Solution becomes new P&A benchmark in offshore field
Challenge – In the field, the platform had been unmanned and the drilling facility idle for 10 years,
requiring costly upgrades to be prepared for the plug and abandonment (P&A) campaign. The P&A solution had to comply with strict environmental and internal company technical requirements, and also reduce overall decommissioning time for the platform. The customer set a 60-person maximum for onboard personnel in order to save large reinstallation costs. Traditional platform solutions for this type of operation would require 100 people on board. Achieving project results with this limited personnel would be a challenge.
Solution – Through close collaboration with the customer, Halliburton took an active part in the development of the overall P&A strategy for the project, analyzing the needs for downhole tool conveyance and focusing on solutions requiring minimum topside equipment. The wells were categorized based on completion type and technical status, and a plan to execute the P&A scope with as little surface equipment and personnel as possible was made in compliance with regulatory and customer technical and safety requirements. Halliburton used a phased approach that allowed placement of the barriers at the lower day rate compared to a traditional platform drilling rig solution presenting large cost savings to the customer. Phase 1 and Phase 2 in the customized solution did not use a traditional rig approach. The rig was not included until Phase 3. The phased approach also gave the customer the opportunity to revise the plan in between the phases and eliminate risk to the project based on learnings from the wells – reducing the overall P&A project cost. This approach also enabled the project to be less schedule-driven than normal, as breaks between the phases could be adjusted as required in the event optimization of the plans were needed. Additionally, the phased approach allowed executing as much of the scope as possible at the lowest possible daily cost.
The execution of the project was split into three phases:
Phase 1: A wireline campaign on 10 wells to assess the technical status of the wells and confirm the correctness of the well data was conducted. The wells were also prepared for the subsequent phases by bullheading fluids into the reservoir. This campaign confirmed correctness of well data that was then used to determine future actions in the overall plan.
Phase 2: A coiled tubing campaign was conducted in order to effectively place the reservoir barriers through the production tubing. The coiled tubing placement eliminated the need to pull the production tubing from these wells, thus saving time and cost. The campaign included a qualification process of the barrier placement method, using Halliburton tubing-conveyed perforation (TCP), along with Pulsonix® Tuned Frequency Amplitude (TFA) service and AbandaCem™ cement technologies.
Phase 3: A purpose-built P&A unit was designed, constructed, and commissioned in parallel with the execution of phases 1 and 2. Upon completion of Phase 2, the modular P&A unit was installed at the platform and the operation commenced. During Phase 3, the P&A unit would place the reservoir barriers on the wells, where production tubing had to be pulled from the wells in order to place the barriers in accordance with regulatory requirements. The P&A unit was also used to place the environmental barriers in the top section of the wells.
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