Alfred A. Christy

Maturity determination of organic matter in coals using the methylphenanthrene distribution

Abstract The distribution of phenanthrene and monomethylphenanthrenes in extracts of 15 different coals was determined by gas chromatography. The maturity as measured by vitrinite reflectance varied from 0.53% to 1.29% R 0 , covering the maturity range normally associated with the “oil window” ( 0.5–1.2% R 0 ). p ]Principal component analysis followed by factor rotation reveals that coal maturity correlates only with the distribution of the mono-methylphenanthrenes and not with the relative abundance of phenanthrene. This implies a methylphenanthrene distribution fraction (MPDF) linearly related to vitrinite reflectance for coal with maturity within the oil window.

Spectra of water in the near- and mid-infrared region

Abstract Spectra of water have been acquired in the mid-infrared (MIR) and the near-infrared (NIR) region in the temperature range 2–96°C and 4–52°C, respectively. Loading plots from partial-least-squares regression were used to locate isosbestic points in the spectra bands of water. By means of least-squares, the original spectral profiles have been resolved into two spectra, one increasing and the other decreasing with temperature. Concentration profiles of the two structurally different water associations, for the investigated temperature range, were obtained by use of evolutionary curve resolution and first-order differentiation of the MIR spectra. Utilising information from the concentration profiles obtained in the MIR, the NIR spectra were resolved. Relative concentrations were obtained using spectral intensities from the isosbestic points. The complexity in both the fundamental and overtone region of the spectra shows that both structures of water are involved in H-bonding. This result indicates a pseudo-first-order reaction in water, either between an open and a more dense state, or between a rigid, strongly H-bonded state and a more loosely H-bonded state. The cross-correlation pattern between the two regions can be ascribed to the temperature-induced variation in the concentration of the two associations.

Quantitative analysis in diffuse reflectance spectrometry: A modified Kubelka-Munk equation

Abstract The behaviour of the Kubelka-Munk equation with particle size is analysed by using mono-disperse polystyrene particles. Based on the experimental results a model is proposed to explain the diffuse reflectance spectra of powdered samples in a quantitative manner. The new model explains quantitatively the behaviour of the diffuse reflectance spectra of mono-disperse polystyrene particles in KBr. Furthermore, the results show that the model can be used to explain the diffuse reflectance spectra of mixtures of mono-disperse polystyrene spheres in KBr and of a coal sample mixture containing a distribution of particle sizes and KBr. It appears that the proposed model can be used for dilute samples in a quantitative manner.

Structural features of resins, asphaltenes and kerogen studied by diffuse reflectance infrared spectroscopy

Abstract Traditional transmittance i.r. techniques to analyse heavy fractions of source rocks such as resins, asphaltenes and kerogen can be replaced by the relatively simple and easy diffuse reflectance technique. From spectroscopic analysis, parallel information on the content between these three fractions is obtained. It appears that either heavy fractions or kerogen can be used. Furthermore, hydropyrolysis experiments have been carried out to follow the thermal evolution of the heavy fractions. In all these cases, attention was given mainly to the change in infrared absorptions arising from the elimination of carbonyl groups and increased aromatization. This is the main process taking place during late diagenesis and early catagenesis. An attempt has also been made to determine thermal maturity quantitatively, in terms of a spectroscopically calculated ratio 1,2 .

Water-in-crude-oil emulsions from the Norwegian continental shelf 7. Interfacial pressure and emulsion stability

Abstract The stability of water-in-decane emulsions stabilized by interfacially active fractions from North Sea crude oils has been investigated. It is shown that there exists a good correlation between interfacial pressure and the stability of the emulsions (ΦH2O=0.5). The interfacial pressure dependence also gives a qualitative explanation for the influence of salinity (formation water) and aromaticity of the organic phase. The graph of γo/w versus log C does not show a surfactant-like behaviour for the asphaltenes and resins.

Stabilization and destabilization of water-in-crude oil emulsions from the norwegian continental shelf. Correlation with model systems

Abstract A summary of properties of water-in-crude oil emulsions from the Norwegian Continental Shelf or model water-in-oil emulsions is given. A separation method for the indigenous surface active crude oil components based on adsorption/extraction was developed. These components and their films were characterized by M w determinations, FT-IR, Langmuir-Blodgett, surface/interfacial tension, dielectric spectroscopy and interactions with chemical destabilizers. The stability/instability properties of authentic water-in-crude oil emulsions can be reproduced by model W/O emulsions stabilized by the interfacially active crude oil fraction. Processes inside the water droplets and at the W/O interface taking place upon destabilization were followed by means of dielectric spectroscopy.

Multivariate calibration of diffuse reflectance infrared spectra of coals as an alternative to rank determination by vitrinite reflectance

Abstract Christy, A.A., Velapoldi, R.A., Karstang, T.V., Kvalheim, O.M., Sletten, E. and Telnaes, N., 1987. Multivariate calibration of diffuse reflectance infrared spectra of coals as an alternative to rank determination by vitrinite reflectance. Chemometrics and Intelligent Laboratory Systems , 2:199-207. Sixty-four randomly selected, vitrinite-rich coal samples were subjected to petrological, spectrometric and multivariate data analysis. Diffuse reflectance Fourier transform infrared spectra in a Kubelka-Munk format were reduced by a maximum entropy reduction method and were calibrated against vitrinite reflectance using partial least squares regression. Two calibration models were calculated. One model was calculated for coal samples with vitrinite reflectance from 0.38 to 1.08, i.e., including most of the maturity range defined as the “oil window”. Outliers or non-population members were identified by an iterative process, leaving a total of 41 coal samples. The cross-validated model gave an absolute prediction error of ± 0.09, a value of the same order of magnitude as the average standard deviation of the vitrinite reflectance measurements (1 s = 0.06). The second model was calculated for eighteen samples with maturity from 1.32 to 3.54. An absolute prediction error of ±0.15 was obtained, reflecting the higher uncertainty in the vitrinite reflectance measurements for the higher-ranking coals.

Determination of the Equilibrium Constant and Resolution of the HOD Spectrum by Alternating Least-Squares and Infrared Analysis

The equilibrium between H2O, D2O, and HOD in the liquid phase has been analyzed for different concentrations of the reactants by using the attenuated total internal reflectance (ATR) technique. The infrared spectroscopic profiles of the equilibrium mixtures were broken down into the contributing components by the alternating least-squares (ALS) curve resolution technique. Furthermore, the concentration profiles of H2O, D2O, and HOD were determined together with the equilibrium constant. Band assignment of the resolved HOD spectrum was further carried out. The equilibrium constant determined in this work agrees excellently with values determined by both theoretical calculations and experiments.

Quantitative determination of thermal maturity in sedimentary organic matter by diffuse reflectance infrared spectroscopy of asphaltenes

Infrared spectroscopic analysis of the asphalthenes extracted from an artificially matured Kimmeridge clay sediment (kerogen type II) reveals an excellent correlation (0.997) between temperature and a maturity parameter based on two peaks at approximately 1600 and 1700 cm−1. The change in intensity of the two peaks is discussed in terms of chemical changes of kerogen during the maturity range investigated in the present work (late diagenesis and early catagenis, i.e. %Ro increasing from approximately 0.5 to 0.85%). n nComparison with a maturity index based on the methylphenanthrene distribution shows that the spectroscopic determined parameter correlates best with temperature in the maturity range examined in this work.

Low‐pressure, automated, sample packing unit for diffuse reflectance infrared spectrometry

An automatic, low‐pressure packing unit has been designed with control of packing time and pressure to prepare powder samples for diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This unit also provides a polished packing surface that ensures constant measurement height of the sample in the spectrometer. Use of this unit coupled with sample rotation during measurement and control of particle size and size distribution, provides excellent precision in obtaining DRIFTS spectra. For example, repackings by a single person or by several untrained people gave coefficients of variation from 0.8% to 2.3% for each digital spectral value for a coal sample and from 1.3% to 3.7% for thymol blue, a sharp spectral featured organic, rather than the 15%–30% normally found for repackings of the same sample. Thus representative DRIFTS spectra can be obtained quickly and efficiently from a powder sample with a single spectrum using this low‐pressure, mechanical packing device, control of particle parame...