Ultra Deepwater Dry Tree System for Drilling and Production in the Gulf of Mexico, Phase 1

07121- DW1402b

Goal
This project will assess alternative dry tree semisubmersible (DTS) concept designs for two different payload cases in accordance with an agreed upon basis of design, and select one hull form option for model testing and further development in a Phase 2 project. The intent is to investigate the feasibility of developing this platform design and to identify any technical limits to areas where further qualification or testing will be required. (Note: This project is one of two parallel efforts. The other, Project 07121-DW1402a, conducted by another team led by FloaTEC, LLC, has been completed.)

Performers
Houston Offshore Engineering (HOE), Houston, TX 77079
Keppel Fels, Singapore 629351
Kiewit Offshore Services, Houston, TX 77064
Offshore Technology and Research Center, College Station, TX 77845

Background
As Gulf of Mexico field development is rapidly moving to deeper waters, the available alternative platform concepts for dry tree drilling and production operations are limited. Without dry tree access, oil and gas production becomes subject to the availability and high cost of mobile offshore subsea drilling units, which in the current market are difficult and expensive to contract. Currently, the deepest tension leg platform (TLP) installed to date (Conoco’s Magnolia platform) is in 4,674 ft of water, whereas the Perdido spar currently under fabrication is designed for installation in 8,000 ft water depth. As patent ownership for the truss spar limits the competition for spar platform developments to two companies, a competitive dry tree floating structure design (e.g. semisubmersible) is a needed option to provide greater flexibility for deepwater operators in making development decisions.

This project proposes to develop an ultra deepwater dry tree system concept for drilling and production in the GOM. The approach is to focus on an improved semisubmersible hull form that provides global motions compatible with conventional riser tensioning equipment and systems. The proposed hull concept will be comprised of conventional hull structural components, will not require any unusual installation/integration methods (e.g. moving or jacking components and mechanisms), and will have been shown through global performance analysis to provide acceptable motions.

This Phase 1 project will develop payload and platform configurations for two study cases. The objective is to develop the configuration and perform a high-level assessment in terms of global motions, riser strokes, and constructability to support the decision making necessary to determine which concepts will continue into Phase 2. The project will develop the floating system concept, validate the concept through engineering analysis and model testing, and focus on engineering that will lead to rapid commercialization of the concept.

Deliverables will include: coordination and management deliverables, including progress reports, meeting minutes, meeting presentations, work shop documentation, quarterly RPSEA reports, etc.; a design basis that provides a clear description of all input data and design criteria used to develop the platform design; summary documentation of the platform configuration, including a sizing basis table, a key figures parameter table and a key figures sketch; conceptual drawings of the hull, mooring, topsides and riser systems, including arrangements, principal dimensions, etc.; analysis reports to document that validation analysis has been performed; model test specification, model test basis report and model test correlation report; weight reports; an execution plan summary, including delivery model cost and schedule; and a Phase II plan including recommended activities and deliverables.

Potential Impacts
The existing dry tree concept for deepwater displays significant challenges and risks, including offshore integration, limited and congested wellbay area, and limited facilities for hull fabrication and transportation. This project will accelerate the development of an alternative dry tree semisubmersible design that can be cost competitive with the current Spar alternative. This floating structure will utilize existing technology to accommodate large payloads, be permanently moored in deeper waters, and provide the global performance characteristics required for successful operation of a dry tree unit. More rapid development of such a technology will provide deepwater operators with greater flexibility in making development decisions, and will lead to more rapid production of domestic deepwater offshore oil and gas resources. A new dry tree system for ultra deepwater GOM has the potential to increase total reserve recovery for the United States and lower the overall cost for extracting hydrocarbons from beneath the sea floor.

Accomplishments
All of the technical work planned for Stage 1 is completed. This includes the topside layouts, riser configuration, hull sizing, execution plan, cost estimates, and the workshop presentation and meeting. Stage 2 planning has been completed; this includes project management plans, a schedule, and an expenditure plan. The wind tunnel testing has been completed with positive results. The design basis and configuration were updated for 1,000 year environmental conditions. Following this update, the wave basin test specification was completed.

Current Status
The key tasks to be undertaken following the submission of the Project Management Plan and Technology Transfer Plan are outlined below.

1. Develop Basis of Design for Two Study Cases. Subtasks include reviewing project team input data and ensuring all parties agree to the basic parameters, developing high-level topsides arrangements/payloads, drilling rig arrangements/payloads, top-tensioned riser system arrangements/payloads, risers and flowlines arrangements/payloads, and umbilicals for two study cases, and developing wellbay layout and review feasibility.

2. Develop Hull and Mooring Configuration and sizing for Two Study Cases using the Houston Offshore Engineering Paired-Column Semisubmersible concept. A discussion without calculations will be sufficient for marine stability issues associated with the hull designs in this phase of work.

3. Perform High-Level Global Performance Analysis for Critical Cases (Motions and Offsets).

4. Perform High-Level Top-Tensioned Riser Analysis (Stroke, Strength and Tensioner Stiffness requirements).

5. Perform High-Level Constructability Review for Hull Structure and Topsides Integration. For commercialization, the concept must be perceived as mature. Maturity is achieved by having world class fabricators review hull constructability and world class topsides integration facilities review platform integration. Additionally, an execution plan for delivery of the complete facility will be developed..

Keppel Fels has been selected to provide input on hull constructability. Kiewit Offshore has been selected to provide input on topsides integration. The hull constructability and topsides integration activities will be formal and structured. The tasks will include preparation of drawings and specifications that will be transmitted to the participating companies (Keppel Fels and Kiewit) where the deliverables will be reviewed by in-house technical teams. A constructability log will be managed to capture inquiries and suggestions from each company with the final design resolution, which will be implemented in the final design at the end of Phase 1.

6. Compare Calculation Results to Design Criteria.

7. Prepare cost estimates.

8. Summarize Results in a Stage 1 Summary Report, Workshop, and Presentation.

Project Start: December 30, 2008
Project End: December 31, 2009

DOE Contribution: $812,042
Performer Contribution: $235,856

Contact Information:
RPSEA – Jim Chitwood ( jchitwood@rpsea.org or 713-372-2820)
NETL - Jay Jikich (Sinisha.Jikich@netl.doe.gov or 304-285-4320)
Performer Company –Philip Poll (ppoll@houston-offshore.com or 281-436-6203)

Additional Information

Stage 1 Final Report [PDF] November, 2009

Stage 2 Final Report [PDF-3.43MB]