GAB | Hydrogeological implications of fault behaviour from in-situ pressure measurements of the Horrane Fault in the Surat Basin (Great Artesian Basin, Australia)

Title: Hydrogeological implications of fault behaviour from in-situ pressure measurements of the Horrane Fault in the Surat Basin (Great Artesian Basin, Australia)
Authors:
  • Robin Viljoen, Arrow Energy
  • Brad Pinder, Arrow Energy
  • Saswata Mukherjee, The University of Queensland
  • St John Herbert, Arrow Energy
Abstract:

In order to assess the impact of faulting on the production and compartmentalisation of a coal seam gas (CSG) reservoir, seismicreflection surveys and subsequent drilling were undertaken to locate and then intersect the Horrane Fault in the eastern SuratBasin, in the Great Artesian Basin of Australia. The investigation of the Horrane Fault in the area of Cecil Plains on the DarlingDowns identified faulting at depths of 50–600 m within the Walloon Coal Measures. Pressure data collected during the drillingshow differential pressures on each side of the fault. The differential is interpreted to show depletion on the western side of thefault due to the CSG production field located west of the fault. On the eastern side of the fault, the pressures were near hydrostatic,and thus the fault is acting as a lateral seal. Regional modelling currently simulates faults as having permeability based upon thefraction of the units off-set across the fault. This would lead to exaggerated predictions of impact not supported by the data fromthis study. Conceptual models of the Surat Basin are currently based upon the premise that connectivity by direct linkages due tothe faults enhances groundwater-level changes due to water extraction and that the behaviour of the faults is poorly understood.This study represents the first detailed evaluation of fault behaviour in the eastern Surat Basin and can be used to update currentconceptual models and inform regional groundwater impact assessments.

Citation: Robin Viljoen R, Pinder B, Mukherjj S, Herbert S (2020), Hydrogeological implications of fault behaviour from in-situ pressure measurements of the Horrane Fault in the Surat Basin (Great Artesian Basin, Australia), Hydrogeology Journal, vol 28 (1), pp 161-174. https://doi.org/10.1007/s10040-019-02093-x
Keywords: Faults, Groundwater flow, Gas migration, Lineaments, Australia