Reservoir Characterisation And Modelling In A Fractured Upper Cambrian Quartzite Reservoir, Algeria
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This presentation describes reservoir characterisation carried out on an Upper Cambrian fractured quartzite reservoir at Rhourde El Baguel field in eastern Algeria. The field, which started production in 1963, was taken over by Sonarco in 1996 who initiated infill drilling and a miscible gas enhanced oil recovery project. Subsequently the field has come under the ownership of BP / Sonarco. The highly heterogeneous geology and flow properties of the reservoir host rock were expected to have a significant impact on the performance and success of the miscible gas flood. A robust description of the fracture system was essential to reduce uncertainties associated with flood efficiency and recovery. In addition, primary depletion of the reservoir prior to 1996 had resulted in a significant drop in pressure (around 4000 psi), and therefore coupled geomechanical effects were expected to accompany re-pressurisation. These might influence reservoir performance and operational activities. Over 80 wells have been drilled at ReB and these provided the major dataset for reservoir characterisation. Seismic data was available but is unfortunately of poor quality. Outcrop analogue data was also available and proved of significant benefit for upscaling from the well observations. From these sources, detailed fracture characterisation was used to build local-scale fracture models of key areas in the field, which were used to underpin reservoir simulations. In parallel, detailed observations of reservoir stress were made and used to help evaluate coupled geomechanical effects. The work has shown that reservoir characterisation utilising the techniques described here can significantly reduce development risk and can be applied in similar contexts.
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