Injector Well Performance Optimization

Abstract

AbstractThis paper presents an integrated multi-disciplinary approach to optimize the value of water, that is, barrels of water injected per barrel of oil produced. Value of water (VoW) is optimized through focusing on the following critical components of a successful injector: Optimum drilling and completion programAbility to inject above fracture pressureInjection system availability with high water qualitySurveillance and analysis-driven ramp-ups to target injection ratesDrilling program optimization includes well trajectory alignment with maximum horizontal stress, selection of acid-soluble stress cage materials when used, and considerations involving proper perforating gun selection. Completion design optimization includes vertical and/or near vertical entry to the formation, an efficient completion type selection based on the rock strength/competency, proper breakdown of the formation along with a pre-injection acid treatment.The topsides facility requirements for injecting above fracture pressure is ensured with full field thermal geomechanical simulations coupled with injection network models to capture the changes in fracturing conditions with depletion and cooling. These simulations also incorporate injectivity decline models required to account for injection water quality variations over time. Topside's injection water specifications are maintained through filtration and chemical treatments with daily measurements of sulphate, oxygen, chlorine levels for souring and scaling prevention.Surveillance and analysis-driven ramps to target injection rates are achieved by integrating multiple methods for efficient diagnostics along with signposts; advanced Hall plots for real-time continuous monitoring, numeric/analytic pressure transient analysis for reservoir characterization, skin tracking, material balance methods for investigating aquifer support, and history-matched integrated thermal/geomechanical simulation models to gain insights into dynamic fracture behavior for improved sweep.Case studies from several deep offshore injectors show how the integrated multi-disciplinary approach was successfully used to drill, complete, and operate injectors. Initial negative skins point to the successful optimization of drilling and completion programs. Sustained injectivities for more than 5 years demonstrate the benefits of surveillance and analysis-driven, consistent, and repeatable ramps with rest periods during unplanned shutdowns. Field data along with numeric/analytic reservoir studies suggest good support of producers and low VoW numbers.This work combines the best practices for a successful injector in the areas of reservoir engineering, geomechanics, drilling, completions, production, and operations. Also, an extensive holistic injector well performance analysis approach is outlined integrating thermal/geomechanical/ geochemical simulations, numeric/analytic pressure transient analysis (PTA), advanced Hall plots and injection network/wellbore models.