Coal Seam Gas Water - River Discharge: Context Matters

Abstract

Abstract Coal Seam gas (CSG) is a rapidly growing industry in Queensland, Australia. Water is produced as a by-product of the CSG production process, with the management of this associated water (called CSG water) widely accepted as one of the industry's main challenges. The Australia Pacific Liquefied Natural Gas (LNG) project is a coal seam gas (CSG) to liquefied natural gas (LNG) joint venture between Origin, ConocoPhillips and Sinopec Group. The Australia Pacific LNG project proposes to supply CSG from the Walloons gas fields in south central Queensland to a LNG plant located on Curtis Island, off the coast of Gladstone, on the central Queensland coast. Origin is the upstream operator of the Australia Pacific LNG project (the Project). In the Walloons coal seams, CSG water keeps natural gas adsorbed as a thin film on the surface of the coal. The pressure of the surrounding body of CSG water allows the gas to be retained within the seam by adsorption to the surface of coal particles. Hence to extract gas the water pressure needs to be reduced by transferring the water to the surface. Water from CSG wells extracted to enable gas production is variable in quantity, difficult to predict and influences gas production rates. Variability in water production can be due to the location of the well, communication with other wells, decline in pressure during well life and permeability of the coal seam. The quality of the CSG water can vary from well to well and more noticeably across the project area, but it consistently contains elevated quantities of salts. Appropriate management of CSG water is required to mitigate environmental risks associated with untreated CSG water. Uses for such large and difficult-to-predict quantities of both treated and untreated water in theWalloons gas fields region are limited. As such, it is acknowledged that the treatment, use and disposal of CSG water present a challenge for the Project and the CSG industry in general. This paper will use the Talinga development area, established in 2008 and located southwest of Chinchilla in Queensland as a case study in water management adopted by Australia Pacific LNG. In particular, this paper focuses on the discharge of treated CSG water to surface watercourses (creeks/rivers) - one of a suite of water management options used by the Project. This paper explores the regulatory framework governing this aspect of water management and Origin's approach to ensuring the environmental values of receiving waters are preserved. At time of writing, the gas production from the Talinga field has been operated under an Environmental Authority (EA) with provision for an initial 18-month continuous discharge to the Condamine River of 20 ML/d as the preliminary water management option underpinning a broader management strategy. The broader strategy includes transitioning to a managed discharge flow regime that mimics the natural flows of the River.