Consider the remote offshore oil or gas field with minimal or no infrastructure. What is the best choice? Easy. Most operators would go with an FPSO, which offers storage in the hull and direct off-loading to tankers.

But it’s not always as versatile as might be desired.

For example, one of the most economical, simple and robust pieces of equipment in wet-tree applications is the steel catenary riser (SCR), which is a poor fit with FPSOs in most environments because of its relatively high dynamic motion.

In a particularly rich reservoir, an operator will be looking for efficient production, which means deployment of numerous large-diameter risers. That makes finding a riser solution for conventional FPSOs even more difficult.

One answer might be top-tensioned risers (TTRs), which allow direct vertical access to production wells and enhanced recovery. However, the stroke limitation of these risers requires a floating system that provides minimal heave response, so conventional FPSOs, again, need not apply.

An exception would be the incorporation of a wellhead platform to be used with an FPSO, which adds significant capital and operating expenses to the cost of developing a field.

The solution, says Alaa Mansour, Houston-based marine engineering manager for INTECSEA, is a low-motion FPSO, or LM-FPSO. The new design provides advanced motion response which allows FPSOs to be suitable for SCRs and TTRs in harsh environments, while reducing overall development expenses.

The shape of the LM-FPSO hull allows use of a conventional mooring system and eliminates the need for the expensive turret and swivel system and associated operating expenses. The superior motion response results in improved process safety, helicopter operability and onboard habitability.

A five-week comprehensive model testing program at the Korean Research Institute for Ships and Ocean Engineering has confirmed the vessel’s superior performance. Tests were completed on Nov. 18 and the design is now approaching a “Project Ready” status.

—Joseph Markman

Offshore