A Modeling Approach for Optimizing Waterflood Performance, Wara Reservoir of the Greater Burgan Field, Kuwait

Abstract

The Greater Burgan Field is located in southeastern Kuwait, covers a surface area of about 800 square kilometers and is ranked as the largest clastic oil field in the world. The field comprises six main reservoir units, namely Wara Sand, Mauddud Limestone, Burgan Sand Upper, Burgan Sand Middle, Burgan Sand Lower and Burgan Fourth Sand, stacking on top of each other. The Wara Shale acts as a barrier separating Wara from the massive sands of the underlaying Burgan formation. However, extensive faulting does allow communication between the Wara and the Burgan Sands. Production was initiated from the Greater Burgan Field in early 1946. As the field has matured over time, the reservoir pressure has declined in certain areas, with associated reduced productivity. The reduction of wells’ productivity, combined with the increasing water production, has necessitated improved oil recovery (IOR) initiative in order to support the Kuwait Oil Company (KOC) 2030 strategy, sustaining a corporate target oil rate and ensuring high recovery from Burgan reservoirs. This paper describes the modeling effort in designing the Wara Pressure Maintenance Project (WPMP). The WPMP is the first major full-scale waterflood project implemented in the Greater Burgan field. The management decision was based on the fact that Wara has experienced significant pressure decline after 68 years of primary production. Weak edge water drive, combined with poor reservoir connectivity, has resulted in deteriorating productivity along with creating secondary gas caps in some areas. In 2005, design for a pressure maintenance project (PMP) 2 via a peripheral waterflood was initiated to arrest pressure decline and improve oil recovery. Indeed, it became a major component of the Greater Burgan Field Development Plan (FDP) and is now entering the operation stage after 10 years of planning and facility construction. The Greater Burgan FDP is supported by a massive sub-surface modeling project. It started in 2009 with the sequence stratigraphy model (Phase-1) followed by geological model (Phase-2) 6 and dynamic model (Phase-3) 9. All modeling projects were conducted by reputable consulting firms with significant KOC hands-on participation and project management. The three modeling phases were concluded in 2013 and a simulation prediction model has been developed as a premium FDP reservoir management tool. In this paper, we focused on the modeling of the WPMP which was built meticulously and comprehensively to produce an optimal development and operation strategy. This includes project phasing, waterflood pattern design, producer/injector locations, drilling sequence, polygon setup for voidage replacement ratio (VRR) control, and constraints for good reservoir management practice. Sensitivity on constrained and unconstrained cases was included to evaluate future facility requirement. All in all, a robust simulation model to optimize Wara waterflood performance and ultimate recovery.