Characterization of Maximum Horizontal Stress from Wellbore Failures – A Case Study from the Tight Paleozoic Hamra Quartzite Oil Reservoir of Oued Mya Basin, Algeria

Abstract

Abstract The Cambro-Ordovician Hamra Quartzite Formation is one of the important reservoirs from Algerian Sahara. The objectives of this study were to characterize the wellbore breakouts and constrain the maximum horizontal stress (Shmax) based on the inferred compressive failures within the Paleozoic reservoir. A-Quality breakouts were deciphered within the reservoir interval from a cumulative of 138m of acoustic image log indicating a mean SHmax orientation of N118˚E±8˚. Interpreted breakout widths exhibit a range between 32.6˚ and 90.81˚, which indicated a SHmax range of 24.4-34.7 MPa/km. The average breakout width of 62.58˚ translates to a SHmax gradient range of 27.2 and 31.2 MPa/km. The relative magnitudes of the principal stresses indicate a strong strike-slip tectonic stress state with a SHmax/Shmin ratio of 1.41-1.81 within the Ordovician interval. Following the frictional faulting-based stress polygon approach, measurement of minimum horizontal stress (Shmin) from minifrac tests and observations of compressive failures from acoustic image log provided strong constraints on the SHmax magnitude in the studied Ordovician tight reservoir interval in the absence of core-measured rock strength.