a sea change for LNG carriers

This article originally appeared in the Lamp, 2007 — Number 3

Qatar Petroleum and ExxonMobil are launching a new generation of larger and more efficient ships that can deliver liquefied natural gas (LNG) to the world’s major energy markets. The innovative ships — in two sizes — carry up to 80 percent more cargo than conventional LNG carriers. The fleet will include 45 ships, of which 21 are under construction, and the first four will begin service this fall.

The size of LNG ships has been virtually unchanged for more than 30 years. In 2001, however, joint venture partners Qatar Petroleum and ExxonMobil wanted to expand beyond the primarily Asian market for Qatar’s liquefied natural gas, and that meant finding a better way to deliver LNG to more distant ports. As a result, ExxonMobil initiated a study to examine the feasibility of larger ships that have since become the standard for all of Qatar’s expansion plans.

"Shipping accounts for about one-third of the cost of LNG," says Tony Urbanelli, senior project manager for LNG transportation. “So to cost effectively reach more distant markets, we needed a new class of carrier that was more efficient than anything available at the time.”

Simply increasing the size of the ship was not enough. To obtain the efficiency needed, teams of experts studied fuel and propulsion systems, power plants and hull configurations. The breakthrough came by moving onshore LNG processing technology onto a ship.

"Cooling natural gas to minus 260 degrees Fahrenheit (minus 163 degrees Celsius) turns it into a clear liquid that occupies only a small fraction of the space required to transport natural gas," Urbanelli explains. "But in the course of a long sea voyage, some of that liquid expands back into gas, which conventional LNG carriers burn in boilers to help power the ship."

During the trip between Qatar and the U.S. Gulf Coast, up to 5 percent of the cargo would be consumed as fuel.

"To deal with the liquid that expands back to natural gas, we decided instead to install the equipment necessary to reliquify the gas onboard and re-inject the liquid back into the ship’s cargo tanks," Urbanelli says. "Since we no longer needed boilers to dispose of the gas as fuel, other options for powering the ships could be considered, which means they deliver nearly 100 percent of their valuable cargo to the point of sale."

One solution, two sizes and 45 ships
Over the course of two years, the design team settled on two similar ship platforms they called the Q-Flex (Q for Qatar, and Flex for the flexibility to access most LNG ports) and the slightly larger Q-Max (Max for the largest ship that can use the Qatar LNG terminal).

"The Q-Flex carries 50 percent more LNG than the average carrier operating today while the Q-Max transports 80 percent more," says Matt Greer, manager, LNG ships and marine systems. "The Q-Max can deliver the equivalent of 5.5 billion cubic feet of natural gas. That's enough to meet the energy needs of 70,000 U.S. homes for one year."

Three Korean shipyards are building 21 of the big ships now. A total of 45 Q-Flex and Q-Max LNG carriers have been contracted for delivery between 2007 and 2010. Each of the yards was expanded to handle the work.

"One ship takes about three years to complete," says Bill Bray, LNG ship design and nautical services supervisor. "ExxonMobil personnel are part of the team responsible for ensuring the ships meet the requirements of all of the Qatar joint ventures. The ships will be leased by the joint ventures for a period of at least 25 years."

"This project is a huge step forward in reducing the cost of transporting LNG," says Andy Richardson, an ExxonMobil secondee leading the Qatar construction oversight effort. "That saves money for the joint venture partners, but it also saves energy and reduces emissions. The Q-Max consumes about 40 percent less energy per cargo-ton mile compared to a conventional vessel. That is a huge boost in efficiency, especially for an increasingly competitive industry like LNG."

Completing the chain
Shipping is a critical link in the LNG value chain that extends from the gas wells of Qatar’s North Field to homes in Asia, Europe and the Americas. While there are many operators in the global LNG business, the Qatar Petroleum and ExxonMobil team has become an industry leader, and the development of the Q-Flex and Q-Max ships is another example of the close working relationship between the companies.

"This is one of the largest commercial ship development programs ever," Urbanelli adds. "I think that for the many team members who have worked on this project for a number of years, it is the most significant event in our professional lives. It's hard to imagine another project that could make such a substantial change in the shipping industry."