Application of Magnetic Techniques in Albertan Oil Sands Cores For Improved Reservoir Characterization

Abstract

This study assessed some novel techniques to improve oil sand reservoir characterization. The main focus was on high resolution, non-destructive, low field probe volume magnetic susceptibility measurements on slabbed core from 3 oil sands wells in northern Alberta. The results demonstrated that this technique was able to distinguish the main lithologies better than traditional borehole logging data such as gamma ray and spontaneous potential. The magnetic data also allowed estimates of the paramagnetic clay mineral illite to be determined. High resolution X-ray fluorescence (XRF) measurements were taken at the same points as the magnetic susceptibility to provide supplementary compositional information. The magnetically derived illite contents correlated with the elemental contents of iron, potassium and aluminium (all components of illite) from the XRF. The magnetically derived illite contents also correlated with available fluid permeability measurements, and provided a tool for identifying anomalous mineralogies (where the "illite" content exceeded 100%). Isothermal remanent magnetization (IRM) measurements on core samples were able to identify and quantify extremely small amounts of ferrimagnetic particles. An independent method involving low field and high field magnetic susceptibility also gave consistent results. Temperature dependent magnetic susceptibility measurements on core samples provided an improved method to identify and quantify the paramagnetic mineral contents. The temperature dependence of the magnetic susceptibility of paramagnetic minerals is important for borehole applications, since temperature generally increases with depth in a borehole. Model template curves for volume magnetic susceptibility with depth were therefore constructed for in situ borehole magnetic susceptibility applications in oil sands reservoirs.