Aquifer recharge to assist in the management of produced CSG water

Santos is producing natural gas and expanding its CSG operations in the Surat and Bowen Basins, Queensland for the Gladstone Liquefied Natural Gas (GLNG) project. During the project, it has been estimated that a total of ∼340 GL of associated water could be produced from gas extraction in three CSG fields. Beneficial re-use of this water is a high priority and one option involves treating the water and re-injecting it into the water supply aquifers in the Great Artesian Basin. In the past 100 years, groundwater pressures in the Gubberamunda Sandstone aquifer, Roma’s main town water supply, have declined more than 80 m and groundwater demand for the town water supply is now more than 5 ML/day. This demand, coupled with forecast droughts in modelled climate change scenarios, provides an impetus for the beneficial re-use of treated produced water. To assess the feasibility of the aquifer for managed aquifer recharge (MAR), a risk-based framework consistent with the Australian Guidelines for Water Recycling: Managed Aquifer Recharge was applied. A series of assessment stages designed to protect human health and the environment were undertaken, each allowing a decision point for investment. To date, a MAR well-field has been developed and numerous hydraulic tests have been undertaken along with laboratory/desktop evaluation of the geochemical compatibility of the injected water with the water and sediment of the target aquifer. An injection trial in Q4 2011 will evaluate the aquifer storage potential and confirm numerical/laboratory studies related to hydraulics and water quality compatibility.