While the floating liquefied-natural-gas (FLNG) option initially looked promising, high capital expenditure and very high operational expense (OPEX) have limited its potential application, with four potential FLNG projects being canceled in Australasia in the last 2 years. A new solution involving a proprietary hybrid concept has emerged to meet this challenge of developing deepwater gas fields. It is neither surface nor subsea, but the combination of both, offering fundamentally more-efficient and hence lower-cost processing.

Background

Subsea and Deep Water. When the oil and gas industry moved into deeper waters in the 1990s, subsea processing operations were not available. Techniques were developed to prevent hydrates and corrosion, including addition of chemicals such as glycol and monothylene glycol, insulation, and specialized techniques. More recently, this has included heating in the form of direct electric heating or trace heating in specially constructed pipe-in-pipe-type pipelines. These techniques have proved very successful in shallow waters and for moderate tieback distances. However, with the industry moving to deeper waters and greater distance, these same techniques are proving to be too expensive. The lack of first-stage bulk produced-water separation greatly adds to the costs, resulting in large volumes of glycol and water, as well as salt in the glycol, which requires expensive regeneration methods. Long distances are also a key issue for subsea compression. Power transmission and variable-speed control are viable for short distances but are challenged over long distances (greater than 100 km).