Unconventional petroleum resource evaluation in Queensland

Abstract

The search for unconventional petroleum resources requires a shift in the way the petroleum potential of sedimentary basins is assessed. Gas in source rocks and tight reservoirs has largely been ignored in preference for traditional conventional gas plays. Recent developments in technology now allow for the extraction of gas trapped in low-permeability reservoirs. Assessments of the unconventional petroleum potential of basins, including estimates of the potential resource are required to guide future exploration. The Geological Survey of Queensland is collaborating with Geoscience Australia (GA) and other state agencies to undertake regional assessments of several basins with potential for unconventional petroleum resources in Queensland. The United States Geological Survey methodology for assessment of continuous petroleum resources is being adopted to estimate total undiscovered oil and gas resources. Assessments are being undertaken to evaluate the potential of key formations as shale oil and gas and tight-gas plays. The assessments focus on mapping key attributes including depth, thickness, maturity, total organic carbon (TOC), porosity, gas content, reservoir pressure, mineralogy and regional facies patterns using data from stratigraphic bores and petroleum wells to determine play fairways or areas of greatest potential. More detailed formation evaluation is being undertaken for a regional framework of wells using conventional log suites and mudlogs to calculate porosity, TOC, maturity, oil and gas saturations, and gas composition. HyLoggerTM data is being used to determine its validity to estimate bulk mineralogy (clay-carbonate-quartz) compared with traditional x-ray diffraction methods. These methods are being applied to key formations with unconventional potential in the Georgina and Eromanga basins in Queensland.