Pushing the Limits of Depletion Optimization Towards a Hybrid Field Development Plan in a Complex Giant Offshore Carbonatea Reservoir-Comprehensive Scoping of Technical and Economic Viability

摘要

The subject reservoir is a geologically complex Lower Cretaceous carbonate system, which is on water flood recovery scheme. Due to extreme diagenesis and associated geologic heterogeneity (which include faults, fractures, burrows and algal floatstone), water breakthrough occurred early and oil recovery is low due to water channeling and by-pass of huge volumes of un-swept hydrocarbon. The low recovery performance is compounded by the relative thinness of the reservoir as well as unfavorable mobility characteristics due to disparity in oil and injected water viscosity. The unique interplay of geology and fluid properties confer special displacement characteristics to the reservoir, which despite extensive literature review for similar architectures in a wide range of geologic settings yielded limited results. Despite previous recovery enhancement efforts through workovers, well spacing optimization, and horizontalization, water production has steadily increased. As a key growth contributor in a massive Brownfield re-development project, the reservoir is currently undergoing intensive drill campaign been executed from artificial islands. The strategy underpinning the redevelopment effort involves holistic evaluation, optimization and selective application of innovative well completion technologies, including MRC (Maximum Reservoir Contact), EMRC (Extended Maximum Reservoir Contact), Trilateral, Fishbone, ICV (Inflow Control Valves) and Infill for low-drawdown depletion concept. For Fishbone, the considered design parameters include branch angle, length and numbers. Branch displacement from the mainbore was a key design assessment for Trilateral in view of the potential for injection support buffering by the flank branches. For the Infill, optimizations include spacing and timing. A new ICV logic was implemented on a full field basis to assess incremental opportunity capture through flow restrictions in high water flux intervals. Layer placement sensitivities assessed which zone placement configuration maximizes targeted sweep of bypassed oil. The life cycle production forecast of various completion scenarios per drainage pattern were compared among themselves utilizing technical and economic criteria for identification of the completion that generates maximum value leading to the generation of a hybrid full field, life cycle optimized development plan consisting of MRC/EMRC, Trilaterals, ICVs and infill wells which are currently been executed.