Neptune Spar Topsides Modifications

Fast-track engineering and construction management for spar expansion project completed on schedule while facility remained in operation.

Client:

Kerr-McGee (now Anadarko Petroleum)

Location:

Viosca Knoll Block 826, Gulf of Mexico

Project Scope:

The Neptune Spar was installed as a hub in approximately 1,930 feet of water in Viosca Knoll Block 826, offshore Louisiana. Mustang provided front-end engineering design, detailed engineering and construction management for the expansion of the facilities and supporting structure to accommodate a 30 MMSCFD gas flow capacity increased through an approximate 14-mile tie-back to the Swordfish field. The existing deck had limited physical and weight expansion capability, requiring significant deck structural strengthening to support the deck extensions. While the spar was able to handle additional topsides weight, the additions needed to be strategically located to maintain the vertical and horizontal centers of gravity. During the project and before it could be commissioned, the platform experienced a direct hit from a major hurricane which damaged the facility and significantly impacted the tie-back project.

The expansion included the installation of two major modules and multiple other segments such as a compressor module with two centrifugal compressors boosting pipeline sales pressure and a new production module with three production separators added on a cantilevered extension. Deck extensions were also required for an allocation metering skid, flowline heaters and a pigging launcher/receiver. A new stainless steel flare scrubber was added, along with an independent firewater system, two 400 bbl methanol storage tanks, chemical injection skid, motor control center and a programmable logic controller. Much of the existing equipment was overhauled, modified or replaced. Overall, more than 25 module sections were installed, totaling more than 850 tons of equipment and piping.

Replaced equipment was demolished and offloaded from the facility to the supply boats in a proper sequence, working in tandem to coincide with erection of new equipment. Adding to this challenge, the work was executed so as not to interfere with operations and ongoing repairs stemming from facility damage caused by Hurricane Ivan.

During hookup, more than 60 pressurized and fire-retardant welding habitats were constructed onsite to facilitate continual facility operation and maintain existing production levels. Thorough safety and environmental plans were developed, as well as scenario analyses and emergency planning. Because no 3D drawings were available of the existing platform, physical measurements were taken and entered into 3D PDMS modeling software to eliminate clashes from the network of new and existing piping runs in a minimally expanded footprint.

Client Benefits:

• The flare-tip was replaced, at a considerable cost savings, by utilizing a specialized jib boom attachment.
• Minimal rework was required and necessary revamping of the existing reciprocating compressor and scrubber, piping tie-ins and leak testing were all completed within a scheduled 24-day turnaround at the end of the project.