Department of Geoscience, University of Calgary, Calgary, Alberta 2

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1 URTeC Control ID Number: Use of XRF Elemental Data to Quantify Mineralogy and Reservoir Properties of an Upper Cretaceous Oil and Gas Shale Reservoir, Eastern Saskatchewan and South western Manitoba Hosseininejad, Somayeh *1, Pedersen, Per K. 1, Spencer, Ronald J. 1, Nicolas, Michelle P. B. 2 1 Department of Geoscience, University of Calgary, Calgary, Alberta 2 Manitoba Geological Survey, Winnipeg, Manitoba Copyright 2013, Unconventional Resources Technology Conference (URTeC) This paper was prepared for presentation at the Unconventional Resources Technology Conference held in Denver, Colorado, USA, August The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper without the written consent of URTeC is prohibited. Summary The Cenomanian-Turonian strata, including the Favel Formation and Morden Member, in south-western Manitoba and eastern Saskatchewan were deposited along the eastern margin of the Cretaceous Interior Seaway. The succession is comprised of siliciclastic and carbonate-rich units with very different hydrocarbon source rock and reservoir properties as reflected in their different sedimentology, geochemistry and petrophysics. To characterize these different mudrock facies quantitative and qualitative geochemical analyses was carried out at variable scales to capture the heterogeneous character of these deposits. Geochemical data are generally powerful proxies for determination of source and reservoir rock properties. We apply a multi-disciplinary approach using integration of sedimentology and geochemistry to better characterize the distribution and origin of the various minerals in these heterogeneous, fine-grained deposits. To understand the geochemical aspect of these strata different techniques including energy-dispersive X-ray fluorescence (ED-XRF) and X-ray diffraction (XRD) are utilized to develop a high-resolution, whole-rock geochemical dataset. Geochemical data aid in understanding the distribution and lateral variation of sedimentary rocks, which can then be extrapolated to the reservoir facies between the two study areas. Further, complementary geochemical analyses including mass spectrometry techniques are integrated to quantify low-concentration, trace constituents and rare earth elements (REE). This approach constructs a framework for understanding the geochemical factors impacting reservoir properties and also helps in upscaling these core-scale measurements to reservoir scale. Introduction In mudstones there is a strong relationship between the relative proportions of major mineral phases and their related main and trace elements to depositional environment, ocean and formation water chemistry and organic richness. These in turn are closely linked to the mudstone reservoir properties. For example the relative proportions of silica, carbonate and clay minerals, as well as their types, has a direct impact on the reservoir characteristics such as pore type and volume, hydrocarbon storage and flow capacity. In addition, rock rheological properties are mainly dependant on mineralogical content and organic richness. The studied units including the Turonian Favel Formation is comprised of carbonate and organic-rich mudstones overlain by non-calcareous organic-rich mudstones of the Carlile Formation representing two different source rock and reservoir rock. Favel Formation can be divided in two members, the lower Keld Member and the upper Assiniboine Member. Correspondingly, Carlile Formation is comprised of lower Morden and upper Boyne Member. In this research, sedimentology and geochemistry of carbonate-rich Keld and Assiniboine members in addition to the clastic Morden Member are examined using available core wells in southwestern Manitoba and eastern Saskatchewan, as well as formation outcrops along the edge of the Manitoba escarpment (Figure 1). Geochemical data are used to better understand the reservoir properties

2 URTeC Control ID # and behavior, with respect to the mineral occurrence types and sedimentary fabric within these units. In order to better interpret and model the reservoir, the geochemical data is integrated with core observations, petrography, and well log interpretations. The different chemical and petrophysical characters of the Favel Formation and Morden Member of the Carlile Formation allow comparison and contrasting between two potential mudrock reservoir types. It is apparent that marine organic-rich shales are often composed of discrete sedimentary units within the stratigraphy column (Creaney and Passey, 1993). Geochemistry helps to better locate these shale source rocks. The here described analytical methodology can be applied to other analogous mudrock reservoirs and will contribute to our understanding of geochemical and sedimentary processes controlling mudrock deposition and its properties as a reservoir rock. Figure 1. Locations of areas studied in southwestern Manitoba (a) and eastern Saskatchewan (b) and their positions relative to the current Manitoba escarpment outcrop edge. Wells in red show the location of the cores examined in the two areas.

3 URTeC Control ID # Methodology The following methodology has been applied to core samples from the southwestern Manitoba study area. Similar techniques are being utilized on cores from the eastern Saskatchewan area for comparison and correlation purposes. Energy Dispersive X-ray Fluorescence (ED-XRF): This technique allows for quick and non-destructive analysis. A portable ED-XRF instrument (Innov-X model X-5000) was used to measure major (wt. %) and trace (ppm) elemental concentrations directly from core samples. Mineralogy is estimated from normalized data. We use this fast and inexpensive technique to establish an elemental chemostratigraphic framework for the Favel and Morden mudrocks in Manitoba. The ED-XRF method was also applied using powdered samples as a controlling technique to verify the accuracy of core sample ED-XRF data. X-ray Diffraction (XRD): XRD analysis was carried out on same samples at the University of Calgary. This technique allows direct mineral composition determinations for comparing with mineral abundance estimations from ED-XRF. Mass Spectrometry: Inductively coupled plasma mass spectrometry technique (ICP-MS) was chosen to complement the XRF data to measure the concentrations of trace elements and REEs with exceedingly low detection limits compared to conventional XRF. This analysis was done by Acme Analytical Laboratories Ltd. Available cores in southwestern Manitoba and eastern Saskatchewan were examined visually in addition to the geochemical work. Petrography was conducted using thin sections. The strata were also examined in outcrops along the edge of the Manitoba escarpment. Results and Discussion Major mineral phases within the Favel and Morden mudrocks are calcite and clay with lesser amounts of quartz. Figure 2 shows the different calculated mineral concentrations with depth. The major component of Favel Formation rocks is calcium carbonate (low magnesium calcite), which occurs in several forms. Examinations of rocks in outcrop and thin section, as well as geochemical data, serve to identify all these different carbonate components. The carbonates were categorized into two groups: biogenic (fossils) and diagenetic (cement), with the former being dominant. These different carbonate types show relatively similar bulk chemical composition and well log responses in some intervals. It is important to differentiate if the calcium carbonate occurs in form of pore occluding cement or porous fossil fragments. Carbonate even occurs in different mineralogical types including; calcite (aragonite), dolomite or siderite. Thus, identification of carbonate type and composition is important both from academic and industrial standpoint. Trace elemental composition can be largely influenced by Eh and ph conditions during and after deposition and is increasingly used for paleoceanographic studies (e.g. Anbar et al. 2007; Lyons et al. 2009). Vertical and lateral distributions of trace elements provide insight into paleoredox conditions. Based on trace element data there is a positive correlation between uranium and molybdenum, as well as TOC (Figure 3). U and Mo are usually preserved in reducing environments; conversely, manganese is usually associated with oxidizing conditions and its enrichment indicates high sediment accumulation rates, less water stratification, and therefore little to no anoxia (Ellwood, 2008). The higher concentration of titanium, in addition to K and Si, in Morden compared to Favel indicates that detrital clastic material is the main constitute of the Morden member. In routine identification and quantification of source rocks, trace elements can be used as proxies to identify organic rich/lean zones. Powell (2009) pointed out that redox-sensitive trace elements such as Cr, Ni, As, U, and Mo will be present in any anoxic environment. The abovementioned geochemical data such as ratio of biogenic carbonate to detrital silica abundance, organic carbon enrichment, and trace element concentrations support our sedimentary interpretations of Favel and Morden mudrocks. In fact, the highest biogenic carbonate productivity and organic carbon preservation potential occur during the highest water level or maximum transgression time, i.e., Favel deposition. Comparatively, the lower organic matter content in Morden confirms the clastic-rich nature with lower biogenic productivity within this unit, which indicates its occurrence during falling stages or regressive system tracts.

4 URTeC Control ID # Figure 2. Cross-plots of major element oxide composition and calculated calcite and pyrite concentrations with depth for the well W1 plus gamma-ray log curve and core lithology, as well as TOC data (after EOG Resources Canada Inc., 2004). Also, indicated different parasequence sets within the Keld and Assiniboine members. Mineralogical data are calculated from ED-XRF data. Figure 3. Trace element concentrations and their associations with total organic carbon in Favel Formation and lower part of the Morden Member, well W1.

5 URTeC Control ID # The mineralogy data shown in Figure 4 are used to categorize the Favel Formation as a carbonate-rich mudstone and Morden Member as an argillaceous mudrock. These two different rock types have different properties and require different exploitation techniques. Figure 4. Ternary diagram illustrating the relative variations of CaCO 3, Al 2O 3, and SiO 2 in the Favel Formation and Morden Member of the Carlile Formation. These reflect bulk mineralogical changes in calcite, clay, and quartz content, respectively. Conclusions Relationships in major mineral components including oxides, carbonates and sulfates can be used to identify mineral types and to characterize reservoir properties. For instance, some redox sensitive minerals and trace elements reflect variations in organic material abundance and type. The different chemical and petrophysical characters of the Favel Formations and Morden Member allow comparison and contrasting between two mudrock types. Sedimentary facies boundaries tend to correspond with changes in major mineral concentrations. The general trend of decreasing biogenic carbonate content from the Favel Formation to the Morden Member as well as a significant increase in detrital material, mainly clay, shows that the Favel Formation was deposited during a transgression phase and Morden Member was deposited during regressive stages of sea level. Mapping within a sequence stratigraphic framework will allow to understand the geometry of these systems tracts and their lateral viability. Mineral concentrations categorize the Favel and Morden as carbonate-rich mudstone and argillaceous mudstone, respectively. From a reservoir perspective, these different types of rocks have different petrophysical properties and subsequently different reservoir properties. Degree of brittleness, pore volume and type as well as permeability, and hydrocarbon storage capacity are partly controlled by mineralogy. The developed analytical methodology will contribute to our understanding about geochemical and sedimentary processes forming different mudrock types and the way these processes impact our reservoir properties.

6 URTeC Control ID # References Anbar, A. D., Duan, Y., Lyons, T. W., Arnold, G. L., Kendall, B., Creaser, R. A., Kaufman, A. J., Gordon, G. W., Scott, C., Garvin, J., and Buick, R., 2007; A Whiff of Oxygen before the Great Oxidation Event? Science v: 317, p: Creaney S. and Passey Q.R., 1993; Recurring Patterns of Total Organic Carbon and Source Rock Quality within a Sequence Stratigraphic Framework, AAPG Bulletin, v: 77, p: Ellwood, B. B., Tomkin, J. H., Ratcliffe, K. Y., Wright, M., and Kafafy, A. M. 2008; High Resolution Magnetic Susceptibility and Geochemistry for the Cenomanian/Turonian Boundary GSSP with Correlation to Time Equivalent Core. Palaeogeography, Palaeoclimatology, Palaeoecology, v: 261, p: Lyons, T. W., Reinhard, C. T., and Scott, C., 2009; Redox Redux, Geobiology v: 7, p: Powell, W., 2009; Comparison of Geochemical and Distinctive Mineralogical Features Associated with the Kinzers and Burgess Shale Formations and their Associated Units. Palaeogeograhy, Palaeoclimatology, Palaeoecology, v: 277, p: