An Effective Small Scale Pressure Maintenance Scheme - Conception to Implementation - A Case Study

Abstract

Reservoir Depletion is addressed in many ways across the globe with water injection being the most common method. A typical full field water injection scheme takes years for implementation, with surface players like injection facility construction dominating the project cycle and delays are not uncommon. The resulting loss in deferred production and recovery along with continuous amendments to production profiles of the field can be minimized by resorting to DumpFlooding as an easy and quick alternate.ЉAЉ field is a satellite field of Kuwait. Bulk of production is from the thin estuarine channel sand of average thickness of 13ft within Zubair Formation. This channel system is laterally continuous as interpreted from the Isopach map and has a fairly uniform pressure throughout the field. With no aquifer support, a decrease in pressure from the initial levels of 2500 psi by around 1000 psi was observed. The production performance also deteriorated since the operational teams had difficulty keeping the ESPs on operation continuously. The size and location of the field could not economically justify a conventional water injection project. As the reservoir pressure came perilously close to the bubble point, a partial pressure maintenance scheme was conceptualized, with DumpFlooding as injection mechanism.A systematic plan to address all the uncertainties that could have an impact on the success of the project was listed and addressed. The injection volumes and injection patterns were evaluated and firmed up by a simulation study. Various source water reservoirs were identified and water compatibility analysis was carried out to confirm the suitable injection water. Multiple single well pilots with completions from different source water reservoirs were tested. The productivity & injectivity indices of the different sources and the sink were ascertained. When the full field implementation was carried out, the team was able to take further steps with considerable confidence, having taken important lessons from each stage.The concept proved to be successful with real benefits seen on the ground. The layer saw a gradual rise in reservoir pressure monitored by an intensive surveillance programme. A rise in pump intake pressure of ESPs ranging between 150 to 200 psi within a span of 1 year was noticed. The field started experiencing trouble free ESP operation. New horizontal producers drilled as a part of the scheme resulted in significant oil gain. A 25% increase in overall layer production was observed. The paper discusses the key milestones from conception to implementation with emphasis on the role played by each stage in the grand scheme of things. A case is thus made for considering DumpFlooding as a necessary intermediary in any upcoming water injection project.