A Flexible Approach To Well Abandonment

OIS completes 17th multi-operator campaign.

Well abandonment is a key challenge for the UK’s oil and gas industry. The UK Department of Energy & Climate Change (DECC) is actively engaging with operators to ensure that suspended exploration and appraisal wells, and open-water shut-in production wells are permanently abandoned in an acceptable time frame and manner.

Operators are obliged to work with DECC’s Offshore Environment Unit and, to fulfil their decommissioning responsibilities, they can face an array of challenges, including securing internal budget, allocating limited internal resources and expertise to non-revenue generating projects, and gaining approval from partners whose appetite to complete abandonment operations may differ from that of the operator.

In November 2013, OIS completed its 17th multi-operator well abandonment campaign in the North Sea. During this operation, six subsea wells of varying categories and at various depths were abandoned on behalf of three different operating companies. For this latest campaign, OIS provided integrated project management throughout the on- and offshore operations.

This campaign builds on a strong record of success as Tom Selwood, vice president – commercial and business development at OIS, explains, “Over the past 18 years, OIS/Acteon Group has abandoned 116 wells of varying categories on the UK Continental Shelf for a wide range of operators. We are immensely proud of the fact that, in this time, we have completed the decommissioning operations without a single lost-time incident.”

The offshore operations for the 17th campaign were conducted in two phases from the Siem Stork, an OIS-chartered multipurpose field and remotely operated vehicle support vessel. Selwood takes up the story: “During the first phase, we used the award-winning* suspended well abandonment tool (SWAT), a technology owned by Acteon sister company Claxton Engineering Services Ltd and offered exclusively to the market by OIS. The SWAT system is designed to permit perforation, circulation and cementation of multiple casing annuli and has been used to abandon more than 80 Category 2 subsea wells on the UK Continental Shelf. The tool is landed on the wellhead and controlled from the surface through an umbilical.

“We deployed the SWAT through the vessel’s moon pool,” Selwood continues, “and used it to circulate out drilling fluids and set cement plugs across the casing annuli of the wells. In the second phase, we conducted abrasive severance operations for wells in water depths ranging from 70 to 150?m. This phase included the safe disposal of all the recovered subsea structures and waste materials.”

As in previous years, OIS’s flexible approach helped to keep the project on schedule. Adverse weather conditions encountered in the northern areas meant that there were times when the vessel's crane could not operate safely. When this was the case, OIS moved initial project activity to the southern worksites to work around the weather window without compromising operational efficiency.

“As is usual under the multi-operator approach, OIS managed many of the key logistical, quality, health, safety and environment, and reporting tasks, such as developing the detailed operational procedures; organising vessel charter and management; providing quality, health, safety and environment support; performing all project reporting and accounting; and preparing the end of well reports,” Selwood explains.

Vessel versus rig
OIS’s vessel-based solutions help operators to meet their well abandonment obligations in a safe and environmentally responsible manner. The multi-operator model, which enables operators to share certain project costs, combined with a rigless approach to the abandonment work, also provides a much more cost-effective decommissioning process when compared with rig-based alternatives.

The day rate for a vessel, including fuel, is approximately 30–40% of the costs associated with securing a rig, but the potential for cost savings is not the only factor that prompts operators to choose a vessel-based option. Project planning and scheduling for well abandonment are strongly influenced by equipment availability. Projections for the period up to 2016 suggest that there will be extremely limited rig availability in the North Sea region and that could cause a bottleneck for any new projects being planned today.

In contrast to semisubmersible, jackup or drilling rigs, which require positioning and moorings, vessels can move quickly between distant worksite locations and conduct operations using dynamic positioning. This additional flexibility makes a key contribution to time savings and adds considerable flexibility to the campaign schedule.

More than plugging and cutting
OIS’s contribution to the programme extended beyond the purely technical aspects of well abandonment. Selwood continues: “In addition to the actual abandonment operations, we assisted the operators in preparing the necessary environmental data relating to abandonment and securing the relevant permits. These included requirements such as the oil pollution emergency plan, PON 5 (application to abandon a well) and PON 15f (permit to use/discharge chemicals during well abandonment) applications, and the Marine and Coastal Access Act licence.”

Collating and presenting the necessary environmental information in an appropriate form can be time consuming and relatively complex. The schedule must accommodate the review process and the time required to gain consent from the regulatory authorities. For example, gaining consent for the oil pollution emergency plan can take up to 60?days from submission; the PON 5 consent can take up to 21 days; the PON 15f consent can take up to 28 days; and new applications for a Marine and Coastal Access Act licence can take several weeks.

“At OIS, we are familiar with all the legal requirements for abandonment operations on the UK Continental Shelf and can provide as much or as little support as our clients require,” Selwood concludes.

*Queen’s Award for Engineering Innovation and Petroleum Institute Platinum Award.

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