Abstract

The Obaiyed gas/condensate field is located the Western Desert 50Km South of Marsa Matrouh. The Jurassic Lower Safa member (the reservoir bearing unit) consists of massive sandstones, which after deposition were subject to extensive deformation. A wide range of reservoir qualities is found in the field, with permeabilities ranging from tight (sub 0.1 mD) to high (up to 600 mD). Even after drilling 11exploration/appraisal and 30 development wells in the Obaiyed area, there are still significant subsurface uncertainties in the reservoir quality and extension, as shown by the 20% failure rate of the development wells. In order to improve our understanding of the Lower Safa reservoir, EREX Egypt was asked to make core descriptions for 15 wells in the Obaiyed field. They described 824m out of 1300 m total core length, to determine the depositional model of the Lower Safa. The conclusion of the study was that the main reservoir can be described as an estuarine deposit, with strong tidal influences in the earlier sequences, that evolved vertically into a wave-dominated deposit. The sedimentological study resulted in a simplified facies scheme that was used in Petrel to generate a 3D model for history matching. Unfortunately, it proved impossible to make a core-log correlation that could guarantee the successful production of new development wells. It was decided to take the reservoir quality uncertainty as a given and develop a completion strategy that would enable BAPETCO to produce the wells in any case. Therefore BAPETCO is planning a staged massive frac strategy in the coming years in parallel to the infill drilling campaign to maintain our production plateau and increase the ultimate recovery from the field.

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