Three Observation wells have been successfully put back on production with average 200 Barrel Oil Per Day. Generally, the Observation wells were never evaluated anymore since they have more than 99 % or even 100 % water cut. Production of a high water cut well is so difficult to be optimized that it is assumed that the well has no oil anymore and will be abandoned. Besides that, since water has higher specific gravity and sweep efficiency and lower viscosity than oil, usually the well is assumed to have water coning problem. To maintain oil production in gentle slope, a Modern Reservoir Management Process has been implemented by building a synergy team among the Earth Scientists, Reservoir engineers and Production Engineers, named Subsurface Team. The standard data needed are cross-section, structure maps, production history data, Cased Hole Logs (CBL. PLT, PSGT/CO), and Formation-Evaluation data by using Mincom. Cross-section generation, the important data, is based on sequence of stratigraphy where wireline logs have to be conformed with core data analysis. A sequence of stratigraphy approach is used to determine sand continuity where entirely Minas oil field is dominated by fine to medium sandstone that can be divided into 6 hydrocarbon bearing reservoirs which are Al, AZ BI, B2, D and S. It is important to know flow conectivity either vertically or horizontally because there is potential of fluid flow barrier on the inter-face boundary. By knowing sequence of stratigraphy could be determine bypass oil. The performance history of surrounding wells are also used as references as long as they have the same rock properties as the subject well.
Authors : Gantok Subiyantoro & Kunto Wibisono