The Q-Max more than doubles the cargo capacity of the original LNG carriers. Click to enlarge. Source: ExxonMobil

The large LNG ship technologies, developed in conjunction with joint venture partner Qatar Petroleum, include a number of industry breakthroughs and significant enhancements, including increased ship size, onboard reliquefaction units, slow-speed diesel engines, twin propellers and rudders, largest ship-board LNG tanks ever built, the latest in hull antifouling protection and improved fire-protection systems. The end result of these new generation ships is a 20-30% reduction in transportation cost.

For more than 30 years the size of LNG ships remained essentially unchanged,with capacity  of about 140,000 cubic meters. In 2007, Qatar Petroleum and ExxonMobil launched the Q-Flex carriers, smaller versions of the Q-Max, with capacity between 210,000 m³ and 216,000 m³. Qatar Petroleum and ExxonMobil’s ship operators, hydrodynamicists, naval architects and structural engineers worked closely to develop and test the larger Q-Max cargo tank designs. Comprehensive evaluation of cargo sloshing was performed to prove that the larger systems were feasible and reliable.

The resulting Q-Max carriers are longer than three football fields, rise twenty stories from keel to masthead and are equipped with the largest membrane containment tanks ever built. With a total capacity of up to 266,000 cubic meters, each ship carries enough natural gas to meet the energy needs of 70,000 US homes for one year.

Qatar Petroleum, with ExxonMobil, led a major technical effort to enable this significant enhancement in the LNG shipping industry. Shipping is a critical link in the LNG value chain that extends from Qatar’s North Field, the largest non-associated gas field in the world with recoverable resources of more than 900 trillion cubic feet, to homes in Asia, Europe, and the Americas. With our innovative technology, we have effectively transformed the LNG business and opened up more of the world for Qatar LNG.

—Faisal Al Suwaidi, Qatargas Chief Executive Officer

The Q-Max carriers are equipped with the largest membrane containment tanks ever built. One of the five ship-board LNG membrane containment tanks is pictured here. Click to enlarge.

Qatar Petroleum and ExxonMobil are shareholders in a Qatar joint venture, Qatargas, that will charter the Mozah and five other Q-Max carriers to supply LNG from new liquefaction trains in Qatar.

Three of the ships will be built at Samsung Heavy Industries (SHI), with a cargo capacity of 266,000 cubic metres, and the other three at Daewoo Shipbuilding and Marine Engineering (DSME) with a cargo capacity of 263,000 cubic meters.

In addition to increasing the size of the ship, a major initiative was undertaken to design, test and implement the on-board reliquefaction plant that re-liquefies natural gas that is vaporized during transit, re-injecting it as liquid into the cargo tanks rather than using it as vaporized gas to power the tanker itself. This capability enables the delivery of nearly 100% of the cargo. This is particularly beneficial for the long-haul voyages from Qatar to Europe and the Americas.

The on-board reliquefaction facilities created an opportunity to shift from steam boilers and turbines used for propulsion by conventional LNG ships to efficient slow-speed diesel engines. The Q-Max ships are equipped with two diesel engines driving twin propellers and rudders. This leads to more energy-efficient, reliable and maneuverable ships, reducing fuel consumption by up to one-third.

In addition to pioneering the industry’s largest vessels to carry LNG to market, ExxonMobil in partnership with Qatar Petroleum is employing new technology in Qatar to build four of the largest LNG production facilities in the world and is participating in the development of LNG regasification terminal projects in Italy, UK and the US.

Resources

• The Outlook for LNG (ExxonMobil, APPEA Annual Conference)