The first part of this article in the February issue of Sea Breezes considered key trends in the evolution of oceangoing LNG ships from the first commercial cargo, in 1964, to the present day, noting in particular the growth in cargo capacity from 27,400m3 in the case of the Methane Princess to today’s standard of about 175,000m3. In recent years, the LNG industry has faced several significant technical challenges related to the floating production and re-gasifi cation of LNG, and the exploitation of gas reserves in Arctic regions.
During the 1970s much work was expended into assessing the feasibility of producing and exporting natural gas from the hydrocarbon-rich islands and offshore regions in the Canadian and Alaskan Arctic. One consideration for transporting the gas was to use submarines which, naturally, would be unaffected by surface ice and weather conditions. Moreover, prevailing water depths of over 350 metres would enable submarines to maintain cruising depth and speed over practically the entire length of the proposed routes. For this purpose, General Dynamics developed a series of designs of Arctic LNG submarines of 27~140,000m3. As well as nuclear propulsion, these designs featured a traditional steam-powered system using cargo boil-off gas (BOG) and, when submerged, re-circulated exhaust gas mixed with oxygen from a liquid oxygen tank. The idea of using submarines also came to the fore in studies of transporting natural gas in compressed form, but neither LNG nor CNG prototypes were ever built.
As an alternative to submarines, the Arctic Pilot Project conceived in 1976 by Petro-Canada and partners envisioned the use of two 140,000m3 ice-breaking LNG carriers each making about 15 round trips per year from a shipping terminal on the south coast of Melville Island located on the eastern side of Sabine Peninsula. The routing would take the ships in an easterly direction via Parry Channel, then across Baffin Bay and through Davies Strait to a receiving facility in St. John, New Brunswick. Dubbed the “Melville Island Monsters”, the ships were to be 372m long by 43m wide, and 11m draft, with three propeller shafts providing for 18.5 knots performance in open sea and a constant 3 knots through 2.1m thick first-year ice. Propulsion was to be electric, with six generators driven by six gas turbines, three capable of burning BOG and heavy fuel oil; the other trio just BOG.
Whilst the Arctic Pilot Project failed to make headway, the plans for the Melville Island monsters have, forty years later, many similarities to the ships being built for the Yamal LNG project in Siberia. In 2013, Daewoo Shipbuilding & Marine Engineering was chosen as the winning bidder to build fifteen 172,000m3 Arc-7 ice-class LNG ships for the project. With an enforced steel hull twenty-five percent thicker than equally-sized non ice-class ships, the Arc-7s are designed to pass continuously through ice up to 2.1 metres thick, and without the assistance of Russia’s nuclear icebreakers. The Russian Register Arc-7 standard is equivalent to an intermediate level between Polar Class 3 and Polar Class 4 of the international association of classification societies. The ships will be highly winterized enabling normal operation in -45 Celsius ambient temperature, with the equipment certified for work at -52 Celsius.
Starting at plateau output in 2020, and during each of the subsequent 25 years at least, the Yamal project will export 16.5 million tonnes of LNG. Shipments will be in a westbound direction from Sabetta port during winter and spring, and eastward in the other seasons when ice flows retreat sufficiently in the Northern Sea Route to enable Far Eastern markets to be served. Yamal’s main sponsor is Novatek with partners Total, and China National Petroleum Corporation; the Chinese being the key financiers. The first ship was launched in January 2016 and is due for delivery to Russian owner Sovcomflot in February 2017. It was to be named simply as SCF Yamal, but was eventually christened Christophe de Margerie in memory of the late President of Total who pushed the project forward despite western disapproval of the company’s backing of a major energy export project in Russia. On 20th October 2014, less than ten months after the final investment decision on the project, de Margerie was killed when his private jet collided with a snow plough when taking off from Moscow airport.
The Arc-7s are double-acting - designed to steam ahead in open water and thin ice, but turn around and proceed astern in heavy ice conditions. A key feature of the ships’ manoeuvrability in Yamal’s ice conditions are three 15 MW azimuth propulsion units – or azipods as manufacturers ABB has dubbed them – each consisting of a steerable pod containing an electric motor drive. The trio of pods will be powered by six Wartsila duel-fuel engines capable of handling the wide load variations that can occur when a ship passes through thick ice.
Another technologically challenge witnessed by the LNG industry lately has been the development of floating production & liquefaction units – known as FLNGs – as sponsors seek to exploit small or remote offshore gas reserves for which traditional land-based facilities are unsuited. Floating liquefaction is not a new concept. In fact, it predates the first ships. Prior to the converted Methane Pioneer (a 1945-built Liberty ship) that delivered 7 cargoes from the US Gulf to Canvey Island, and before the first commercial cargo from Algeria to the UK, Chicago Stock Yards’ original concept in the 1950s was FLNG. The barge, tethered to shore, was a relatively simple design as compared to the sophisticated vessels presently being planned where the civil and chemical engineering of the topsides account for a much greater share of the challenges, and costs, than the hull.
It’s doubtful those pioneering fellows at Chicago Stock Yards could have envisioned the scope of Shell’s Prelude FLNG – the first to be ordered in the modern era – which, at 488m (1,600 feet) long, 74m (240 feet) wide and 44m (143 feet) deep from the keel to the main deck will, along with its contents, weigh around 600,000 tonnes. By comparison, the oil tanker Seawise Giant (1979~2009), generally considered the largest ship ever built, had a loaded displacement of 657,019 tonnes. Shell refers to Prelude FLNG, which will operate in waters of 200~250 metres’ depth, as a floating facility rather than a ship, and, as such, it will be the world’s largest ever built when eventually completed, in early 2018 perhaps, which would be almost three years behind the original schedule.
The behemoth, designed for 50 years’ service at various locations, will be towed to the Prelude gas field, some 475 kilometres north-east of Broome, Western Australia, and moored there for 20~25 years before needing to dock for inspection and overhaul. Each of three Rolls-Royce azimuth 5.2MW thrusters for local manoeuvring are situated at the base of a trunk that links to a higher maintenance workshop area with cranage. The Prelude FLNG facility is being built by Samsung Heavy Industries to TGZ membrane design and will produce annually 5.3 million tonnes of petroleum liquids – including 3.6 million tonnes of LNG.
The delays with Prelude have meant that it will not be the first offshore FLNG unit to be built; that feat was achieved by Petronas’ PFLNG Satu, ordered after the Shell contract, and delivered by Daewoo in May 2016. Of GT membrane design, the PFLNG Satu has been deployed at the Kanowit gas field off Sarawak where it will produce 1.2 million tonnes LNG per annum.
Unfortunately, the advent of FLNG has coincided with deep and protracted declines in oil and gas prices, making new project development less economic. Shell has cancelled options it had at Samsung to order three more of the giant units that would have been used to exploit other offshore gas fields. Petronas has postponed delivery of its second unit - the PFLG Dua - which had its keel-laying ceremony at Daewoo in April 2016 and is now expected not to be commissioned until 2020 – two years later than originally planned. More positively, Italians ENI and partners BP seem about ready to order an FLNG unit at Daewoo to develop a project at Coral South off Mozambique with 3.3 million tonnes per year of LNG.
Owners of older conventional LNG ships; of which a dozen or more have changed hands over the past couple of years, have been studying the prospects of converting them to FLNG units. Golar LNG – which has already converted the 1970s built Golar Spirit and Golar Freeze to floating storage & regasification units, or FSRUs described in the next section, is involved in projects that would entail converting ships of similar vintage to FLNG units.