The North Kuwait asset has several stacked producing reservoirs, further subdivided into multiple sub-layers, each sub-layer with substantial production potential. Over 75% of these sub-layers are depletion drive reservoirs requiring water injection for pressure support. Many existing/planned Injectors penetrated over- and under-lying layers that has good production potential. Similarly, many Producers penetrated adjacent reservoirs/layers that required injection support. With limited surface real estate available to accommodate the increasing demand for appropriately located Injectors and Producers, conventional single-purpose wellbores have become an unaffordable luxury.
An innovative concept was developed in-house by using a single wellbore for an unconventional dual purpose, namely, Simultaneous Injection and Production (SIP). Owing to the significant differences in fluid rates and temperatures, absolute and relative tubular movement play a significant role in completion integrity and longevity. Collaboration with one of KOC’s major Electrical Submersible Pump (ESP) service partners yielded a unique dual concentric design that facilitates ease in completion deployment and equal ease in retrieval when necessary. Two (2) scenarios were considered in the dual concentric Completion design, namely Inject above, produce below (Scenario – A), and Inject below, produce above (Scenario – B). Tubing stress/movement software were used to simulate and design tubular specifications that would maintain optimum completion integrity in either of three (3) Operating Conditions: Inject only, Produce only, and Simultaneous Injection and Artificial Lift Production.
Due to the complexity and uniqueness of the SIP configuration, completing the Well on Paper (CWOP) sessions proved to be a very effective tool in the planning process of this completion.
The ESP Service Partner performed a System Integration Test (SIT) in a test well to verify equipment functionality and optimize the assembly procedure. Following the successful (SIT), the first installation was completed in early 2017. The systems installed to date were originally Producers that were ideally located for injection in an adjacent reservoir. The new Injection layer was stimulated initially, to assure maximum injectivity and longevity. The outer 5½" ESP Production string was run and landed first, followed by the inner 3½" string. The ESP’s were operated initially while the surface injection flow lines were fabricated and connected. Injection was then commissioned and monitored for inter-string communication. Initially, zero communication was observed with over 14,000 bwpd consistently injected over certain injection periods while maintaining original production rates. Evidence of possible leakage and inter-string communication was observed after seven (7) – eight (8) months of continuous injection. Investigations and analysis of integrity-longevity-failure to conclude root cause(s) and remedial solutions are still ongoing, where an upgraded design and improved operating procedures, shall be eventually formulated.
Previously only conventional dual parallel strings were deployed for Injection and Natural flow production. Now this unique and innovative design of Dual Concentric strings, first of its kind in the world, has raised the bar in the application of Simultaneous Injection and Production. This Workover-deployed completion eliminates the burdensome development costs of drilling new Injectors and Producers in this deep, multi-layered, stacked, depletion-drive reservoir environment. KOC has initiated a key technology that has significant global application, especially in offshore environments.
