SUBSEA PRODUCTION TECHNOLOGY Production from Enserch's GB 388 Project Underway

Production gets underway on Enserch's GB 388 floating semisubmersible producer in the US Gulf of Mexico.

Enserch Exploration began development of the Garden Banks 388 Project in 1993. This project consists of six major components: the floating production facility (FPF), a 24-slot subsea template, a free-standing production riser, two 54-mile, 12-in. product export pipelines, the shallow water facility (SWF), and two sales pipelines.

The FPF is designed to conduct simultaneous drilling and producing operations. Production capacity is 40,000 bbl of oil and 120 MMcf/d of gas. The 24-slot template is located below the FPF on the seafloor at about 2,150 ft. The free-standing production riser system connects the template with the FPF, and it consists of a bundle of 48 3-in. flowlines, two product export lines, and the subsea control umbilicals.

Two 12-in. export pipelines run parallel for 54 miles connecting the template with the SWF, transporting the produced oil and gas separately. Produced gas is dehydrated to less than 4 lbs/MMcf at the FPF. The SWF is a fixed platform designed to meet the 1% BS&W oil specification and compress the gas prior to introducing the product into the sales pipelines.

The 8-in. oil sales pipeline is about two miles long and ties into a Texaco trunkline, and the 12- in. gas sales pipeline is about 2,000 ft long and ties into a Sea Robin trunkline.

Team philosophy

In building the Garden Banks 388 project team, several engineering disciplines and consultants were brought together. The Enserch Exploration operations group was included as a team member, and as with past projects, played an integral role in the project development.

The benefits of including operations personnel in the early stages of the project were numerous. They provided practical hands-on experience to the team, assisted in the selection of equipment, helped save money by eliminating unnecessary equipment expenditures, and helped guide the design and operating philosophy.

This practical input optimized equipment selection and layout, allowing operations personnel to become intimately familiar with the project and facilities, leading to a smoother transition from projects to operations, and ultimately, a successful start-up.

On the Garden Banks 388 project, operations representatives were involved in many aspects of the development, including participation in the design of the subsea template, floating production facility, shallow water facility and pipelines. Also, they were involved in contract negotiations and bid evaluations and played a key role in the development and implementation of procedures for pipeline commissioning, systems integration testing, factory acceptance testing, precommissioning, and start-up.

Having developed precommissioning and start-up programs in the past, Enserch felt that the project would benefit from the operations representatives technical experience. In addition, because people have been the main resource in this endeavor, the company concentrated on making individual participation a rewarding experience.

In April 1994, while the project was into the advanced stages of the detailed design and the fabrication of most major equipment was underway, Enserch began to implement the strategy for precommissioning and startup. The company maintains a relatively small project group, therefore contract personnel were added to the project team to represent Enserch by assisting in the execution of different phases of the project.

A consulting engineer, who was already familiar with the organization from a previous project, was assigned to work with an Enserch operations supervisor in the preparatory work for precommissioning and start-up. Working together, they became operations representatives for the Garden Banks 388 project and equal commitment was assumed by these individuals for the task ahead.

(Left) The subsea systems for the GB 388 floater are shown in this drawing. The distance between the floater and the fixed platform are collapsed to show the configuration.

(Right) Systems integration tests of the subsea pig launcher and template were conducted before launch.

Task preparation

Initially, detailed precommissioning and start-up plans, including schedules, were prepared and presented to Enserch Exploration's project management. Upon review and approval, the plans were implemented. Later in the project, participation in the pipeline commissioning activities became part of operations' responsibilities. Again, Enserch's management endorsed the proposed plans.

Upon approval, plans were executed by grouping people who could contribute to the completion of the various tasks. A list of major tasks involving direct participation of the operations representatives included:

• Review of all project drawings and specifications.
• Preparation of scope of work for contractor to prepare detailed documents for the FPF and the SWF, including precommissioning procedures manual, purging and initial start-up procedures manual, and start-up and operations manual.
• Bid analysis and recommendation for contractor to do above work.
• Expediting of vendor data in order to keep contractor's work on schedule.
• Reviewing and approving contractor's preliminary issues of manuals.
• Organizing the manuals and the equipment data books being prepared by other contractors in order to make them easy to refer to during precommissioning and start-up.
• Inspection of equipment packages at vendor shops (factory acceptance tests).
• Inspection of interconnecting work at fabrication sites (systems integration tests).
• Selection of spare parts for production equipment.
• Review of proposed pipeline commissioning procedures.
• Selection of pipeline commissioning contractor.
• Systems integration tests of subsea template.
• Onshore execution of SWF precommissioning.
• Offshore execution of FPF precommissioning.
• Nitrogen purge of both facilities.
• Hydro-testing pipelines.
• De-watering gas pipeline with nitrogen.
• De-watering oil pipeline with crude oil.
• Start-up of FPF and SWF.

The commitment and preparation for this project was understood by most team members as well as vendors and contractors. A spirit of cooperation was demonstrated daily by all involved by practicing activities such as concern for everyone's, keeping communication lines open, ensuring that everyone was treated with respect, having two meetings per day which motivated teammates by letting them know daily goals were achieved, and including team members in decisions as much as practical.

The results of practicing this teamwork philosophy include no accidents or injuries to a team member during precommissioning and start-up of facilities and pipelines, meeting the planned schedule of activities at all sites, start-up of systems with relative ease and with minimum problems, team members satisfaction from their participation, and management satisfaction with this phase of the project.

The Enserch Exploration Garden Banks 388 development project began operations in September of 1995. The commitment, preparation and cooperation of every team member made the precommissioning and startup of both facilities, plus the commissioning of the pipelines safe and successful.

Much credit is due the precommissioning and startup personnel, including field supervisors, I & E technicians, mechanics, operators, vendor representatives, and contractors for creating a winning partnership and helping Enserch achieve project goals.

AUTHORS

Ruben H. Silva is a senior consulting engineer with CBS Engineering. He has worked for several engineering, construction and operating companies in projects involving chemical, petrochemical, refineries, and oil and gas production facilities for 29 years.
Mike J. Autin is a senior production supervisor with Enserch Exploration. He has worked for several oil and gas operating and related service companies for 17 years.

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