Background Paper on New South Wales Geology With a Focus on Basins Containing Coal Seam Gas Resources for Office of the NSW Chief Scientist and Engineer by Colin R. Ward and Bryce F.J. Kelly School of Biological, Earth and Environmental Sciences University of New South Wales Date of Issue: 28 August 2013 Our Reference: J083550 CONTENTS Page 1. AIMS OF THE BACKGROUND PAPER .............................................................. 1 1.1. SIGNIFICANCE OF AUSTRALIAN CSG RESOURCES AND PRODUCTION ................... 1 1.2. DISCLOSURE .................................................................................................... 2 2. GEOLOGY AND EVALUATION OF COAL AND COAL SEAM GAS RESOURCES ............................................................................................................. 3 2.1. NATURE AND ORIGIN OF COAL ........................................................................... 3 2.2. CHEMICAL AND PHYSICAL PROPERTIES OF COAL ................................................ 4 2.3. PETROGRAPHIC PROPERTIES OF COAL ............................................................... 4 2.4. GEOLOGICAL FEATURES OF COAL SEAMS .......................................................... 6 2.5. NATURE AND ORIGIN OF GAS IN COAL SEAMS .................................................... 8 2.6. GAS CONTENT DETERMINATION ........................................................................10 2.7. SORPTION ISOTHERMS AND GAS HOLDING CAPACITY .........................................11 2.8. METHANE SATURATION ....................................................................................12 2.9. COAL SEAM PERMEABILITY ..............................................................................12 2.10. ENHANCEMENT OF SEAM PERMEABILITY ..........................................................14 2.11. GEOLOGICAL ASSESSMENT OF CSG DEPOSITS ...............................................14 2.12. DATA COMPILATION AND RESOURCE ASSESSMENT ..........................................16 3. AN INTRODUCTION TO HYDROGEOLOGY .....................................................18 3.1. AQUIFERS AND ROCK POROSITY .......................................................................18 3.2. REGIONAL STRESS FIELDS AND FRACTURE NETWORKS ......................................19 3.3. HYDRAULIC CONDUCTIVITY AND PERMEABILITY ..................................................21 3.4. RELATIVE AND TIME-VARYING PERMEABILITY .....................................................23 3.5. SUBSIDENCE ...................................................................................................24 4. GEOLOGY OF NSW COAL BASINS...................................................................26 4.1. NATURE AND ORIGIN OF SEDIMENTARY BASINS .................................................26 4.2. COAL-BEARING SEDIMENTARY BASINS IN NEW SOUTH WALES ...........................26 4.3. ENERGY RESOURCES OF NSW BASINS .............................................................28 4.3.1. Coal Resources ......................................................................................28 4.3.2. Conventional Petroleum Resources .......................................................29 5. SYDNEY BASIN ..................................................................................................31 5.1. STRATIGRAPHY OF THE NORTHERN SYDNEY BASIN ............................................32 5.1.1. Early Permian Marine and Coal-bearing Strata ......................................32 5.1.2. Late Permian Coal-bearing Units, Newcastle Coalfield ..........................32 5.1.3. Late Permian Coal-bearing Units, Hunter Coalfield ................................33 5.1.4. Triassic Strata .........................................................................................34 5.2. STRATIGRAPHY OF THE SOUTHERN AND WESTERN SYDNEY BASIN ......................34 5.2.1. Early Permian Marine and Coal-bearing Strata ......................................34 5.2.2. Late Permian Coal-bearing Units ............................................................35 5.2.3. Triassic Strata .........................................................................................35 5.2.4. Igneous Intrusions and Lava Flows ........................................................37 5.3. STRUCTURE OF THE SYDNEY BASIN ..................................................................37 5.4. COAL SEAM GAS IN THE SYDNEY BASIN ............................................................38 5.4.1. Southern Coalfield ..................................................................................39 5.4.2. Hunter and Newcastle Coalfields ............................................................40 5.5. HYDROGEOLOGY OF THE SYDNEY BASIN ...........................................................41 5.5.1. Water Sharing Plans ...............................................................................44 6. GUNNEDAH, BOWEN AND SURAT BASINS ....................................................45 6.1. GUNNEDAH BASIN ...........................................................................................45 6.1.1. Permian Volcanics, Marine and Coal-Bearing Strata ..............................46 6.1.2. Triassic Strata .........................................................................................48 6.1.3. Igneous Intrusions ..................................................................................49 6.2. BOWEN BASIN .................................................................................................50 6.3. SURAT BASIN ....................................................................................................51 6.4. COAL SEAM GAS IN THE GUNNEDAH BASIN .......................................................52 6.5. HYDROGEOLOGY OF THE GUNNEDAH, BOWEN AND SURAT BASINS ......................52 6.5.1. Water Sharing Plans ...............................................................................53 7. GLOUCESTER BASIN ........................................................................................55 7.1. STRATIGRAPHY AND STRUCTURE ......................................................................55 7.2. COAL SEAM GAS .............................................................................................57 7.3. HYDROGEOLOGY .............................................................................................58 8. CLARENCE-MORETON BASIN .........................................................................60 8.1. STRATIGRAPHY ................................................................................................62 8.2. COAL SEAM GAS .............................................................................................64 8.3. HYDROGEOLOGY ...............................................................................................66 8.3.1. Water Sharing Plans ...............................................................................67 9. CONCLUDING COMMENTS ..............................................................................68 REFERENCES ..........................................................................................................69 APPENDIX I: Hydrogeological Modelling of CSG Impacts APPENDIX II: NSW Water Sharing Plans 1. Aims of the Background Paper This document is a background paper prepared for the Office of the NSW Chief Scientist and Engineer (OCSE), providing information and a discussion about the geological characteristics and history of NSW, with a focus on coal seam gas (CSG) resources, as part of a wider-ranging series of reports commissioned by that Office. The overall aim of the work is to define relevant geological concepts and topics, as well as to describe geological issues related to CSG formation and location in New South Wales. After a general introduction outlining the significance of Australian CSG resources, the first part of the paper provides information on the nature and properties of coal, the processes of coal seam gas formation, and basic information on hydrogeology and groundwater assessment. This is followed by an overview of the geological history and characteristics of the sedimentary basins in NSW known to contain CSG resources, including the nature and distribution of coal seams, CSG resources and CSG-related aquifers within those basins. A list of references is also included, as a guide to sources of additional information on particular aspects if required. Coverage of several topics peripheral to the main purpose of the paper is limited, partly to retain the focus on CSG geology and partly because of a paucity of information on those topics relevant to the study areas in the public domain. These include the possible extent of shale gas resources, processes for underground gasification of coal seams, geological storage of CO2 in coal (which can be carried out in conjunction with methane production), and the hydrogeochemistry of groundwaters in coal seams and associated strata. More in- depth coverage of some topics, such as hydrogeological modelling of CSG impacts and an outline of NSW water sharing plans, is provided in appendices attached to the main document. 1.1. Significance of Australian CSG Resources and Production The commercial production of CSG in Australia commenced in 1996. Since then CSG production has ramped up significantly, particularly in the last five years, to become an integral part of the upstream gas industry in eastern Australia. The major growth in both CSG reserves and production has been in the Bowen and