Objectives/Scope Downhole Annular Barrier (DAB) systems employed in intervention can correct integrity and conformance control issues during well lifecycle, extending the productive term in a safe and costeffective manner. These emergent wireline technologies come with unique challenges for logistics, quality control, and engineering, but can also provide solutions to difficult problems, with high value to spend ratio, in the non-rig intervention sector. The paper will review one such successful intervention, completed offshore Trinidad W.I., in a gas well presenting long term Sustained Casing Pressure (SCP). The desired end state of the well was A-Annulus at 0 psi SCP, which would return the well to a safe state and permit a planned infrastructure project to move ahead. Methods, Procedures, Process Operational objective was isolation of the casing annulus pressure from the source by injecting epoxy into the annular space at depth, forming a 360-degree pressure barrier. The project can be broken down into three main sections. The paper and presentation will address each section with its specific challenges, learnings, and outcomes: Onshore Epoxy and Tool Preparation Each Downhole Annular Barrier job employs a custom recipe epoxy suited to the planned logistics timing and expected bottomhole conditions. Quality control of the epoxy recipe and mixing process as well as temperature control of the batch after mixing is key to the sealing properties of the final epoxy plug. • An Epoxy Lab and Mixing Station was dismantled, air freighted, and reconstituted in Trinidad near to the field operations port. Special insulated offshore CCU were built to transport and contain filled epoxy canisters while maintaining low temperature requirements (near to 0 deg C for up to 30 days). • Build and System Integration Testing (SIT) of the downhole system (anchoring, stroking, hydraulic testing, perforation, and injection) with the electric line system (conveyance, telemetry, power). Offshore Job Execution The DAB system employed is designed to complete multiple operations in a single trip into the well, including perforating and high-pressure epoxy injection, with precise position control and monitoring. This is made possible with the multi-function modular tool. The operation was dynamic by design and contingencies were implemented based on the well response. Multiple epoxy annular plugs were placed into the A Annulus at depth, with high pressure injection. Results, Observations, Conclusions Well Response and Assessment Utilizing advanced annular surface monitoring technology and PvT analysis, precise assessment of the annulus pressure build was recorded throughout the operation. Once the project criteria were met, the operation was successfully concluded.
An openhole gravelpack (OHGP) gas well was planned as part of an infill drilling campaign on a mature Norwegian Continental Shelf field. A geological pilot hole unexpectedly identified a significant pressure differential between two reservoir intervals. This paper describes an innovative modification of the lower completion, within a short turnaround time, in order to manage the clean-up of the reservoir intervals and limit crossflow. Calculations based on the pilot hole results predicted that the low pressure reservoir would not flow until there was significant depletion in the high pressure reservoir. This risked formation damage due to delayed clean-up. Additionally, there was potential for very high crossflow rates that risked mechanical damage to lower completion equipment and/or causing formation damage. There was insufficient time to completely redesign the completion. A solution, supported by simulations, showed that a fixed choke in the lower completion would enable immediate clean-up of both reservoir intervals. Additionally, aplug had to be set in the gravel-filled annulus to prevent flow diverting around the fixed choke. These modifications would reduce the potential crossflow rate to an acceptable level. The OHGP was performed as originally planned. A wireline tool was run to inject an epoxy resin plug into the gravel and the fixed choke was then set at the same depth. The well was cleaned up as planned to the drilling rig, with both reservoir intervals observed to be producing. The choke toolstring included an additional flow area that automatically opened after a pre-defined time delay. Simulations predicted the pressure differential at this time to be significantly lower. Reducing the choking effect in this way, once the risks from crossflow at the start of well life had been minimised, avoided hindering production in later well life. The well has performed as expected with no indications of production impairment having occurred, despite the initial period of high differential pressure between the reservoir intervals. This is believed to be the first injection of epoxy resin into a newly completed gravelpack. Coupled with the implementation of the two-sized choke it has been possible to manage a problematic reservoir pressure differential in a new well without resorting to costly and lengthy redesign of the completion.
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