Energy & Fuels 1996, 10, 865
865
Book Reviews Vitrinite Reflectance as a Maturity Parameter, Applications and Limitations. Edited by P. K. Mukhopadhyay and W. G. Dow; American Chemical Society Symposium Series 570; American Chemical Society: Washington, DC, 1994; 294 pp. Vitrinite Reflectance as a Maturity Parameter, Applications and Limitations is the proceedings of a symposium sponsored by the Division of Geochemistry Inc. at the 206th National Meeting of the American Chemical Society held in Chicago, Illinois, on August 22-27th, 1993. This volume includes 16 papers from the symposium together with an overview paper by Mukhopadhyay. Vitrinite reflectance is the de facto standard for measuring organic maturation. In this technique the amount of light reflected from a carefully polished specimen of the maceral vitrinite is quantified using a light microscope equipped with suitable oil immersion objective at a magnification of about 500×. A light-sensing device, generally a photometer, is utilized to quantify the amount of light reflected. The amount of light reflected has been shown to correspond to the thermal exposure (temperature plus time) of the vitrinite. In spite of decades of meetings by the Internal Committee of Coal Petrography and other national and international groups and refinements in analytical equipment, there still exists confusion and disagreement about measurement procedures, the precision and accuracy of measurements, which vitrinite submaceral should be measured, and the importance of other factors that may affect these measurement such as bitumen impregnation. This symposium and the published proceeding reviewed here provide us with a snap shot of the current level of expertise and some of the problems in using vitrinite reflectance. This volume is divided into four sections. The first six papers on “Petrography: standardization, applications and limitations” closely adhere to the theme of the symposium and deal with techniques and problems in measuring vitrinite reflectance. In their paper “Need for Standardization of vitrinite reflectance measurements”, DeVanney and Stanton summarize interlaboratory comparison of vitrinite reflectance. The results clearly indicate that problems still exist; interlaboratory reproducibility is about 0.05% reflectance at best and 0.15% at worst. The authors argue for the need of additional standardization in all avenues. The variation in vitrinite reflectance with in samples is explored in a paper by Bensley and Crelling who convincingly demonstrate that part of the variation in vitrinite reflectance can be attributed to remnant cell structure. Stasiuk et al. suggest corpohuminite macerals derived from algae in Paleozoic rocks correlates well with vitrinite reflectance. The important and as yet unresolved question of vitrinite reflectance suppression is addressed in papers by Quick, Suarez-Ruiz et al., and Gentzis and Goodarzi. Quick argues fluorescence intensity of vitrinite may be used to resolve the degrees of vitrinite reflectance suppression and that suppression may be due to early biogenic alterations. On the other hand, both Suarez-Ruiz et al. for some Spanish coals and Gentiz and Goodarzi for Canadian coals argue that reflectance suppression is the result of adsorption of petroleum (bitumen). The second part of this volume titled “Molecular characterization of vitrinte maturation” includes six papers. These six papers, although interesting in there own right, deal with the chemistry of vitrinite and have little to do with the title of the volume or theme of the symposium. The papers by Hatcher et al., Kruge and Bensley, and Veld et al. document the effects of rank on vitrinite chemistry. Common to all three papers is the use of flash pyrolyses which brings to mind the adage that interpreting flash pyrolyses results can be likened to throwing a watch against the wall and trying to tell the time by looking at the pieces. All three papers bring new insights as to the chemistry of vitrinite, vitrinite precursors, and understanding the maturation process but clearly more work is required to
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understand these complex reactions. In papers by Hill et al. and Laggoun-Defarge et al., the results of coal pyrolyses under confined conditions are described. Hill et al. conclude that, based on dry pyrolyses, the role of confining pressure on organic maturation is secondary. Laggoun-Defarge et al. found even at 450 °C and 70 MPa the ultrafine texture of vitrinite remains turbostratic. In the last paper in this section, Sackett et al. evaluate the utility of pyrolyses followed by carbon isotope analyses for maturity analysis of kerogen in whole rock specimens. The last section of this volume, “Application of vitrinite reflectance to basin modeling”, comprises four papers. The paper by Barker and Pawlewicz is a defense of their use of Tpeak (vitrinite reflectance geothermometers, VRG) in basin modeling rather than the more commonly used kinetic models which take in to consideration burial history. These authors provide convincing evidence for the utility of Tpeak where the burial history is poorly known. Mukhopadhyay et al. compare the measured values to maturation calculated using a commercial software package for some wells in the eastern Canadian Scotian Basin. Wei et al. appear to have reinvented the Lopatin/Waples time temperature index (TTI) which they refer to as the time-temperature integral (TID), and they go on to show this method can be used in thermal history reconstruction. Arne and Zentilli review studies which have incorporated both apatite fission track and vitrinite reflectance and argue that the two techniques are complimentary and should be used in concert. Symposium compilations typically contain a mixture of good and not so good papers regardless of the editors’ efforts. This volume is no exception. It includes some important, not previously published, data such as the paper by Hill et al. but also some less noteworthy contributions. The most disappointing aspect of this volume, and presumably the symposium, is that less than half the papers really address the theme of the symposia. Surely a more appropriate title for the book could have been found. The book itself is printed on very poor quality paper but thankfully the volume includes few photographs and the quality of paper does not distract markedly from the volume. In reviewing this volume I was struck with how little true advancement has been made in either measuring and interpreting vitrinite reflectance data in the last 20 years. In addition, we are still almost equally puzzled by the chemistry and kinetics of maturation reactions. Although the numerical models may appear more sophisticated and have more subroutines, more inputs, and fancier graphics, it is not clear that the results are any more truthful than the model proposed by Lopatin some 25 years ago when the calculations could be performed on a napkin over lunch. Many of the papers in this volume could have been presented in a symposium in 1973 and not have been considered particularly innovative. This latter statement is not meant to criticize the symposia or the authors but rather that vitrinite reflectance is now a mature methodology; many of the problems with the technique as discussed in this symposium, including, reflectance suppression, reaction kinetics, chemical reactions, and interlaboratory standardization, are truly daunting. I recommend this volume to researchers working in the field of organic maturation and coal chemistry. Although I doubt all the papers in the volume will be of interest to anyone, some papers will be of interest to almost everyone. R. Marc Bustin, Department of Geological Sciences, The University of British Columbia, Vancouver, B.C. V6T 1Z4 CDN. Phone 604-822-6179; fax 604-822-66088. Email
[email protected]. EF950078E
© 1996 American Chemical Society
