The North Platte field is located offshore Gulf of Mexico (GoM) about 170 miles south of Louisiana in the Garden Banks in water depths ranging between 4,250 to 5,000 feet. The development plan included initial production from four drill centres tied back to a semisubmersible Floating Production Unit (FPU) using four flowlines and Steel Catenary Risers (SCRs). Allowance for future tiebacks are included in development plan.
The main challenge in this project was the high-pressure reservoir (20K) and its potential compartmentalization. It was one of the determining factors between developing a tieback to existing facility and a new stand-alone floater in the concept selection phase. The topside processing facility needed to be efficiently designed for the high pressure while reducing weight but, at the same time, allowing for the flexibility of Enhanced Oil Recovery (EOR) without significant impact on the initial CAPEX so that a business case can be established so the project became commercially feasible. The high-pressure reservoir requires significant increase in the riser wall thickness. Flexible top termination joint at the interface with the hull becomes not feasible and a stress joint was required. For a feasible riser solution in this project a significantly reduced semisubmersible motion response was required.
Intecsea supported the client in the concept select design and the pre-FEED bid documentation of this project. The team methodically started addressing the challenges by communicating with equipment vendors to identify a potential qualified equipment supplier, and then, with the client, challenged and openly discussed the sparing philosophy to optimize the process system and weight. Several EOR options were investigated. The execution cost, schedule, and potential shutdown to install the future EOR was optimized vs. the required pre-investment to select the winning option. Building on our extensive experience in similar recent projects in the GoM, an improved semisubmersible hull design with motion friendly for the SCR was achieved.
Intecsea also seconded subject matter experts to be part of the client integrated team to support design key decisions, prepare project functional specification, basis of design, and FEED and EPCI scope of work. Intecsea also managed the bidding process with the five EPC contractors involved.
An efficient and feasible topside design for high pressure with optimum pre-investment for EOR was achieved. Lightweight hull design with motion friendly to support the challenging heavy wall risers was developed.