Australia’s ramping up energy production and liquefied natural gas exports to be a global gas superpower by 2017. Many Coal Seam Gas developers are working diligently to bring this new resource to market, which requires a reliable extraction and management of billions of gallons of coal seam water.

By: Beccy Philby, CH2M HILL Senior Project Manager and Andrew Hodgkinson, CH2M HILL Senior Principal Technologist

A report published recently by Morgan Stanley reveals that Australia is poised to be the biggest exporter of liquefied natural gas (LNG) in the world by 2017.

Many Coal Seam Gas (CSG) developers are working hard to bring this new resource to market via new LNG export terminals in Gladstone. These terminals, plus the vast array of connecting infrastructure currently under construction in Queensland, will depend ultimately upon reliable extraction and management of many hundreds of billions of gallons of coal seam water. This water is the by-product of CSG extraction, and optimum management of it is a key enabler for unconstrained gas production.

Typically coal seam water is treated by a series of reverse osmosis (RO) plants to enable beneficial use, and the resulting brine is stored until its final management is determined. Reducing brine volume through further treatment can significantly reduce the cost and legacy risks associated with long term brine storage. Throughout the years, CH2M HILL has helped many clients develop systems similar to the energy intensive forced evaporation based systems currently preferred for CSG brine concentration. However, in the last few years, we have also begun helping clients in many locations develop more energy efficient, membrane based methods.

The challenge to brine volume minimization following RO pre-concentration of coal seam water is the risk of silica scaling. In Queensland, coal seam water from the prevailing hydrogeology means that the initial RO treatment step often produces a concentrate stream close to silica saturation (typically about 200 mg/L as SiO2). This limits the maximum attainable brine concentration via RO sometimes to as low as 25,000 mg/L total dissolved solids (TDS).

By reducing the silica concentration, without limiting the RO performance, a second RO process step can then be used to achieve a much higher TDS, approaching the salinity/pressure limits of available RO equipment. This permits a significant brine volume reduction avoiding the heavy energy use associated with evaporative methods.

CH2M HILL has explored this type of process in several instances, most recently for an Australian CSG client. The key technical challenge was the method of silica removal, for which our extensive experience in cold and warm lime softening, augmented with magnesium for silica removal, has been a vital capability.

Beccy Philby is a senior project manager at CH2M HILL and currently leads a suite of water and environmental management projects associated with upstream oil and gas activities. As account manager for a major CSG client, she coordinates CH2M HILL’s full-service delivery to help clients maintain timely and cost effective environmental solutions and engineering designs.

 

Andrew Hodgkinson is a senior principal technologist at CH2M HILL, working for the Australia/New Zealand region. In addition to his long standing duty as Technical Director of the Gippsland Water Factory (now a post handover support role), he is assisting with several industrial water projects and leads CH2M HILL’s developing Industrial and Urban Ecology program.