Well well, doubts on drilling

Dr Luke Connell from the CSIRO’s Earth Science and Resource Engineering department is an expert on coal seam reservoirs.

He is researching the science of how gas is produced from the reservoir, how to characterise it, how much is there, how it flows and how you predict that gas behaviour.

Dr Connell said the horizontal drilling technique that Metgasco is planning to use in multiple wells in the Clarence-Moreton basin in the Northern Rivers is one of the industry standard techniques used for coal seam gas extraction.

“It’s good for coal seams that seem to be thinner reservoirs,” Dr Connell said. “The well follows the reservoir so it gives you more contact than a vertical well. There are a lot of factors that determine what the best technique is, sometimes its horizontal wells, other times vertical, and other times other techniques.”

In a story published on March 3 Metgasco’s David Johnson told The Echo that the method they use ensured that their drilling and subsequent activities had no contact with aquifers and their method ensured there was “no aquifer contamination”.

However Dr Connell’s comments seem to cast doubt on that certainty.

“With horizontal wells there is the potential for aquifer impacts. It all comes down to how the reservoir with the coal seam gas is targetted and how that interacts with aquifers. Usually the gas present is hydrologically separate from aquifers but it’s very site specific,” he said. “There are a range of things that determine the potential for CSG impacting on aquifers. There are regulations that have been developed to regulate the management of aquifer impacts and they place obligations on the company to monitor and assess potential impacts, although I’m not sure exactly what those regulations are in NSW.”

Dr Connell said the water produced by CSG extraction could, in some instances, have potential uses.

“It’s very site specific, case by case, and depends on ground water quality,” he said. “For regions with good ground water quality, it can be a benefit to have an additional water source. There have been regulations developed regarding produced water. Queensland’s done a lot of work looking at the management of produced water, they’ve just moved further along the scale of the industry (than NSW).

“If you have saline water produced there is potential for that water to have detrimental impacts. There is awareness of that issue and, again, I’m not sure how it’s managed in NSW. Disposal basins are one of the techniques that have been used, but there are others including water treatment and reverse osmosis. There is certainly a cost in treating the water. That cost relates to its quality, how much energy you have to put in to treat it.”