Coal Seam Gas
Queensland’s coal seam gas (CSG) industry has grown rapidly over the past 15 years — the annual number of wells drilled increasing from 10 in the early 1990s to almost 600 in 2010–11.
The CSG industry has defied the recent global economic downturn with both exploration and development activity remaining strong. It continues to be at the forefront of Queensland’s petroleum industry.
The Queensland Government is supporting the growth of the petroleum industry by making available geoscientific information and company exploration data, and coordinating approvals for major petroleum projects.
In the past five years there has been a growing interest in using Queensland’s CSG resources to produce liquefied natural gas (LNG) for export, taking advantage of increasing global demand for gas. Three export LNG projects based on Queensland coal seam gas resources are under construction on Curtis Island near Gladstone with first cargoes expected in late 2014.
A further five proposals to develop export LNG projects are under consideration. If all current projects and proposals are developed to full capacity, this would represent a potential LNG export market for the state of more than 50 million tonnes per annum. Current infrastructure consists of more than 4000 kilometres of gas transmission pipelines. Additional pipelines to markets interstate and for supply of gas to the Gladstone LNG plants are planned or under construction.
Many Queensland basins are highly prospective for CSG and production in the Bowen (Permian coal measures) and Surat (Jurassic Walloon Coal Measures) basins represents more than 79% of the total gas produced in the state (Figure 1). As at 30 June 2011, proved and probable (2P) reserves reachedincreased to 234 PJ from 212 PJ in 2009–10 (Figure 3). Productionfrom these sources is expected to supply an increasing 33 001 petajoules (PJ) (Figure 2, Table 1). In 2010–11, production proportion of the Queensland and other eastern Australian markets.
The Permian to Triassic Bowen Basin is the birthplace of the CSG industry in Queensland. The first commercial production commenced from the Dawson River CSG area near Moura in 1996 and later from the Fairview CSG area near Injune in 1998. Currently, commercial production occurs in the central and southern parts of the basin near Moranbah, Injune, Moura and Wandoan. The Permian coal measures are the main targets.
CSG produced at Moranbah is sourced from the Goonyella Middle (GM) and P seams of the Moranbah Coal Measures. The coal at Moranbah has a rank greater than 1.1% Rv with vitrinite contents of the order of 60%. Future production is likely from the Goonyella Middle Lower (GML) seam while the overlying Fort Cooper and Rangal Coal Measures have potential.
Coal permeability in the Moranbah area is relatively low with production enhanced by in-seam drilling. Development has concentrated on seams at around the 300 metre level to avoid the loss of permeability that generally comes with increasing depth. As the Moranbah area is located in a hinge zone, with its associated faulting, areas of increased permeability are expected.
At Moura, CSG is produced from the Permian Baralaba Coal Measures. Coal ranks around the Moura area, along strike, have a range from 0.7% Rv at Theodore to around 2.1% Rv at Baralaba and about 1% Rv in the Moura area. Exploration and development is concentrated on seams around 300m in depth. Permeabilities are less than 10 mD in the Moura area. To cope with these low permeabilities, in-seam drilling has been undertaken to enhance production.
East of Wandoan at Scotia and Peat, gas is sourced from the Baralaba Coal Measures. Coal rank around Peat and Scotia is of the order 0.55 to 0.7% Rv with about 60% vitrinite content. The Peat and Scotia fields are located on the Burunga Anticline and contain structurally trapped free gas. Gas is produced from around 700 to 800 m depth where permeability is enhanced by the anticlinal structure. Below 900 m, the seams are considered sub-economic, where permeability is lower.