal stress orientation of N114˚E±7.6˚. The breakout width ranges between 25˚-89˚. Based on the regional microfrac data, we infer a minimum horizontal stress gradient between 0.8-0.9 psi/ft. SHMax gradient has been constrained from the breakout width using stress polygon approach. A mean breakout width of 53.77˚ translates to a SHMax gradient range of 1.2-1.6 psi/ft. The relative magnitudes of the principal stresses indicate a strong strike-slip tectonic stress state with a SHmax/Shmin ratio of 1.6 within the Paleozoic interval. A good match between observed and modelled breakout widths validates the inferences about the in-situ stress gradients and thus provides an excellent calibration of the geomechanical model. 1. INTRODUCTION Geomechanics plays a critical role in optimizing the drilling trajectory, fluid injection, and production enhancement (Almalikee and Sen, 2021, 2022; Leila et al., 2021; Alabere et al., 2022; Baouche et al., 2022a; Farouk et al., 2022; Sen et al., 2024a). Comprehensive geomechanical modeling provides the rock-mechanical properties, in-situ stress gradients and horizontal stress orientations. This study focuses on the Cambro-Ordovician clastic reservoir interval of the Hassi Terfa field, located in the central Saharan platform of Algeria. The studied field is a fault-compartmentalized oil pool along the N-S to NE-SW trending Amguid-Hassi Messaoud structure of the Algerian Sahara. The objectives of this study were to: i) estimate the rock-mechanical properties, ii) interpret horizontal stress azimuth from wellbore compressive failures, and iii) infer pore pressure and in-situ stress gradients. We have integrated wireline logs, acoustic image logs, downhole measurements, and drilling data to establish a well constrained and calibrated 1D geomechanical model.