Oil Sands Core
Spectral Gamma
XRF analysis directly measures the elemental concentrations of potassium(K), uranium(U), and thorium(Th) in a given rock sample. These amounts are then converted to a synthetic total gamma (XRF GR). Wireline and MWD tools measure natural gamma rays from a volume of rock in-situ, then back calculate how much K, U and Th are present. By comparing the results of down hole readings with XRF gamma, the cuttings or core can be depth shifted to their correct locations of origin. In horizontal wells, the XRF can provide a spectral gamma from drill cuttings to compliment MWD, and potentially identify if a downhole gamma tool has malfunctioned.
Radioactive “Hot” Sands
Radioactive “hot” sands are sandy intervals with high gamma readings. These sands contain heavy mineral assemblages. The radioactive heavy minerals are likely Monazite (Th and U) and Zircon (U). On wire line logs they are see as; Increased gamma, that looks like high clay. Increased grain density, that looks like decreased porosity. Increased conductivity, which looks like less hydrocarbon.
Major Elements
The major elements are used to construct a basic stratigraphy over the target zone. They represent building blocks of the main rock forming minerals and allow the client to see changes in stratigraphy before any significant processing of the data has occurred. The elements Aluminum (Al), Potassium (K) and Iron (Fe) can also be used to help determine what type of clay minerals are present.
Mineralogy
Most geoscientists and engineers that we work with are not familiar with elemental data. The use is generally limited to stratigraphic correlation. However, there is a significant body of data that, if converted to more familiar and more pertinent forms, provide a wealth of information. Reservoir properties are generally a function of the mineralogy and fabric of the rock, not simply the elemental composition. Determination of the mineralogy from the elemental data provides the user with a much more powerful tool. We employ the principles of mineralogy phase theory to construct normative mineral algorithms. High resolution sampling ensures no details are overlooked in the core.
Clay Mineralogy
The viewing side of the oil sands core is analyzed with the bitumen, so there is no loss of fines or clays.
Particle Size Distribution
Mineralogy and trace element chemistry are used to model particle size distribution (PSD). Sands with more heavy minerals are finer grained. PSD shows changes in grain size within quartz rich sands and can help to identify sand on sand contacts. XRF PSD compares favorably to Laser PSD reference data. XRF PSD is used to estimate permeability through a variation of Berg’s model (Berg, 1970).
Grain Size
Grain size can be estimated as a function the particle size distribution by binning the PSD data.
Reservoir Properties & Bitumen Analysis
Chemical analysis of oil sands core provides mineral composition, sediment source and clay typing information about the rock. This information combined with trace elements allows for the estimation of porosity, permeability, oil saturation, water/gas saturation and a degradation index (S in oil) comparable to Dean-Stark results. The completed XRF analysis of a single core can be conducted in a few days once a model is developed.