Reservoir Evaluation Model of the Khasib Formation in Halfaya Oil Field, Mesan Governorate, Southern Iraq.

Abstract

Evaluating the reservoir characteristics of a formation or geological unit constitutes an essential element and an effective tool in leading the successful exploration project currently prevailing. The Khasib Formation, which belongs to the secondary depositional cycle (Turonian - Lower Campanian) in the study area within Mesan governorate southern Iraq, was chosen as a study site, as the Khasib is one of the main reservoirs within the Mesan oil fields. Seven wells were selected distributed over the field area, which structurally, is represented by two domes oriented from NW to SE, in addition to a thin dome with a length of 38000 m. and a width of 12000 m. The corrected well logs were used as input by creating an Excel sheet and then processing that data through the Petrel Software to prepare maps, sections and Three dimensional diagrams. The Cross-plot diagrams showed that the limestone (calcite) is a main lithology of Khasib with some dolomite. 3-dimensional petrophysical models were prepared, through which identified three reservoir units: (Khasib-A, Khasib-B and Khasib-C). The porosity model shows that there is a good percentage of porosity within the Khasib-A unit, with a low percentage in unit-B. As for unit-C, it was characterized by the best porosity percentages. The water saturation model showed a high percentage at Khasib-A unit, reaching 80%, and it increased at unit-B, reaching 90%, while unit-C was characterized by the lowest percentage of water saturation. The volume of shale model indicates low to moderate rates in the Khasib-A unit, and a slight increase in unit-B, while unit-C showed a low rate of shale volume within the three units with very low values in most of the study wells, which confirms the superior quality of this reservoir unit, which can be considered the main productive reservoir unit of the Khasib Formation in the Halfaya oil field.