Publications Internationales

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Author: search.filters.author.Baouche, RafikSubject: search.filters.subject.Algeria

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    Triassic-Early Jurassic evaporites of the Saharan Platform, Algeria: Astronomical and geodynamic constraints on stratigraphy and sedimentation
    (Elsevier, 2023) Turner, Peter; Baouche, Rafik; Sabaou, Nordine
    The sequence stratigraphy of the Late Triassic - Early Jurassic evaporites of the Berkine Basin is described. Disconformities occur between all the major evaporitic units but lack of biostratigraphy (or other) chronostratigraphic control precludes their precise dating. The S4 and S3 Halites are predominantly non-marine halites deposited in low-lying salinas with a barrier to the north. The top of the S4 depositional sequence is marked by the D2, usually regarded as the Tr-J boundary in the Berkine Basin. Both the S3 and S4 salt deposits thin rapidly to the south-east and are thicker in the basin centre coincident with a subcrop of Carnian? aged volcanics. A combination of thermal cooling, rifting and reactivation of N–S lineaments parallel to the Hassi Messaoud-El Biod Arch controlled the (∼1500 m thick) depocenter. Time series analysis shows that astronomical forcing played a key role in the deposition of the S3 and S4 bedded halites. The prevailing climate was monsoonal with major replenishment of the basin indicated by long eccentricity cycles (405 kyr). Sedimentation rates were estimated using eCOCO analysis with average rates of 15 cm/kyr. Well to well comparisons shows that in marginal areas thinner sedimentary sequences relate to slower accumulation rates and periods of non-deposition or deflation. The pattern is similar in the S4 and S3 halite, but the reduced mud content and amalgamation of halite beds suggests a more arid climate in S3 times. The S1+S2 unit marks the first widespread deposition of sulphate in the basin. The lowermost anhydrite beds of the S1 + S2 rest unconformably on the underlying S3 and overstep the basin margins in the south-east; the sequence is capped by the B Horizon a basin-wide carbonate shelf deposit about 25 m thick indicating increased marine influence. Above there is a rapid return to thinly bedded mudstone-halite dominated sedimentation (Lias Salifère) which is overlain by the Lias Anhydritique an alternating sequence of halite and anhydrite deposits. Astronomical parameters of the whole sequence indicate an average sedimentation rate of ∼10 cm/kyr in this marine-influenced section, slower than the halite units. Although the time series analysis cannot provide precision dating of the evaporitic sequences the results indicate that there are important breaks in the depositional record. The combined S4 and S3 halites account for 4.75 Ma and the rest of the Liassic 9.4 Ma. It seems clear that much of the depositional record is missing. These Saharan Platform basins bear much in common with other western Mediterranean evaporite basins. Many show the same overall pattern of sedimentation with increased sulphate deposition above the Tr-J boundary. In late Triassic time they formed a contiguous low-lying zone flanked by cratonic highlands. This zone spanned the Gondwana-Laurussia boundary immediately prior to its break-up and Greater Adria formed a barrier between these basins and the developing Neotethys to the east. The major changes seen in the Saharan Platform are mirrored by the break-up of Adria and the separation of Gondwana and Laurasia and the ultimate connection of the western Mediterranean and the central Atlantic.
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    Determining shear failure gradient and optimum drilling mud window in the ourhoud oil field, berkine basin, Algeria
    (2022) Baouche, Rafik; Souvik, Sen; Hadj Arab, Feriel
    Optimum drilling mud window provides a workable downhole mud pressure range to prevent formation fluid influx, borehole instabilities, and fluid loss into the formation while drilling, and this can be achieved by a comprehensive geomechanical modeling using well data. We have integrated the wireline logs, drilling data, and measured downhole data to assess the vertical stress, pore pressure, minimum horizontal stress, and shear failure (SF) gradient of the 3400 m thick Mesozoic and Paleozoic succession in the Ourhoud field, Berkine Basin. We interpreted the hydrocarbon pressure gradient in the Triassic Argilo-Greseux Inferieur reservoir as 0.32 psi/ft and found the overburden shales to be hydrostatically pressured (0.46 psi/ft). Poisson’s ratio-based minimum horizontal stress has a 0.73–0.80 psi/ft gradient, whereas frictional faulting theory provided a lower limit of 0.66 psi/ft. We observed massive wash outs in the caliper logs against the Cretaceous shales, which is more prone to compressive failures. To address this wellbore failure, we modeled SF gradient by Mohr-Coulomb rock failure criteria and compared the results with the mud pressure used in drilling. We inferred that at least 10.5 ppg drilling mud weight is required to prevent such wellbore instabilities in the Mesozoic shales, whereas the minimum allowable mud weight for the Carboniferous shale is 10 ppg. Based on the interpreted pressure gradients, we have recommended an optimum downhole drilling window for the Ourhoud field, which will be helpful to deliver stable wellbores in future drilling campaign
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    The use of the modular dynamic tool in petrophysical parameters evaluation : application to the Bir-Berkine reservoirs - Algeria
    (2008) Baouche, Rafik; Nedjari, A.
    The technological development and the complexity of the reservoirs unceasingly encourage us to improve our working methods, of acquisition processing and interpretation of well logs, but the information provided by the well logs related to the localisation of hydrocarbons bearing zones is not perfect. The Modular Dynamic formation Tester (MDT) is a new generation of tools designed for the more pointed tests of formation. By using its various configurations and options it offers, unquestionable opportunity to obtain, starting from the pressure taps, a varied range of invaluable information for the management of the reservoirs. The virgin reservoirs service MDT is used:To determine the levels of the contacts of fluids (WOC and GOC): to determine the densities of the fluids; to characterize the reservoir heterogeneity; to decide the completion mode; to optimize the mud density to be used. In the development of reserves: to establish a pressure profile; to estimate the vertical and horizontal permeabilities; to detect the robbers zones; to determine the communications between the wells; The principal goal of this work is by combining the results of petrophysic measurements and pressure. To achieve this goal the study is articulated on four essential points:• The evaluation of the petrophysical parameters of the Bir-Berkine reservoirs; • Interpretation of pressure measurements; • Well to well correlation; • Result synthesis
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    A sedimentological approach to refining reservoir architecture using the well log data and core analysis in the saharan platform of algeria
    (2009) Baouche, Rafik; Nedjari, A.; Eladj, S.
    Improved reservoir characterisation in the mature oil applied to Gourara Field of Sahara in Algeria, aimed at maximising both in-field and near-field hydrocarbon potential, requires a clearer understanding of sub-seismic stratigraphy and facies distributions. In this context, we present a regional, high-resolution sequence stratigraphic framework for the Oued Namouss Field based on extensive sedimentological re-interpretation of core and wireline log data, combined with core analysis and published literature. This framework is used to place individual reservoirs in an appropriate regional context, thus resulting in the identification of subtle sedimentological and tectono-stratigraphic features of reservoir architecture that have been previously overlooked. We emphasise the following insights gained from our regional, high-resolution sequence stratigraphic synthesis: (1) improved definition of temporal and spatial trends in deposition both within and between individual reservoirs, (2) development of regionally consistent, predictive sedimentological models for two enigmatic reservoir intervals (the Formations I and II), and (3) recognition of subtle local tectono-stratigraphic controls on reservoir architecture, and their links to the regional structural evolution of the Province. We discuss the potential applications of these insights to the identification of additional exploration potential and to improved ultimate recovery.In this research a procedure was developed to assess and quantify uncertainties in hydrocarbon estimates related to depositional facies, petrophysical data and gross reservoir volumes. This procedure was applied to the Gourara Field, which is a mature gas field in the Oued Namous Basin, Algeria. The aim was to investigate the reasons for an unexpectedly high hydrocarbon recovery factor
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    Petrophysical analysis in reservoir characterization : application in the triassic hamra gas field, Algeria
    (2007) Baouche, Rafik; Nedjari, A.; Said, E.
    Petrophysical evaluation of the Upper and Lower shaly gas sand reservoirs of the Sahara field, using conventional well log interpretation techniques and relating the results to core data, shows that the Upper reservoir is of very good quality and apparently better than the Lower reservoir. Evaluation of the petrophysical parameters from the wells in the field show porosities ranging from 12 to 20% and permeabilities of about 500 mD, which are similar to regional values of 12 to 20% porosity and 1000 mD permeability. A crossplot-based lithological study shows that the matrix is dominantly quartz, with calcitic and dolomitic cements, a high percentage of montmorillonite clays, and a smaller percentage of illite and micas. A study of lateral variations of petrophysical parameters shows that porosities increase from NE to SW, similar to the saturations. This study shows the role of wireline petrophysical analysis as a tool in reservoir characterization of shaly sands in the Sahara field. This paper examines the use of log analysis and mean petrophysical reservoir parameters as a tool in successfully establishing reservoir architecture and fluid-flow trends. Data from Gamma Ray, Neutron, Density, Sonic and Resistivity logs was utilized for petrophysical analysis to correlate layers in this reservoir characterization study. Petrophysical evaluation of the Shaly Sand gas reservoir (TAGS) of the Rhourde Hamra field, using conventional well log interpretation techniques and relating the results to core data, shows that the reservoir is of very good quality