Heavy Oil Horizontal
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.
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.
Clay Mineralogy
Major element composition determined by XRF can be used to obtain clay mineralogy through normative calculations.
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. This data is useful for customizing liner slot sizes.
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Reservoir Properties & Bitumen Analysis
Chemical analysis of heavy oil formations 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 and water/gas saturation. It should be noted that in this case the cuttings have been cleaned of all oil, pore water can be used as an estimate of original oil in place.