SS Delta House - Topsides Design Philosophy
Authors: Taylor J. Denis , Foret Robert , Buchert Sharon 
Published: April 2015

The Delta House FPS design/fabrication objective was to complete a subsea well processing platform to be installed in roughly 30 months after project sanction. Project execution philosophy was based on a design while build concept which facilitated the aggressive schedule. The platform was installed in Mississippi Canyon, Block 254 with a water depth of 4500 feet. The hull which was designed by EXMAR Offshore was based on the OPTI 11,000 concept which allowed for 11,000 metric ton topsides payload. The design production rate is 80,000 BOPD, 200 mmscfd, and 40,000 BWPD with a peak production capacity of 100,000 BPD and 240 mmscfd. All production, treating, utility and control systems were designed for simplicity and reliability while meeting the regulatory requirements of the Bureau of Safety & Environmental Enforcement (BSEE), the U.S. Coast Guard, & DNV, as well as meeting the sales specifications of the receiving pipeline companies. An additional 500 metric ton payload capacity for the platform was another design parameter in order to add future equipment.

LLOG Exploration envisions using the OPTI 11,000 concept on future developments with minimal design modifications. This philosophy will reduce the time between final funding and platform installation.

The Delta House FPS is based on a single deck design in which most process and utility skids were placed on the main (upper) level. One of the main design objectives was to be able to lift the completed topsides deck with Kiewit's Heavy Lift Device (HLD) which has a nominal capacity of 10,000 short tons. This philosophy allows for fabrication and hook-up work to be performed while the deck is on the ground, allowing for easier access for construction personnel and use of fabrication yard cranes for moving equipment. The single deck concept was used to minimize design and fabrication time as well as allowing for easy process modifications on future platforms. LLOG Exploration's design philosophy for future FPSs is to use the same utility systems as approved by DNV while tweaking the processing equipment as necessary due to new PVT data and new departing pipeline specifications.

Delta House design, fabrication, and integration took roughly 30 months to complete from project sanction to sail away from Ingleside, Texas. During this period the topsides design team had to accommodate a change in the PVT data once a well fluids sample was received and analyzed. The production process equipment was re-evaluated which resulted in the addition of a condensate stabilization unit required to meet the oil sales pipeline RVP specification.

The goal of lifting the entire topsides by the HLD was accomplished and the results from the incline test showed that the platform has an additional capacity of approximately 1000 metric tons for future equipment. This additional capacity may allow for the addition of new systems (i.e. waterflood or amine treating) or additional subsea tiebacks.

The design philosophy of the Delta House platform allows for flexibility in production handling while meeting processing, metocean, and regulatory requirements. The platform design and fabrication schedule allow for a quick turnaround from field discovery to production.

This paper will explain the basis for the design philosophy, why certain topsides equipment were used, and what modifications were made during the design and fabrication of the facility.