An Enhanced Assembly for Management of Open Hole Deepwater Standalone Screen Injector Completions

A major operator with two large projects in Africa has been using a unique subassembly design, called the dual-isolation assembly (DIA), positioned on the bottom or toe of an open hole stand-alone screen (SAS) completion. The main objective of the DIA is to enhance the circulation process for washdown capabilities and provide efficient management and removal of the filter cake for the subsequent improvement of injectivity rates by lowering formation skin values on the injector wells. After providing high-rate washdown through the float shoe at the toe of the completion, the DIA provides a means of circulating a filter cake removal treatment for the open hole. Once the filter cake treatment has been circulated sufficiently, the service tools are retrieved from the completion to surface. For an injector well, the flow path into the formation would be through the sand-control screens and the float shoe from the inside. Since the float shoe incorporates spring-loaded valves that would normally open during injection and close when pumping stops, it is beneficial to lock the valves out of service to prevent long term spring fatigue that could cause the valves to remain open at some point during the life of the well, allowing flow back of formation material inside the screens. After treatment of the open hole, an additional function of the DIA is to close the barrier isolation valve to isolate the formation while the filter cake treatment is activating. As a continuation of an earlier paper (Roane, et al. 2018), the DIA has met all expectations on all 19 wells where it has been implemented in Africa. Due to enhanced procedures, the mechanical skins have averaged 2.5 and injectivity indices have averaged above 140 (B/D/psi) on these wells. Installation times have continually improved during the project due to following best practices. In addition to fulfilling the requirements of these standalone screen (SAS) completions, the DIA design addresses other potential challenges, such as the prevention of hydraulic locks and formation swabbing, which can be detrimental and problematic to open hole completions. Other characteristics of the DIA that benefit open hole management were realized during the course of the project, such as the capability of the DIA to wash through the interior of the isolation barrier valve prior to closing the valve. Once closed, the valve can be re-opened and re-closed as required. An important aspect of the physical attributes of the DIA that benefits logistics and running speed of the completion is its compact design allowing it to be completely assembled in the shop and shipped to location, such that it is a single pickup and makeup on the rig floor. This benefit has been exhibited by continual improvement in completion installation times throughout the project.