Offshore Transfer, Re-Gasification and Salt Dome Storage of LNG
Authors: de Baan J. , Krekel M.H. , Leeuwenburgh R. , McCall M.M. 
Published: October 2008

The paper describes a design family for 'ship to ship and 'ship to shore' transfer systems for LNG. The common design philosophy is explained and each configuration is described briefly. Auxiliary systems and equipment are discussed as are operational procedures.

A case study is presented for a near shore LNG terminal, comprising a marine transfer system in combination with a regasification plant and a salt dome storage cavern. The regasification plant and the salt dome storage cavern are treated extensively.

The systems described will greatly advance the implementation of offshore terminals for LNG. Although new, all of the components used are proven and have been applied in LNG terminals and offshore loading systems longtime.

Introduction

LNG is the fastest growing hydrocarbon fuel; while gas as a primary fuel source is forecast to grow at 3% in the coming wo decades, LNG as a subset is forecast to grow at double that rate over the same period.[1] The development of LNG has been encouraged by the enormous amount of stranded gas, a reduction in gas flaring, an ongoing 'greening' of the energy mix and several price spikes in natural gas prices. These many factors have stimulated growth of LNG production but also introduce 'commoditization' of LNG because of the substantial new sources of supply.

The U.S. is currently by far the world's largest gas market. Of the current supply 85% is produced within the US, and 15% is imported; 98% from Canada and only 2% in the form of LNG. Whereas U.S. demand is expected to grow with 2% per annum, the current U.S. gas production shows an increasing intrinsic decline rate and more newly discovered gas is needed each year to keep up with demand. No excess capacity exists at the wellhead. Current demand for winter heat is greater than storage and production.[2] In order to stabilize price, there is a need for increased storage capacity. With current producers struggling to maintain production, LNG is likely to capture a portion of the foreseen growth.

Community concerns, congested ports, security and cost considerations are seen to slow the development of significant increases in capacities to receive LNG in the U.S. and Europe. This paper will describe an offshore alternative to moor, unload, store and distribute gas sourced as LNG that has the potential to be faster to build, less expensive, much more secure, and more acceptable to the community than conventional alternatives.

Besides the liquefaction plants and shipping, a few key elements in the gas chain between production and delivery are the loading and offloading operations of the LNG ships, the re-gasification and the temporary storage of LNG and/or gas.

For the loading of LNG into the tankers and for the offloading thereof, terminals are required. The terminal at the loading side is normally close to the liquefaction plant. Traditionally on the offloading end, the terminal is situated near a temporary storage facility and re-gasification plant. After the LNG has been re-gasified, it is brought into the pipeline network to distribute it to the consumers.