Identification of Major Factors and Adjustment Strategies for Water Injection Development in a Complex and Thick Carbonate Reservoirs in Middle East

Serious water channeling, wells shut-in due to rapid water cut rise, and challenge in oil production ramp-up were always perplexing problem in a typical super thick (generally effective thickness exceeding 200 m) porous carbonate reservoir in Middle East, which can be attributed to strong heterogeneity, difficult characterization of Super K layers and flow barriers and unclear impact on waterflood performance and complex oil-water migration, difficult identification of main controlling indicators in commingle development mode. Therefore, it is almost impossible to carry out classified strategy on well-level and reserve-level to help oil production ramp-up. In view of strong heterogeneity of the targeted reservoir and rich dynamic surveillance data, a data splitting method for vertical well commingle development based on Capacitance Resistance Model (CRM) is developed, then a workflow to determine major factors for water flooding is proposed and according water injection adjustment strategy is studied. Firstly, integrating geological and reservoir data, injection production characteristics of Super K layers and flow barriers were identified and their effect on water flooding performance was evaluated, and then commingled data was split based on Production/Injection Logging Testing (PLT/ILT) and dynamic permeability correction (no PLT/ILT available), to determine production and water cut by layers and wells; Secondly, injection production relationship by layers and wells was quantified based on an improved CRM,which calculate dynamic connectivity coefficient by layers and effective oil increment; Thirdly, main controlling factors and zones for waterflood aerially and zonally are determined, integrating with split production, water cut, dynamic connectivity coefficient and oil increment by layers and wells; Finally, water injection adjustment strategies for existing vertical well in commingle development mode was formulated considering different types of main control zones. Based on the application of the proposed method and workflow in a typical thick porous carbonate reservoir in Middle East, the calculated production by layers and wells is consistent with that of numerical simulation, but simpler and faster. 4 major factors under current well pattern can be effectively identified, i.e. fault zones, tidal channels, granular beaches, and edge water, and their influence areas can be delineated, An adjustment strategy based on these 4 types of main control areas is proposed: moderate and gentle water injection recommended for fault zones and edge water zones to stabilize oil and control water cut rising, water shut-off workover implemented for granular beach areas, and vertical wells recompleted in top layer only for tidal channel area, which can further improve oil recovery by 3–5% and support future development deployment, which provides significant reference for water flooding management of similar carbonate reservoirs.