Cascade and Chinook Subsea Development: the World

Abstract

Located in 8,200 feet water depth, the Cascade & Chinook subsea development risers are the deepest production risers in the world. These are also the first offset free-standing hybrid risers to be installed in the Gulf of Mexico, and the world's first use of hybrid risers in combination with a disconnectable turret-moored FPSO.This paper presents the unique benefits and challenges associated with using hybrid riser tower technology in the deepwater Gulf of Mexico, based on the experience gained by both client and contractor in executing the Cascade & Chinook riser project.The authors review the history of the Cascade & Chinook riser system, from concept selection through engineering, procurement, construction, installation and pre-commissioning. The most significant challenges and the key project management decisions are highlighted, covering: field layout considerations; strength and fatigue performance; design verification; interfaces with the production facility and subsea infrastructure; procurement and fabrication logistics, and spare materials philosophy; installation engineering and execution; safety and quality management; and regulatory compliance. The project management strategy, and the relationship between client and contractor through the project life cycle, are presented and critically assessed.The paper concludes with an evaluation of the delivery time, cost and project execution risks associated with the hybrid riser concept, and compares this with more traditional deepwater riser solutions, in the context of a deepwater Gulf of Mexico development. OTC 21857"bottom current", which actually extends over several thousand feet up from the seabed, is important with respect to vortexinduced vibration (VIV) and umbilical-to-riser clashing. Figure 1: Cascade & Chinook Phase I Concept SelectionThe Cascade & Chinook development will utilize an FPSO that can be disconnected from the mooring system 6 . This allows the FPSO to sail away from the danger of approaching tropical storms or hurricanes. When released, the disconnectable turret buoy descends to a neutral depth of more than 120 feet below sea level where it, together with the connected mooring lines, risers and umbilicals, are sheltered from the extreme wave forces of such storms.Production facility type and water depth are generally two key parameters for riser concept selection and this was the case for Cascade & Chinook, i.e., the deepest risers in the world combined with a disconnectable turret-moored FPSO. At the time of concept selection, flexible pipe was not qualified for the water depth. While steel catenary risers have been successfully used with semi-submersible and spar hulls in the Gulf of Mexico, and with spread-moored FPSOs in West Africa, they were considered to present too much risk for the Cascade & Chinook project for the following reasons.• Early studies of fatigue performance, and review of literature investigating use of SCRs with an FPSO in the Gulf of Mexico 7 , indicated that it might not be possible to achieve the required s...

WITHDRAWN: Global CO2 Storage Potential of Self‐Sealing Marine Sedimentary Strata

“…Similar additional potential exists in the U.S. Gulf of Mexico. The complex evolution of the strata within this basin has included the deposition of large sand bodies [ Watkins and Drake , 1982], a number of which have been found to contain “giant” (500 million barrels of ultimately recoverable oil or gas equivalent [ Halbouty , 2003]) oil and gas fields, such as the Thunderhorse and more recently Cascade and Chinook fields [ Halbouty , 2003; Brantly , 2007; Masson et al , 2011].…”

Global CO2storage potential of self‐sealing marine sedimentary strata

“…Similar additional potential exists in the U.S. Gulf of Mexico. The complex evolution of the strata within this basin has included the deposition of large sand bodies [ Watkins and Drake , 1982], a number of which have been found to contain “giant” (500 million barrels of ultimately recoverable oil or gas equivalent [ Halbouty , 2003]) oil and gas fields, such as the Thunderhorse and more recently Cascade and Chinook fields [ Halbouty , 2003; Brantly , 2007; Masson et al , 2011].…”