Abstract
Many fields in the Niger Delta are made up of stacked reservoirs. Conventional completion and production are by bottoms-up approach. Multizone completion using one string as a key element of Brown Field Excellence is novel or at best evolving in Nigeria. It ensures many reservoir intervals are completed and comingled during production and has many benefits. Major challenges are delivery schedule of equipment, additional regulatory approvals and cross flow that could impact both rate and ultimate recovery. Proactive engagements for co-creating the solution at design phase is a panacea for successful multizone completion workover. In this paper, a muti-tank material balance reservoir model was built and used to predict performance and cross flow phenomenon in eight comingled stacked reservoirs. Most importantly, the model shows that in this novel approach of WO recompletion it is possible to achieve an instantaneous potential of 11.5 Kbopd with 8 zones comingled even in the presence of cross flow from an old well that made a maximum of 3.0 Kbopd from conventional completion. By closing the cross flow big heater reservoir from the onset behind sleeve till cross flow ceases following pressure equilibration, it is even possible to achieve initial instantaneous potential of 12.0 Kbopd. It is recommended to use the model to close behind sleeve, interval with negative flow rate (cross flow) during production of the multi zone completed well. The modelling approach in this paper is recommended for application in other Brown Field Excellence multi zone completions in any multizone workover portfolio. The model could also argument hydrocarbon accounting techniques of routine finger printing and production logging since it predicts contributions of all fluids from each zone viz oil, gas, and water rates as a function of time.