Paul M. Button & Eugene Wadleigh, Marathon Oil Co.
An innovative approach has been used to model flow through discrete fracture networks in a massive carbonate reservoir in order to understand and predict performance of vertical and horizontal well completions. This approach focuses on completion effectiveness and the influences that fractures have in a three-phase gravity influenced flow system. The model is set up as a dual porosity, dual permeability simulation of a discrete fracture network of high permeability grid blocks capable of modeling three-phase flow. This model reveals the dominant factors controlling well life cycle performance demonstrated in the Yates Field Unit Natural fracture networks dominate flow throughout the reservoir with added economic significance to completion efficiency. Therefore 3D discrete fracture network (DFN) models based on connected-fracture orientation from FMI logs and flow surveys have been used as a basis for constructing the 3-phase simulation grid. The differences in mobility between the three phases result in abnormally shaped gas-oil and water-oil contacts as drawdown is applied. As the fracture oil column depletes, oil mobility reduces with the decrease in effective fracture connection to the outlying oil column. This loss of oil mobility through phase dis-connection in flow conduits has not been the focus of prior studies. The simulator has successfully generated production profiles similar to those observed in field performance data. This wellbore simulation has been used to develop a strategy for optimal completion performance and placement.