Building 3D geological model using non-uniform gridding for Mishrif reservoir in Garraf oilfield

Abstract

Mishrif formation is the main carbonate reservoir in southern Iraq, which is extremely heterogeneous and require accurate geological description for optimal oil field development. This research is associated with developing a representative 3D static model that conserves geological elements and relieves the uncertainty of reservoir properties and volumetric estimates. The interpreted log data and core reports were selected to capture all structural, stratigraphical and petrophysical properties. The reservoir is discretized with irregular cells using the tartan grid, concentrating their accuracy in important areas. A sequential Gaussian simulation algorithm distributed the petrophysical properties for all reservoir units. The structural model showed that Mishrif reservoir in Garraf oil field has a domal structure with two main producing reservoirs (M1.2 and L1.2). The petrophysical model results present that unit L1.2 has high-quality properties with average porosity of 0.24 and water saturation of 0.17 and less than in unit M1.2, where the average water saturation and porosity are 0.47 and 0.185, respectively. The estimated oil in place with the volumetric method was 901 Million standard cubic meters, most of which accumulated in unit L1.2. This study was applied to reappraise the reserves of Mishrif reservoir in Garraf oil field using irregular gridding.