Track Record...

In order for the Brent A & Brent B platforms to be decommissioned, the Northern Leg Gas Pipeline (NLGP), Western Leg Gas Pipeline (WLGP) and the Far-north Liquids and Associated Gas System (FLAGS) require to be being disconnected from their respective Brent platforms and rerouted via new, subsea facilities.

The project involves the partial decommissioning of these pipelines, the installation of the new subsea infrastructure and the subsequent recommissioning of the pipelines to full operational status.

From initial assessment and concept selection, through FEED and into execution, Chillum Oil has had a pivotal role in this major project. Chillum’s ability to draw on experience gained during the Total MCP01 and Shell Caravel Shamrock projects proved vital for the development of the partial decommissioning and recommissioning philosophies as well as the selection and implementation of the autonomous isolation tools required for NLGP and FLAGS.

Bardolino is a single well subsea development, tied back to the Nelson platform. Production is routed via a dedicated subsea manifold to the Howe subsea facilities two kilometers distant and then onward to Nelson. The subsea manifold also included an Integrated Over Pressure Protection System (IOPPS) to protect the lower rated Howe pipeline and a multiphase flowmeter.

During the FEED phase, Chillum Oil developed the commissioning philosophy for the project and then led the commissioning through the execution phase.

Chillum’s approach to the integration and commissioning of the field-critical IOPPS and subsea control system was to ensure the onshore testing was sufficiently exhaustive to minimise the final offshore commissioning. Not only did this allow a greatly reduced offshore commissioning scope, but also ensured effective early integration into the existing Howe control system.

Chillum Oil also provided the key link between the execution team and the asset operations team during the start-up of the field, guiding the start-up and bean-up of the well from the Nelson control room.

The Curlew FPSO required to be disconnected from the Curlew subsea field to allow it to be sailed to dry dock for essential maintenance and recertification. This involved the complete decommissioning of the infield pipeline & umbilical infrastructure, the partial decommissioning of the gas export pipeline and isolation of the wells and gas export system. Once the FPSO returned to station and was reconnected, the subsea infrastructure was fully recommissioned, including the complete recommissioning of the entire control system.

Chillum Oil personnel have had a long association with the Curlew field, from the original field development in 1997 through to the subsequent Curlew D expansion and Curlew C projects. With this association came an in depth understanding of the complexities of the subsea & topside infrastructure that allowed the decommissioning and recommissioning to be carried out as safely and efficiently as possible.

The Merganser field is a subsea development tied back to the Shearwater platform via the Scoter subsea manifold. The field consists of two subsea wells with production routed to a subsea manifold and into an 8” production flowline to the Scoter Manifold Extension Structure (SMES). From there, produced hydrocarbons are comingled with Scoter production and routed to Shearwater.

From the onshore integration testing of the manifolds, trees and control system through to the final offshore commissioning and start-up, Chillum Oil led the commissioning for the project. Not only was the field brought on stream under budget, but the commissioning strategy minimised downtime of the already producing Scoter field.

The Starling field was developed as a two well tie-back to the Shearwater platform and was further augmented with a third well two years later. The field comprises the three wells with production routed to a subsea manifold and onward to Shearwater through a 12” / 16” pipe-in-pipe flowline.

Chillum Oil managed the subsea commissioning for the project and also provided the interface between the subsea infrastructure and Brownfield modifications to the Shearwater platform. This integrated approach helped the original Starling development to be brought on stream under budget and ahead of schedule.

The third, infill well was drilled two years later to maintain full capacity in the flowline and Chillum Oil were invited to manage the commissioning for this development.

The Caravel and Shamrock fields were developed with two production monotowers. Production from the monotowers is routed into a 16” pipeline, comingling at a wye-piece at the base of the Caravel monotower. Production then flows through the 16” pipeline to a retrofitted 20” wye-piece on the Brigantine to Corvette pipeline at the base of the Corvette platform.

With dual-diameter pipelines and two wye-pieces, this extremely complex pipeline system required a great deal of engineering and planning to ensure the pipeline precommissioning went smoothly. Chillum Oil were onboard the Corvette platform to ensure that partial decommissioning of the existing Brigantine to Corvette pipeline and the subsequent isolation using a series of autonomous isolation tools went without a hitch. The safety of the divers during the tie-in of the 20” wye-piece was of paramount importance and the design, installation, control & monitoring of the autonomous isolation tools was key in allowing the subsea construction to be undertaken.

Recommissioning of the Brigantine to Corvette pipeline and commissioning of the new 16” pipeline from Caravel and Shamrock were combined in an intricate dewatering sequence, allowing the production from both the existing Brigantine platform and the two new monotowers to be brought on stream as soon as possible.

Shell is developing the SWEEP concept as a low-cost method of extracting hydrocarbon gas condensate from marginal fields in the Southern North Sea.

During the Concept Selection and FEED phases, Chillum Oil has been providing innovative solutions for the pipeline and umbilical commissioning to minimise cost and reduce the project schedule risk by removing topside / subsea commissioning interfaces.

The Rhum field is a high pressure, high temperature subsea development, tied back to the Bruce platform. The field comprises three subsea wells with production routed to a subsea manifold via 8” flowlines and then onward to Bruce via a 16” pipe-in-pipe flowline. The subsea manifold also included a High Integrity Pressure Protection System (HIPPS) to protect the lower rated pipe-in-pipe flowline from wellbore pressure.

Chillum Oil were contracted to lead the commissioning during the execute phase, managing the commissioning of both the topside infrastructure associated with the Rhum development and the complete subsea system. Chillum were also retained to provide offshore support to asset operations for the start-up of first two wells.

The Foinaven field was the first UK deepwater field to be developed in the Atlantic margin. The field was developed in two distinct phases and now incorporates thirty-two wells at four distinct drill sites.

Chillum Oil personnel have been involved with the Foinaven field since the subsea infrastructure was first installed in 1996. From 2002 onwards, Chillum Oil has provided pipeline commissioning services for numerous intervention campaigns on Foinaven, as well as the Phase II expansion of the field.

Farragon is a two well subsea development tied back to the Andrew platform via the Cyrus subsea development.

Chillum Oil developed the precommissioning and commissioning philosophy for the bundle pipeline & control tubing system.

In order for the Frigg TP1 platform and the MCP01 platform to be decommissioned, the gas export pipelines required to be rerouted subsea to bypass their respective platforms. The pipelines were partially decommissioned and isolated using autonomous isolation tools to allow the new subsea bypass infrastructure at each platform to be installed and tied in. The re-routed pipelines were then recommissioned to allow full production to recommence. Due to the scale of the project, the work was conducted in two separate campaigns over two years.

Chillum Oil was involved from the early stages of the project, advising on the best decommissioning, isolation and recommissioning solution for the two campaigns. Chillum Oil then led the acceptance testing for the autonomous isolation tools. During the execution phase of the project, Chillum managed the engineering for the decommissioning, isolation & recommissioning on behalf of the installation contractor and lead the offshore execution teams responsible for that scope.

The Skene field was developed as a subsea tie back to the Beryl A platform Riser Access Tower (RAT), via two sequential pipeline & control tubing bundle systems.

Chillum Oil managed the precommissioning of the pipeline and control system precommissioning and commissioning on behalf of the installation contractor.