Understanding the molecular mechanisms that underlie reservoir rock-fluid interactions is playing an increasingly important role to optimize efficiencies for extraction of hydrocarbons. The Illinois basin, which sits beneath most of Illinois extending through southern Indiana and western Kentucky, contains various amounts of dolomite, limestone, sandstone, shale and clays. Due to the complex heterogeneity of the basin, in-depth studies must be undertaken to characterize and understand how the downhole fluids are interacting with the rock formation, in order to maximize hydrocarbon removal. Thus, we have developed new methods to fractionate and characterize complex crude oil mixtures using a combined strategy of chemical fractionation and advanced mass spectrometry methods combined with FTIR spectroscopy and thermal analysis with evolved gas analysis. Furthermore, in this study we investigate the rock-fluid interactions through retention of a light crude oil from the Illinois Basin by clay minerals common to oil-bearing rocks within the basin.<br/><br/>In this study, we examine the interaction of crude oil with kaolinite. The dipolar nature of kaolinite gives it the potential to interact with both polar and nonpolar oil constituents. To begin we ‘dosed’ KGa-1b kaolinite with a light crude oil from the Illinois Basin for 7 days. We then selectively fractionated the oil retained by kaolinite using a modified form of Saturate, Aromatic, Resin and Asphaltene (SARA) Analysis. We employed thermogravimetric analysis and evolved gas analysis to quantify the amount of oil retained by kaolinite. Initially, ~350 mg/g of crude oil was retained by kaolinite and this was sequentially lowered with each additional fractionation step to a final surface loading of 5 mg/g of crude oil. FTIR spectroscopy was used to study the oil constituents retained by the kaolinite after each fractionation. Finally, high resolution mass spectrometry was used to characterize each of the oil constituents eluted from the kaolinite surface. Atmospheric pressure chemical ionization mass spectrometry using CS2 was used to characterize the crude oil, each of its SARA fractions, and each fraction of the oil retained by kaolinite. The crude oil retained by kaolinite was compared with the original crude oil on the basis of average carbon number, molecular weight, and aromatic core size from mass spectrometry and of aromatic and aliphatic spectroscopic signatures derived from FTIR and Raman spectroscopy.

Molecular interactions of crude oil with clay minerals

254th National Meeting (2017)

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