The Walloon coal seam gas play, Surat Basin, Queensland
Damien Ryan A , Andrew Hall A , Leon Erriah A and Paul Wilson AQGC
The APPEA Journal 52(1) 273-290 https://doi.org/10.1071/AJ11020
Published: 2012
Abstract
Extensive drilling of the Walloon Subgroup for coal seam gas (CSG) during the last decade has revealed a world-class CSG play on the northern flank of the Surat Basin. Resources discovered in the Walloon Subgroup exceed 30 TCF; this gas now underpins four CSG-to-liquefied natural gas (LNG) projects.
Results to date have revealed the highly heterogeneous nature of the Walloon Subgroup and its associated coal properties. The Walloon Subgroup is typically 350 m thick and contains an average of 30 m of net coal that is interbedded with a range of clay-rich, fluvio-lacustrine lithologies. The most prospective area of the play occurs down-dip and adjacent to the Walloon subcrop edge, where high permeability exists combined with a thick section of net pay. Coals in the Walloon Subgroup are low rank (0.35–0.65% Ro) with gas contents ranging between 1–15 m3/tonne (dry ash-free). Average coal ply thickness is 30 cm, making correlation and prediction of reservoir properties difficult. Reservoir properties—including permeability, gas content and saturation—differ as a result of compositional variability of the coal seams and also the tectonic history.
Mapping of sparse 2D seismic data has highlighted the distribution of major structural features throughout the basin. Coal fracture permeability ranges from less than 0.1 mD to more than 2,000 mD, and mapping has identified areas where permeability appears to be enhanced on structures that have undergone mid Cretaceous–Eocene deformation.
Damien Ryan has a BAppSc from QUT (1999) and a BSc (Hons) majoring in petroleum geology from the NCPGG/University of Adelaide (2000). Upon graduation he joined Geoscience Australia and worked on projects relating to the geology and petroleum prospectivity of Australia’s offshore basins. He joined MBA Petroleum Consultants in 2007 and worked on projects ranging from small conventional-field assessments to CSG prospectivity; however, he was largely focused on CO2 storage assessments, including the Queensland CO2 Geological Storage Atlas. In 2009 he joined QGC—a BG Group business—and is now a principal geologist and the Geological Modelling team leader, focused on appraisal and development of the Walloon Subgroup for the QCLNG project. damien.ryan@bg-group.com |
Andrew Hall has a BSc (Hons) in Geophysics from the University of Leeds (2003) and an MSc in Petroleum Geoscience from Imperial College, London (2004). Upon graduation he joined BG Group as a geophysicist on the world-renowned graduate development program. He has held several asset geophysicist roles in the group, spanning new venture evaluations, exploration, appraisal well planning and field development with particular experience and interest in prospect evaluation, rock physics and seismic amplitude interpretation. He is now a principal geophysicist working at QGC—a BG Group business—focused on the geophysical evaluation of the Walloon Subgroup for the QCLNG project. Andrew.Hall@bg-group.com |
Leon Erriah has a BSc (Hons) in Petroleum Geosciences from the University of the West Indies, Trinidad and Tobago (2005). He joined BG Group through their graduate program in 2005, working on a variety of projects in offshore and onshore basins in Trinidad, including one assignment in BG’s UK asset (Buzzard field, North Sea). Leon returned to Trinidad in 2007 and worked on one of the major gas producing assets in the North Coast Marine Area, leading a six-well horizontal development campaign. In 2010 he joined QGC on international assignment and is now a lead development geologist, focused on reservoir modelling of the Walloon Subgroup for the QCLNG project. Leon.Erriah@bg-group.com |
Paul Wilson has a BAppSc from QUT (1999) and a first class Honours degree in Petroleum Geology and Geophysics from the NCPGG (2000). At the completion of his degree, Paul joined AGSO and worked on the GEODISC Project, evaluating the regional prospectivity of CO2 sequestration in Australia. After 18 months in Canberra, Paul joined Sunshine Gas—a newly ASX-listed small cap company focused on CSG and tight gas exploration in the Bowen Basin. Paul gained vast amounts of operational experience during his time with Sunshine Gas and in late 2006 joined MBA Petroleum Consultants. Paul consulted for numerous companies focusing on CSG exploration in the Bowen and Surat basins while at MBA. In late 2008, Paul joined BG Group (Australia) and worked on several new venture projects, culminating in the acquisition of Pure Energy and Queensland Gas Company. Paul is now the manager of development geosciences at QGC—a BG Group business—and is focused on delivering gas from the Surat Basin for the QCLNG Project. PaulB.wilson@bg-group.com |
