--> Finding Extra Value in Elemental Concentration Data: a Mudrock Mineral Model for the Duvernay Formation Unconventional Reservoir

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Finding Extra Value in Elemental Concentration Data: a Mudrock Mineral Model for the Duvernay Formation Unconventional Reservoir

Abstract

Quantification of mineralogy is a fundamental step in evaluating fine-grained unconventional hydrocarbon reservoirs. However, large data sets are more often composed of elemental concentration measurements such as inductively coupled plasma - mass spectrometry (ICP-MS) and x-ray fluorescence (XRF) rather than direct mineralogy measurements such as x-ray diffraction (XRD) typically due to differences in time required for sample preparation, analysis, and cost. This study uses samples from the Duvernay Formation of western Canada to develop a methodology that estimates 11 mineral phases from elemental concentration data. The high resolution data set is integrated with porosity measurements to understand the influence of mineralogical heterogeneity on reservoir quality.

Hundreds of core samples from 3 wells have been analyzed using ICP-MS, supplemented with XRD, scanning electron microscopy - electron dispersive x-ray spectroscopy (SEM-EDS), and Rock-Eval pyrolysis. Step one estimated quartz, carbonates, aluminosilicates, pyrite, apatite, and rutile based statistical analysis of ICP-MS and Rock-Eval total organic carbon (TOC) and mineral carbon (MinC) (Wang et al., 2016). Step two distinguished detrital quartz, biogenic silica, K-feldspar, albite, micas, illite, and chlorite based on the contribution of these minerals to the ICP-MS SiO2 and Al2O3 concentrations.

The mineralogy output correlates well to accompanying lithofacies classifications from core observation, and a previously published stratigraphic framework (Knapp, 2016). Samples with high biogenic silica contain crushed and recrystallized siliceous radiolaria in thin section and abundant microcrystalline quartz in SEM. Integration of mineralogy results with porosity measurements from helium porosimetry, mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR), and focused ion beam - scanning electron microscopy (FIB-SEM) image analysis has shown that biogenic silica has a direct influence on the development and preservation of organic-hosted porosity.

References:

Knapp, L.J., 2016. Controls on organic-rich mudstone deposition: the Devonian Duvernay Formation, Alberta, Canada. M.Sc. thesis. University of Alberta, Edmonton, Canada.

Wang, X., Sanei, H., Dai, S., Ardakani, O., Isinguzo, N., Kondla, D., Tang, Y., 2016. A novel method to estimate mineral compositions of mudrocks: A case study for the Canadian unconventional petroleum systems. Marine and Petroleum Geology 73, 322-332.