Only a few short years ago, developments in coal seam gas (CSG) production on the current scale were unthinkable to most.

Common thinking was that CSG fields would typically last only a few years, which encouraged the design of small capacity plants at low cost and little thought was given to long-term operation.

Development of CSG processing

The original process designs for the dehydration and processing of CSG in New South Wales and Queensland began around 2000.

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Operation of the CSG processing plants soon showed that the amount of water, coal fines and other contaminants that carried over into the gas stream could be handled with subtle but important changes to the design of equipment packages that were being used for conventional gas dehydration.

Years later, the initial small capacity plants are still in use and many plants have been added to new and surrounding CSG fields. The focus of plant design and construction has switched to longer-term issues, with operation and maintenance access being given higher priority, along with minimising maintenance in the remote areas.

The original process designs for the dehydration and processing of CSG have since developed into reliable packages being used by most of the CSG producers to produce pipeline quality dry gas.

Experience has taught CSG producers that all CSG wells must first be de-watered and the large volumes of saline water must then be treated and disposed of. In addition, extensive gas compression is required to collect the low pressure gas and boost it to high export pipeline pressures. CSG must also be dehydrated in order to reduce moisture (water) to meet pipeline sales gas specifications.

Dehydration and regeneration plants

Process Group has designed and built the majority of the tri-ethylene glycol (TEG) gas dehydration and regeneration plants used for CSG in Australia.

Over the last ten years, these designs have evolved into skid-mounted packages that are trucked to sites without special transport or escorts. Designs have evolved to minimise the amount of electrical and piping connections and onsite man-hours required to install each package.

Learning from both the design and fabrication side, as well as through feedback from the field, has allowed design decisions and equipment selection to reach an overall structure/outline design that is reliable, functional and suits the operating environment.

The future of CSG

The volume of gas produced in Australia has increased dramatically in recent years and will continue to expand more rapidly in coming years to meet domestic gas consumption and potential.

Development plans are leaning towards the continuation of the highly modular and portable design basis – less than 100 million cubic feet per day (MMcf/d) of gas dehydration capacity – although some are considering having fewer larger plants (200 MMcf/d capacity).

The size and number of plants to be built is increasing, with at least one LNG facility at Gladstone in Central Queensland due to begin design and construction in 2010, and other schemes are likely to follow.

One constant feature is that the ongoing growth of the CSG industry will continue to drive innovation and evolution of targeted solutions to create more reliable and economical facilities.