An overview of the coal seam gas developments in Queensland

Abstract

The demand for natural gas in Queensland, Australia has historically been supplied from conventional reservoirs. However, depletion in conventional sources has led producers to turn to extensive supplies in Queensland's coal resources. These coal seam gas (CSG) developments not only represent new supplies for the domestic market in eastern Australia, they are also the first time that CSG (aka coal bed methane or CBM) has been liquefied to serve the expanding world LNG market. In order to make this development occur, considerable infrastructure had to be installed, with field developments still on-going. This AUD$60 billion investment precipitated a major overhaul of state regulations to provide not only a safe and clean operating environment, but also to allay the concerns of certain stakeholders.The gas is primarily produced from thin high permeability coals in the Jurassic-age Walloon Coal Measures in the Surat Basin and from several relatively thick Permian-age coal seams in the Bowen Basin, of which the Baralaba Coal Measures and the Bandanna formation are the most important. There are numerous technical challenges with this production, such as fines production from the inter-burden clays, which can form a thick paste that is difficult to pump. Salt extraction by reverse osmosis, from associated water produced to depressurise the coal seams and enable the flow of gas, allows for the beneficial use of the water. Technical challenges also include mathematical modelling of the countercurrent two-phase flow (gas and water) in the well annuli because conventional models in simulators only handle co-current two-phase flow in the well-bores. Also, the subject of ongoing investigations is decommissioning of the large number of shallow wells over the next few decades in a safe and cost effective manner, with compressed bentonite being a promising option for well plugging.As with any major commercial development, in addition to the technical challenges there have been social challenges as well. These include interaction and coexistence of extensive surface operations with an established agricultural sector, interactions between gas M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPTproduction and ground water aquifers in water-stressed areas, and the cumulative social and economic impacts of 3 large projects on a rural area.Ultimately, the State of Queensland expects to produce more than 1,800 BCF/annum, of which about 1,400 BCF/annum will be exported as LNG. Depending on the demand and well productivity, up to 1,000 CSG wells may be drilled per year for the next thirty years. A review of CSG resources, development, and challenges is presented in this paper to provide context for a stream of research findings that are emerging on the Queensland CSG experience. M A N U S C R I P TA C C E P T E D ACCEPTED MANUSCRIPT construction and development phase to a production and operational phase it is timely to review how it occurred, the challenges overcome and the prospects for the future. The lessons learned and discussed...

Petroleum Plays of the Bowen and Surat basins

“…Most traps in the Showground and Precipice sandstones have formed as a result of drape over or onlap onto preexisting palaeo highs (Towler et al, 2016). Due to the dominance of fluvio-deltaic environments in the sequence, there should also be good potential for stratigraphic traps.…”

“…Due to the dominance of fluvio-deltaic environments in the sequence, there should also be good potential for stratigraphic traps. In the Denison Trough, traps are dominated by structural closures (Towler et al, 2016).…”

“…Lower permeability plays (e.g. Dawson River, Moranbah), are found in the northern Bowen Basin, and are generally targeted by using surface to inseam drilling techniquies (Towler et al, 2016).…”

Developing synthetic reservoir type curve model for use in evaluating surface facility and gathering pipe network designs

“…It has been seen that variability in production from early CBM wells in Queensland began to suggest that lateral continuity of the coals, either as individual seams or as packages, was much more complex and less predictable than original expectations (Towler, et al, 2016). Fisk et al (2010) report that in the Bowen Basin of Queensland, it is not unusual for production to changes as much as 50-75 % between neighbouring wells within a few M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 kilometres.…”

“…This is also supported by work shown by Burgoyne & Clements (2014) in the variance of peak flow from CBM wells with similar key geological properties. On actual rate of gas production, Towler et al (2016) report that CBM wells in Queensland have mean gas production rates between 1 and 2 MMSCFD, with some wells exceeding 20 MMSCFD.…”