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Author: search.filters.author.Ganguli, Shib SankarSubject: search.filters.subject.Berkine basin

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    Petrophysical, geomechanical and depositional environment characterization of the Triassic TAGI reservoir from the Hassi Berkine South field, Berkine Basin, Southeastern Algeria
    (Elsevier, 2021) Baouche, Rafik; Sen, Souvik; Ganguli, Shib Sankar; Hadj Arab, Feriel
    An integrated knowledge of the sedimentological data, petrophysical and geomechanical characteristics significantly enhances the understanding of the reservoir properties, leading to a reliable subsurface modeling. This work presents a comprehensive reservoir assessment of the prolific Triassic Argilo-Gréseux Inférieur (TAGI) sandstones of the Hassi Berkine South (HBNS) field, Southeastern Algeria. The Lower Triassic producer appears to be laid down on the Late Devonian erosional surface (Hercynian unconformity) in a fluvial depositional system. Based on the sedimentary structures, a fluvial depositional environment is deciphered from cores. Lateral and vertical disposition of the channel and floodplain deposits from regional well log correlation infers a shift of depositional regime from braided in the SW to meandering in the NE direction. Two distinct reservoir rock types (RRT) are interpreted from core-based petrophysical assessment. RRT1 is composed of macro-megaporous medium to very coarse grained amalgamated channel sandstones and yields the best reservoir attributes, while the mesoporous fine grained RRT2 translates to impervious to poor reservoir quality. RRT1 channel sands are found to be laterally continuous, while the fine grained crevasse splay sands corresponding to RRT2 are laterally discontinuous, thus making them difficult to correlate field wide. Rock-mechanical property-based in-situ stress estimates suggested a normal to strike-slip transitional (Sv ≥ SHMax > Shmin) stress state in the TAGI Formation. Direct measurements indicate that the TAGI reservoir had an initial pore pressure gradient of 11.08 MPa/km and is presently depleted by 2.1–2.5 MPa. A stable depletion stress path value of 0.57 is inferred considering a pore pressure-minimum horizontal stress coupling. At the present-day depletion rate, normal faulting is unlikely to have happened at the TAGI reservoir level and it can be depleted by another 25 MPa before inducing any production-induced reservoir instabilities
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    Integrated reservoir characterization of the Paleozoic and Mesozoic sandstones of the El Ouar field, Algeria
    (Elsevier, 2020) Baouche, Rafik; Souvik, Sen; Debiane, Kahina; Ganguli, Shib Sankar
    This study presents the interpretation of depositional environment and petrophysical properties of Mesozoic and Paleozoic reservoirs from the south-eastern Berkine Basin, Algeria by integrating core analyses and geophysical logs. Sedimentary structures and ichnofossils identified from 100 m of recovered cores have been interpreted to characterize the depositional settings of the studied reservoirs. During the mid-late Triassic, fluvial to marginal marine processes deposited the TAGS and TAGI reservoirs, while the Palaeozoic megasequences are characterized by shallow marine reservoirs (tidal bars and foreshore deposits) interbedded with thin marine shales. Porosity and water saturation have been estimated from geophysical logs and calibrated with core-based laboratory measurements. An empirical relationship between core porosity and permeability has been established for the El Ouar area and the same has been employed to generate a continuous and confident permeability profile against the target reservoir formations. Petrophysical characterization indicates a higher porosity and permeability in Triassic and Carboniferous sandstones than the Devonian F6 members. Triassic TAGS and TAGI sandstones possess the highest reservoir qualities in the El Ouar field. The Thorium and Potassium content available from spectral gamma-ray data have been utilized to identify the clay types associated with various sandstone reservoirs (Illite in Triassic sandstone, Kaolinite in Carboniferous units, mixed clay and Th bearing heavy mineral dominance in Devonian units). The study will be helpful for understanding of hydrocarbon resource potential and subsequent production planning in the study area.