Subsurface Waterflood Management Improvement: The Art of Reservoir Connectivity Characterization

Abstract Developing subsurface waterflood management strategy at mature field and complex stratigraphic trough advance and integrated analysis of various subsurface discipline is very critical to characterize reservoir connectivity to improved oil recovery. This paper focus on technical analysis of defining the vertical and lateral connectivity practically applied for injector-producer well alignment. Detailed study has been done as efficient approach to evaluate waterflood connectivity performance in complex compartmentalized reservoir. Advance and integration of analysis of all subsurface discipline aspect as a foundation of static and dynamic studies trough stratigraphy interpretation, seismic wave propagation, log shape clustering analysis, pair analysis of linked injector-producer, spinner surveillance analysis, and CRM (capacitance resistance modelling). Combine all those analyses to fill the gap of each method and validate with pressure analysis and production data is key to reduce uncertainty. Integration of these analysis provides better understanding of injection–production relationship, water cycling well, water breakthrough impacts and unoptimized production reservoir. The recommendation was used to lead further injection–production alignment strategy. Waterflood management has successfully implemented and is able to put more injections at the right place, right amount and right time. Workovers and well intervention program are executed as plan in both injector and producer wells and successfully delivered additional oil gain impact to 50% of total production. A significant additional reserve has been achieved through this new workflow implementation. The other benefit from this effort was creating additional fluid space at the current constrained surface facility that allow to execute delayed workovers. A better understanding reservoir connectivity has improved workover success rate from 67% to 95%. In overall, this initiative has successfully managed Alpha field annualized decline from 41% to 28%. This methodology and workflow can be applied to other waterflood fields that have similar conditions. Integrating subsurface assessment, surveillance, and engineering data has proven to improve the performance and recovery of the Alpha field. The extensive application of reservoir connectivity appears to be an important tool to economically extend the life of this mature field, achieve high recovery, and maintain production decline. Diligent and creative integrated subsurface and engineering analysis can provide an excellent optimization strategy for mature waterflood fields. The project team was able to exploit the upside potential to increase the oil field performance through the implementation of this integrated methodology.