Usan Field: Maximizing Production from New Drillwells in a Hydraulically Constrained Deepwater Subsea System Using IPM suite

Abstract

Abstract Usan, a deepwater field located offshore of Nigeria, commenced production in February 2012 with development drilling to be completed in 2016. The field has 2 subsea flowline loops with 4 risers giving the flexibility to flow wells through two different risers. Due to the constrained flowline capacity, optimization of well routing and drillwell sequencing became critical to sustain the remaining drillwell campaign while maximizing base production and incremental uplift. The adopted approach by the Production and Reservoir Engineering teams was to utilize the Integrated Production Modelling (IPM) software suite (PROSPER, GAP & RESOLVE) to ensure optimal well mix and flow stability. A systematic approach of continuously testing various routing scenarios of wells within the different production loops was applied to minimize production back out loss due to system hydraulics during the streaming of new drillwells. Different ramp-up scenarios were also tested for the new wells to minimize back-out on base wells. Due to variations in fluid properties, reservoir pressures, depletion strategies and loopline distance, the system needs to be re-evaluated frequently. With over 50 routing sensitivities assessed at each evaluation, identifying and implementing the optimal routing/configuration became critical. Production optimization using the IPM model has led to higher FPSO incremental rates from new drillwells due to optimized well routing within the production risers. This has also helped to sustain the ongoing drilling campaign in the Usan field and improved the economics of the overall project. This paper describes how IPM software was used to maximize incremental production from new drillwells.