Oil major ConocoPhillips has submitted its draft decommissioning plan for the subsea infrastructure and associated infield pipelines from the MacCulloch field, which is located in the UK North Sea, to the UK authorities.
The MacCulloch field is in the UK Central North Sea (CNS) Block 15/24b, in a water depth of 149 meters. Developed in 1996/97, the field had an expected life of ten years. Production started via the FPSO North Sea Producer in August 1997. The vessel was owned by the North Sea Production Company (NSPC).
MacCulloch production was via two drill centers, West (WDC) and East (EDC), located 1.6 km and 2.9 km to the West and South East of the vessel location, respectively.
Oil and gas were exported from the FPSO vessel to the Repsol Sinopec-operated Piper Bravo platform through its owned 10” oil pipeline and 6” gas pipeline.
Preparation for decommissioning of the MacCulloch field started on May 3, 2015. The first phase of decommissioning continued until August 2015 when the North Sea Producer, the FPSO vessel, was removed from the area. Thereafter, the vessel was taken to Teesside by the owners for reuse and recycling.
During this initial decommissioning phase, the pipelines were flushed and made hydrocarbon free and the risers and mid water arches were retrieved for recycling/disposal.
In 2017, all of the wells were suspended with two isolation barriers using a light well intervention vessel, the Helix Well Enhancer.
The remaining decommissioning process for the MacCulloch assets will be achieved by the removal, dismantling and disposal of subsea facilities and the well plugging and abandonment program.
According to ConocoPhillips’ decommissioning plan, all subsea installations are to be recovered to shore for reuse or recycling and all wells will be plugged and abandoned. Furthermore, all pipelines will be recovered to shore for reuse or recycling and all concrete mattresses and grout bags will be recovered to shore for re-use or recycling. Finally, all anchor chains will be recovered and returned to shore for reuse or recycling and all anchors will be decommissioned in situ.
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