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Applications:Heavy Oil

For a more indepth look at XRF in the oilsands please follow this link: CSPG Poster Oil Sands 2016

The goal of XRF Solutions is to use X-ray fluorescence (XRF) technology to provide chemical logs in vertical exploration wells. These logs help to increase hydrocarbon production through better placement of SAGD well pairs. XRF analyses are a rapid and relatively inexpensive way to gather large quantities of information at low cost per sample. Bulk rock chemistry is gathered in terms of both major elements and trace elements. Algorithms are applied to the data to provide geologic interpretations and fluid analysis.

Chemical analysis of heavy oil 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, oil saturation, water/gas saturation and a degradation index (viscosity or API proxy) 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.

Normative mineral calculations are used to calculate the mineralogy of each sample from elemental data. Rock composition is then used to divide the core into unique stratigraphic packages. In figure A, five sand units are identified by XRF analysis. It is difficult to distinguish major differences in composition or provenance in sand units 1-4 viewed in core . These sand units all appear black due to high bitumen content. Identification of differences in mineral assemblages, clay types, total clay and trace elements are used to distinguish each stratigraphic horizon.

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Figure A. Mineralogy from a Vertical Well in the McMurray Formation. 

XRF data can also be used to determine bitumen characteristics based on trace elements and mineralogy.  XRF calculated values are confirmed by comparison with laboratory measured values from Dean-Stark analyses. Figure B shows XRF values (colored lines) compared with lab measured values (diamonds) and a resistivity log (black line).  There is a strong correlation between the two data sets for most of the well. Differences near the top of “sand 2” and bottom of “sand 1” can be related to the degree of oil degradation. Viscosity measurements and  wire line logs can also be used for comparison. 

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Figure B. Bitumen Properties from Core Analysis in the McMurray Formation.

The reservoir quality graph (Figure C) highlights information that is most pertinent to the client. In a glance, the graph shows the amount of clay, carbonate and quartz present along with how these affect the porosity. Individual sand packages can be distinguished using quartz/Zr ratio. Finally the calculated oil saturation and degradation estimates are also provided in order to locate the best reservoir rock for well placement.  Chemical logs are useful in mapping particular sand/shale packages, determining depositional environments and estimating oil saturation/quality quickly at low cost.  These analyses also have benefits for delineation drilling in heavy oil mining operations.  XRF can provide quantitative core measurements at the mine site with rapid turnaround times and without the need for transporting the samples to a conventional lab.

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Figure C. XRF Reservoir Quality Factors from a Vertical Well in the McMurray Formation.