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    Assessment of borehole breakouts from acoustic image log and its geomechanical implications - A case study from Triassic-Ordovician interval of Berkaoui field, southeastern Algeria
    (Society of Exploration Geophysicists, 2024) Baouche, Rafik; Sen, Souvik
    In this study, we interpret a cumulative 600 m acoustic image log across the Triassic to Cambro-Ordovician interval in the Berkaoui oil field, Algeria. We interpret 40 distinct breakout zones that have a combined length of 210 m. These breakouts are aligned in the north-northeast-south-southwest direction, indicating a mean maximum horizontal stress (SHmax) azimuth of 110°N. The observed breakouts are ranked as "A-Quality"following the World Stress Map ranking guidelines. The angular width of each breakout has been inferred from the image log analysis and the same has been used to infer the SHmax gradient by stress polygon approach following the frictional faulting mechanism. The stress polygon across all the breakout intervals provides a practical Shmax range between 24.7 MPa/km and 31.1 MPa/km, with an average gradient of approximately 27 MPa/km. Considering the Shmin range across the studied intervals, we infer a SHmax/Shmin ratio dominantly between 1.40 and 1.65, which is a much narrower and better-constrained range when compared with the previously published ranges from nearby fields with the same stratigraphy. The relative magnitudes of the in situ stresses indicate a strike-slip faulting regime in the Berkaoui Field. This study presents the utility of image log analysis and the integration of breakout interpretation to obtain a more robust geomechanical model with reduced SHmax uncertainty.
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    Constraining maximum horizontal stress using wellbore breakouts A case study from the Ordovician tight reservoir of the northeastern Oued Mya Basin, Algeria
    (Society of Exploration Geophysicists, 2024) Baouche, Rafik; Sen, Souvik; Ganguli, Shib Sankar; Benmamar, Salim; Kumar, Prakash
    In this study, we interpret the maximum horizontal stress (SHmax) azimuth from the breakout positions of the wellbore and attempt to constrain the SHmax gradient based on the interpreted breakout width. A cumulative of 110 m of breakouts are deciphered within the Ordovician Hamra Quartzite interval of the Oued Mya Basin from a 138 m acoustic image log. These breakouts are ranked as A-Quality following the World Stress Map ranking guidelines. We infer a mean SHmax orientation of N28 E ± 8. Following the frictional faulting mechanism and stress polygon approach, measurement of the minimum horizontal stress (Shmin) from minifrac tests and observations of the compressive failures from the acoustic image log provide strong constraints on the SHmax magnitude in the reservoir interval in the absence of core-measured rock strength. Interpreted breakout widths exhibit a range between 32.6 and 90.81, which indicates a SHmax range of 24.4-34.7 MPa/km. The average breakout width of 62.58 translates to a narrower SHmax gradient range, varying between 27.2 and 31.2 MPa/km. The relative magnitudes of the principal stresses indicate a strong strike-slip tectonic stress state. Considering all the uncertainties, we infer a SHmax/Shmin ratio of 1.41-1.81 within the Ordovician interval.