Deviated wellbores are more common-place in the industry in recent years as Maximum Reservoir Contact (MRC) is the preferred strategy in wellbore construction. These high-angle, tortuous wellbores, however, have now limited the artificial lift options to Electric Submersible Pumping systems which are capable of sustained life cycles in high-watercut, low-pressure, and/or low-rate completions. Production logging and Coiled Tubing intervention in multi-layered completions and/or multi-compartment horizontal laterals equipped with Electrical Submersible Pumping systems has customarily been a major challenge, especially when the bypass fluid velocities are below the motor-cooling threshold for a conventional Y-tool configuration.An innovative design comprising of a shrouded Electric Submersible Pump with Y-tool combination is able to facilitate access to any completion that requires production logging and/or CT intervention. At relatively low fluid rates, the shroud over the Electric Submersible Pump increases the fluid bypass velocity alongside the submersible motor for the required cooling. This shrouded Electric Submersible Pump configuration is conventionally used where the production flow rates within the wellbore are insufficient to generate the fluid bypass velocities necessary for optimum motor cooling. The Y-tool in other completions allows access for any type of wireline or Coiled Tubing-conveyed intervention for surveillance and and/or treatment operations. Previously, if a completion required a shrouded ESP, conventional Y-tools were precluded, due to the limitation of the production casing inner diameter. A specialty Y-tool was designed to accommodate conventional bypass tubing that has sufficient internal clearance for standard wireline tools together with a crossover adapter for the ESP shroud.This combination of conventional bypass tubing and Electric Submersible Pump shroud in the same wellbore, is limited to 9 5 ⁄8Љ casing where the shroud outer diameter and the bypass pipe outer diameter must have sufficient clearance between each other and sufficient stand-off from the inner diameter of the production casing. The Electric Submersible Pump shroud ensures optimum motor cooling and extended system run life, especially at lower flow rates.This innovative technology is now scheduled to be standard equipment in all Electric Submersible Pump completions in production casings with Outer Diameter equal to or greater than 9 5 ⁄8Љ. Diagnostic wireline and Coiled Tubing-conveyed surveys, remedial and stimulation treatments can now be performed thru-tubing in Electric Submersible Pump completions without costly rig workovers. The availability of these services affords timely intervention to arrest increasing watercuts in Waterflood offtake producers thereby reducing the overall baseline production decline rate.
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.
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