Using Chemometrics and Geochemistry to Assess Heavy Oil Fluid Heterogeneity in Southeastern Mexico Heavy Oil Fields
Date
2021-01-06
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Abstract
Declines in heavy oil production from the Tertiary reservoirs of southeastern Mexico relate predominantly to fluid heterogeneity between production wells. This work uses chemometrics to analyze whole heavy oil geochemical compositions to assess fluid heterogeneity in order to optimize well placement and oil field management. A biodegradation parameter is derived from the bicyclic sesquiterpanes to fill in the gap of the Peters and Moldowan biodegradation levels (PM level) 4–5, where diagnostic indicators are missing. Then, biodegradation sensitive hydrocarbon and non-hydrocarbon compound classes are identified and used to develop biodegradation indicators for different oil fractions. These parameters are subsequently integrated by principal component analysis (PCA) to generate a whole oil composition-based biodegradation parameter that magnifies oil compositional variations and enables a higher resolution estimation of biodegradation levels. To deconvolve complex oil biodegradation, charging and mixing history, exploratory factor analysis is applied, incorporating fresh oil components and the biodegradation indicators for different oil fractions. This method allows elucidation and a broad classification of biodegradation, charging and mixing scenarios of the studied oils. Comprehensive fluid heterogeneity characterization is realized by PCA and hierarchical clustering analysis using whole oil compositions. Accordingly, compositionally similar oils produced from correlated horizons are grouped for each production zone identified using geological and geophysical techniques. Oil heterogeneity assessment reveals biodegradation as the predominant control on fluid heterogeneity. The workflow of using chemometrics to analyze whole oil compositions to assess heavy oil fluid heterogeneity can be extended to heavy oil reservoirs worldwide. Alternating least squares (ALS) method is exploited to address the common issue of oil-based drilling mud contamination during reservoir development. Oil end member amount in the cuttings extract mixtures is suggested by PCA and end member fractions are calculated by the ALS model. Geochemical characterization of the cuttings extracts highlights overwhelming drilling fluid components and severely diluted reservoir oil biomarkers. Authentic reservoir oils in the cuttings extracts are recognized by biomarker correlation between the ALS-determined oil end members and the produced oils from the same oil field. Reservoir oil viscosity encountered by the cutting well is roughly predicted based on viscosities of the associated oils.
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Heavy oil, fluid heterogeneity, biodegradation estimation, oil biodegradation, charging and mixing deconvolution, GC–MS, FTICR–MS, chemometrics, oil-based drilling fluid contamination
Citation
Yin, M. (2021). Using Chemometrics and Geochemistry to Assess Heavy Oil Fluid Heterogeneity in Southeastern Mexico Heavy Oil Fields (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.