Optimal Infill Drilling Using Simulation and Cross-Functional Integration- Ubit Field Example

The Ubit Field, located southeast of the Niger Delta, is a Nigerian National Petroleum Corporation (NNPC)/Mobil Producing Nigeria (MPN) Joint Venture (JV) asset that has been on production for more than 40 years (September 1970). Ubit has approximately 2.4GBO OOIP, with production peaking at ~137,000 BOPD in 1997, and is currently at ~85,000 BOPD. With much of the reserves yet to be produced, it is important that an optimized field development plan be implemented to maximize recovery. Guided by reservoir simulation models, a revised Ubit Field re-development plan was approved in December 2009. Infill development has proceeded as designed, and the first infill drilling program is underway. Integration of results from reprocessed seismic, geologic interpretation, core, log and reservoir simulation studies, coupled with state of the art technology in well completions, were critical in developing an optimized depletion plan. Reservoir simulation results consistently indicate higher reserves capture with increased well density from infill drilling that targets unswept locations around and down-dip of abandoned completions. Results from the integrated studies suggest varying the optimum well spacing requirements for the different sections of the reservoir. The recovery factor in the lower quality reservoir section (Disturbed Biafra) could be vastly improved by increasing well density. The multidisciplinary study for field development indicates that approximately 100 additional wells should be drilled to tap unswept resource in the field. This aggressive approach will maximize ultimate recovery, but requires closer well spacing than minimum regulatory specification . The technical basis for this strategy, primarily reservoir simulation models anchored in measured hard-data, is the core focus of this paper.