Timor Sea LNG Project
The Timor Sea LNG Project involves the following major components:

• Natural gas supply pipeline from the NT/P68 gasfield expected to supply the project with dry gas following stripping of liquids at infield production facilities
• 3 Mtpa LNG production module constructed on a self elevating steel barge.
• A single LNG tank with 170,000m³ storage capacity constructed on a concrete base to be sited in a water depth of ~14 metres on Tassie Shoal
• A separate Accommodation and Control Platform (ACP) connected by bridge links to the production module and storage tank
• Jetty for loading LNG into export tankers, or alternatively a ‘HiLoad’ single point mooring loading system east of the shoal
• Seawater cooling return system for the LNG production process

A 3D CAD image of the LNG and methanol (TSMP) facilities as they may appear on the shoal is shown below:

LNG PRODUCTION PLANT
MEO initially had a preference for a nitrogen expander cycle process for liquefaction, but as this is not used in any base-load LNG plants, the more efficient and commercially accepted Air Products & Chemicals Inc (APCI) mixed refrigerant process was adopted instead.  

APCI is a major manufacturer of industrial gases, cryogenic equipment and also licences cryogenic processes including LNG processes.  APCI’s propane pre-cooled mixed refrigerant process accounts for a very significant proportion of the world’s base load LNG production capacity.  Train capacities of up to 5 million tonnes per year (Mt/y) are operating, and trains of up to 8 Mt/y using the AP-X^TM variant are under construction.  A critical piece of equipment designed and manufactured by APCI is the main cryogenic heat exchanger (MCHE) which is a complex heat exchanger with thousands of spiral-wound aluminium tubes within a stainless steel shell.  The efficiency of the heat exchange process, equipment and the gas turbines which power the refrigeration process are critical for this energy-intensive liquefaction process.

The basic steps in a converting well-head gas to LNG are as follows:

As in all LNG processes, acid gases (mainly carbon dioxide), water and any traces of mercury are removed, the gas stream is pre-cooled and the heavy hydrocarbons are removed.  The gas is then liquefied in a further series of heat exchangers.  The APCI dual mixed refrigerant (DMR) process is used to avoid use of propane refrigerant for pre-cooling.  This uses a second mixed refrigerant comprising mainly ethane and butane which disperse more rapidly than propane (which has a density similar to air) in the unlikely event of a liquid refrigerant leak.  The DMR process is also compact and made more so by the use of special compact heat exchangers for condensing refrigerant flows and by electric motor driven compressors.  Electric drives also give high reliability and allow the possibility of combined cycle power generation, improving efficiency and reducing emissions.  Power generation by aero-derivative gas turbines also adds efficiency and reduces maintenance downtime and emissions.

Apart from power generation, the utilities plant includes steam and nitrogen generation, fresh water production from seawater by use of waste heat and fire protection systems,  The topsides will weigh approximately 15,000 tonnes.  

The self-installing (jack-up) substructure for the TSLNGP will follow the example of ConocoPhillips’ Hang Tuah compression platform offshore Indonesia and Origin’s Yolla platform.  It is essentially a barge built in a shipyard with jack-up legs providing a stable and clear platform on which the LNG facilities are built before tow-out.  This approach enables the facility to be tested and pre-commissioned before leaving the construction site, avoiding the need for heavy lifts of modules offshore and minimising costly delays in startup.

 


Environmental approval for the LNG plant on Tassie Shoal was received from the Australian Commonwealth Government on May 5, 2004.  The company is currently seeking expressions of interest for gas supply and equity participation in the LNG project.

LNG TANK DESIGN
Timor Sea LNG Project aims to construct a single LNG production module and a single LNG tank.  The tank would be a conventional 9% nickel steel primary LNG containment tank integrated within a concrete gravity structure (CGS) incorporating the secondary containment and a caisson base.  It will be designed for dry-build construction in a casting basin.  A second LNG tank and LNG production module could be installed several years later given an adequate gas resource.  

The 3D CAD image and design drawing below show the tank on its CGS which acts both as a transport barge and then a foundation when ballasted with seawater on the shoal.

LNG LOADOUT FACILITY
A single point mooring approach may also be possible for LNG loadout instead of a jetty and tugs.  The HiLoad system, a proprietary technology by Torp from Norway is the basis for this concept which has been under study.  It entails subsea cryogenic pipelines, a mooring buoy with LNG and gas swivels, cryogenic flexible hoses and the HiLoad semi-submersible docking device.  The HiLoad can manoeuvre by thrusters and attach itself to standard LNG carriers even under high wave conditions and then connect its loading arms to the ship’s manifold.  Most components have received certification and are anticipated to have commercial acceptance within a year.



For a computer-generated impression of a helicopter fly-in approach to the future LNG plant and other facilities on Tassie Shoal, click here