Management of CSG produced water

Leader

Challenge

Coal seam gas (CSG) has emerged as an important source of energy in many countries. CSG is essentially methane gas produced in coal seams at about 1,000 m depth, where it is trapped in fractures and on the surface of the coal. CSG production is commonly accompanied by the undesired co-extraction of a large volume of water to the surface. This water is known as CSG produced water is rich in sodium, bicarbonate, and chloride in Australia. This water is usually saline and sodic and must be treated prior to environmental discharge or beneficial use. The volume of produced water associated with CSG production for some basins is enormous. For example, the annual generation of CSG produced water from Southern Queensland alone is expected to be 175 GL/year, spanning until 2060 to result in an accumulative volume of 5,100 GL. Therefore, cost-effective and sustainable management of this large volume of produced water is of paramount importance to the CSG industry around the world.

Investigation

Develop a holistic approach to the management and beneficial utilisation of CSG water as well as its mineral content. Develop a low maintenance membrane distillation and multi effect distillation system using on-site low grade heat to increase water recovery. Evaluate the production of sodium hydroxide from the supersaturated concentrate using a chlor-alkali membrane electrolysis process.

Outcomes

The treatment train developed in this study consists of ultrafiltration (UF), reverse osmosis (RO), multi-effect distillation (MED), membrane distillation (MD), and membrane electrolysis. Extensive laboratory and pilot scale experiments were conducted to evaluate and optimise the performance of the proposed treatment train. Pilot scale evaluation at Gloucester, New South Wales, demonstrated that UF/RO/MED and UF/RO/MD are capable of recovering 98% and 95% of CSG produced water as high quality RO permeate and distillate respectively. Experiments also showed that CSG brine rich in NaHC03 can be used as the feed stock for the production of NaOH. The current efficiency when using CSG brine as the feed stock is lower than when the feed stock was a NaCl solution. However, the salinity reduction efficiency of CSG brine was significantly higher than that of a NaCl solution. In other words, membrane electrolysis can be deployed for the desalting process and production of commercial grade NaOH from CSG RO brine.

A new pre-seeding technique to control scaling was developed. This innovative technique is more effective than anti-scaling addition and allows for stable MED operation at 90% water recovery from CSG RO brine, corresponding to the overall water recovery values of the UF/RO/MED treatment train of 98%.

Future Direction

The results have contributed to AGL’s CSG water management pan. In July 2014, AGL announced on the Australian Stock Exchange that “will invest in a desalination plant to remove salt from produced water that is released during coal seam gas production in Gloucester”.

Partners

Nghiem partners


 

Total Value: $1,610,999 (cash and in-kind contributions)

Principal Investigator: Professor Long Nghiem

Title: Extraction of water and minerals from coal seam gas produced water for beneficial use

Length: 31 months

Personnel: 18 collaborators contributing 5.9 FTE

Related Project: Reverse osmosis brine management by membrane distillation crystallisation

Further Information

FR4 UOW Nghiem (CSG) Summary Poster

Project Summary Poster – CSG water

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