Sensitive Carbonate Reservoir Rock Characterization From Magnetic Hysteresis Curves and Correlation with Petrophysical Properties
- David K. Potter (University of Alberta) | Tariq M. Al-Ghamdi (University of New South Wales) | Oleksandr P. Ivakhnenko (Kazakh-British Technical University)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- February 2011
- Document Type
- Journal Paper
- 50 - 57
- 2011. Society of Petrophysics and Well Log Analysts
- permeability, temperature dependence, anisotropy, high field measurements, anisotropy, high field measurements, magnetic hysteresis, magnetic susceptibility, magnetic susceptibility, porosity, temperature dependence, temperature dependence, porosity, magnetic hysteresis, anisotropy, magnetic susceptibility, permeability, porosity, magnetic hysteresis, high field measurements, permeability
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Recent work has shown how magnetic susceptibility and hysteresis measurements correlate with several petrophysical parameters in clastic reservoir samples. The present paper applies these techniques to carbonate samples. Carbonate rock typing can be achieved from high fieldmagnetic susceptibility, which indicates a sample’s diamagnetic plus paramagnetic mineral content. High fieldmeasurements are very sensitive and can quantify small differences in paramagnetic clay content that X-ray diffraction (XRD) or scanning electron microscopy (SEM) cannot. Temperature dependent hysteresis measurements can also identify and quantify small concentrations of paramagnetic minerals.
Experimental magnetic hysteresis curves demonstrated subtle differences between samples in a suite of Middle East carbonates. Significantl, the high fieldmagnetic susceptibility values from the hysteresis curves exhibited extremely good correlations with permeability (small variations in paramagnetic clay content seem responsible for this) and porosity. The low fieldmagnetic susceptibility values, however, did not correlate well with these petrophysical parameters merely because some samples contained small concentrations of ferrimagnetic impurities that contributed to the low fieldsignal. The low fieldpart of a hysteresis curve provides a further sensitive means of characterizing carbonate samples, and can be used to quantify these extremely small concentrations of ferrimagnetic material (down to a few parts per million) that XRD cannot.
Magnetic susceptibility values (both low and high field)for some US and North Sea carbonates were generally higher than the Middle East samples, indicating increased ferrimagnetic and paramagnetic (mainly clays) content. This suggested that the reservoir quality of the Middle East carbonates studied was generally better.
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