Oral Presentation Australasian Groundwater Conference 2017

Borehole magnetic resonance logging tools and hydrogeological study in the Illawarra coal measures and Hawkesbury Sandstone of the Sydney Basin (246)

Adam Lloyd 1 , Timothy Hopper 1 , Benjamin Birt 2 , Mark Krejci 3 , Melinda Lett 3 , Thomas Neville 1
  1. NMR Services Australia Pty Ltd, Perth, WA
  2. Kinetic Logging Services Pty Ltd, Perth, WA
  3. South 32, Perth, WA

Borehole Magnetic Resonance (BMR) logging tools have been used routinely in the oil and gas industry for decades. Their ability to give lithological independent porosity and fluid property information makes them invaluable in assessing a reservoir’s properties. BMR tools utilise a magnetic resonance technique to measure signals from hydrogen nuclei in water. This signal measures the total porosity as well as a distribution or relaxation rates (T2) of the nuclei within the pore spaces. From the measured T2 decay, a T2 distribution curve can be obtained that is related to pore size. This pore size can be separated into specific retention (bound fluid) and specific yield (free fluid). Empirical formulas can then be used to determine the hydraulic conductivity of the formation. Until recently BMR tools have been large and expensive, inhibiting their use in mineral mining and hydrological sectors. However, with the introduction of a slim hole BMR tool this data is now available to the wider market. This paper describes the principles of BMR and how to interpret the measured data. A basic hydrogeological characterisation model of some coal measures and overburden strata using BMR data is also presented with examples including aquifer/aquitard definition, hydraulic properties analysis (T, k, Sy). The hydraulic properties are compared with other testing techniques (packer testing and cores). Issues with functions of scale of measurements are addressed as are relevance to hydrogeological characterisation. Finally it is shown how the data can be used in conceptual and numerical modelling applications and how the inclusion of BMR data can improve data models and decrease the reliance on traditional aquifer testing methods.

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