Waste water is an issue for CSG producers, with large volumes of water often produced from CSG wells. Producers and petroleum engineers are working to more effectively manage what should and can be done with the water. And how to make water production from these wells economically, socially and environmentally viable.
Salty volumes
The two main issues CSG producers face when it comes to the water produced from their wells are managing its volume and its salt content.
Ian Cameron is a Principal Water Engineer at Parsons Brinckerhoff and has worked on water management issues with a number of CSG producers in Queensland. Currently, he is working on stage two of Arrow Energy’s reverse osmosis project at Dalby. The company has also completed studies with Origin Energy as well as with the Queensland Department of Infrastructure and Planning, which looked at matching supply and demand for CSG water.
Mr Cameron says the amount of water produced from CSG wells varies widely but, in broad terms, Parsons Brinckerhoff studies have shown there to be something like over 20,000 mega litres (ML) in Queensland’s Surat Basin.
Today, he adds, this estimate could probably be multiplied by four or five as it was determined before the proposed liquefied natural gas (LNG) facilities in Gladstone were announced.
The problem with CSG water is that it is brackish, or partly salty, which makes dealing with it difficult because, in most cases, it has to be treated for reuse. Sea water typically has a ratio of 35,000 total dissolved solids (TDS) – the combined content of all inorganic and organic substances contained in a liquid – either milligrams per litre or parts per million. The best CSG water is in the realm of 2,500 TDS but, depending on the area it comes from, its salt ratio can be as high as 8,000-12,000 TDS.
Water management today and tomorrow
Currently, CSG producers have the following water management options: underground injection, storage and evaporation in evaporation ponds, surface discharge as well as beneficial and commercial uses.
Producers predominantly use evaporation ponds; however, these ponds can leave a salty crust that must be disposed of.
With growing environmental consciousness and the desire to reduce their environmental impact, CSG producers are investigating how to use the water produced from their wells for commercial and beneficial purposes. Mr Cameron explains that there are currently a few options open for CSG producers in dealing with their waste water, including its use by power stations, for coal washing, for agriculture or to be treated for town use.
All these options are accompanied by different costs, as well as technical and logistical challenges. Coal miners can use the water basically as is for coal washing but the water often has to be piped to the mine, adding infrastructure and pumping costs. Power stations can also use the water but it must first be desalinated to very high levels. This is also the case if the water is used by towns.
Mr Cameron says there are a number of Queensland towns currently looking to desalinate CSG waste water, including Dalby, Chinchilla and Miles.
Queensland Gas Company is negotiating with the Queensland Government regarding a water pipeline proposal from its Queensland acreage to Toowoomba to be used in drought-affected towns and communities most in need of water. In July, the Queensland Government won a $5 million grant for a feasibility study into the use of water produced from CSG extraction.
Arrow has said it will transport water from its CSG wells through a new pipeline to a preliminary treatment plant and reverse osmosis plant in Dalby. The company’s Surat Basin operations currently produce around 13 ML per day of CSG water but this figure is expected to peak at over 150 ML per day within the next few years.
Still, the costs associated with these beneficial uses of CSG waste water can be high.
Mr Cameron says that if using reverse osmosis technology to desalinate the water, costs are typically up to $2,000 per ML. The price is increased if the water needs to be transported – that is, pumped through a pipeline.
Origin has built the first fully integrated CSG water treatment facility in Australia. It processes water onsite at its $20 million, 9 ML water treatment facility at its Spring Gully gas plant near Roma. The company is currently exploring commercial and beneficial uses for the water.
Mr Cameron says that ultimately, whether water treatment is viable at a certain site and for a certain producer depends on the user’s willingness to pay, the economics of what the parties involved are trying to do and what the water will be used for.
There is no single solution to managing waste water from CSG wells, he says.
“You might sell some to a town; you might sell some to a feed lot; you might evaporate some; you might pipe some to a coal mine; and you may reinject the rest back down into the coal seams,”? he says before posing the problem again as a challenge.
“There’s unlimited land in the Surat Basin. If you can get CSG water down to 1,000 TDS and a low sodium absorption ratio [the ratio of sodium compared to the combination of calcium and magnesium, or beneficial elements in the soil]; If you can get [adequately treated] water down to $350 per ML then I think there would be plenty of farmers who would be willing to pay to use it on crops.”?
The problem is the gap between delivering this affordable water and the current price of treating the water at $2,000 per ML.
“That’s the gap and that is the problem at the moment,”? says Mr Cameron. “How do you desalinate it more cheaply than reverse osmosis?”?
He believes there are great economic opportunities for reverse osmosis out there but there doesn’t seem to be any economic solutions in the short term. And while there are some alternative technologies, not many have been successful at a large scale.
Although it is not widely used and many producers claim that it is too expensive, Mr Cameron believes reinjection offers a viable solution.
“The salt came from 600 metres underground and that is probably where it should end up after the gas has been taken out. I think in the longer term that’s probably what will happen.
“There may be geological reasons why they can’t do it but environmentally, to put it back where it came from is probably a good solution.”?