Water Journal : Water Journal November 2012-1
water NOVEMBER 2012 47 special report Professor Simmons also agrees the initial focus must be on accruing baseline data to assess before and after impacts on water levels, chemistry and recharge rates. “It requires a real knowledge project that quantifies potential impacts on water resources using leading practice groundwater modelling and risk assessment approaches,” he said. Queensland CSG Groundwater Report An integrated water monitoring strategy is among the key recommendations in the QWC’s Surat report. Under its proposal, an integrated network of nearly 500 monitoring points at 142 geographic sites is needed to collect data on water levels and basic water quality. This includes an additional 392 monitoring points to be provided by CSG companies in several aquifers and at various depths. The monitoring data will enable progressive refinement of the regional groundwater flow model. “The regional groundwater flow model allows a cumulative approach to assessing the combined impacts of the CSG developments in the area,” said Randall Cox, General Manager for CSG Water at the QWC. “The aim is to better understand the way groundwater flows and the interconnection between the aquifers.” A science-driven monitoring system that is sufficiently predictive of what is happening can act as an early warning system to ensure that any initial impacts are not significant. Predicted Decline in Water Bore Levels The QWC draft report identifies about 21,000 registered water bores within the Surat area that are used for a variety of purposes, including grazing, irrigation, industrial and urban consumption. As a result of CSG mining, QWC expects 528 of these will experience a decline in the water level of more than the trigger threshold. The trigger level is expected to be reached at 85 registered water bores within three years. Under the Queensland legislative framework, the threshold is a five-metre water level decline in consolidated aquifers, such as sandstone, and two metres for unconsolidated aquifers, such as sands. By law, petroleum tenure holders must ‘make good’ affected private bore supplies though measures that might include altering the bore or establishing a replacement water supply. The draft report proposes rules to decide which company is responsible if more than one contributes to the impact. Tenure holders will also have to explore potential mitigation options at five of the 71 spring complexes in the Surat Basin, where impacts on water levels in the source aquifers are expected to fall by more than 20 centimetres. Treating the Produced Water Removing groundwater is one issue – what to do with it once it has been removed is another. The water is often too salty or brackish for normal use and the preference is not to leave it in large retaining ponds to evaporate. This means it has to be treated. Australian Pacific LNG (APLNG) is operator of one of the largest CSG operations in Queensland and project partner Origin has been involved in CSG for nearly 15 years. Origin’s Groundwater Manager, Andrew Moser, said produced water from APLNG’s mining goes to the highest value user, usually the mining operation itself or for agriculture. Brackish water is treated at two reverse osmosis desalination plants to drinking water standard. The operators are also trialling reinjection of the treated water back into suitable aquifers, the preferred option of the Queensland Government. “We started injection trials at Spring Gully in April and have been injecting 2ML to 2.5ML of water back into the aquifer each day,” Mr Moser said. “That’s a fantastic result because the engineering behind it has been far more complex than we envisaged. “We have to degas and deoxygenate the water and treat it to make sure we don’t have any bacterial growth. The quality of the water which comes out of the reverse osmosis plant is about the same as that in the aquifer.” Injection trials at two other locations are planned before the end of the year and a fourth will start next year. “The purpose is to determine the technical and economic feasibility of injection and at this point it’s looking far more favourable than what we expected,” Mr Moser said. “We’re pretty happy with the way it’s going.” Deep Well Fracking Sparks Controversy There are many different geological layers in the Great Artesian Basin, including porous sandstone through which water can flow. Above and below these main aquifers are The Queensland Government estimates that about 8 per cent of CSG wells in the state have been fracked.
Water Journal December 2012
Water Journal September 2012-1