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Modifications of the petroleum system concept: Origins of alkanes and isoprenoids in crude oils: Reply

¹ Residuum Energy Inc., 1048 S. Oak Hills Way, Salt Lake City, Utah 84108
² Residuum Energy Inc., 1048 S. Oak Hills Way, Salt Lake City, Utah 84108
³ Chemical Engineering, Rice University, Houston, Chemical Engineering Department, MS-362, P.O. Box 1892, Houston, Texas 77251-1892
⁴ Energy and Geoscience Institute, 423 Wakara Way, Suite 300, Salt Lake City, Utah 84108

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
Many points of agreement are observed between our position and that of Walters et al. (2005). We all agree that petroleum is produced by the thermal decomposition of kerogen. We disagree on the whether the entire kerogen fraction yields liquid hydrocarbons or whether a specific component is largely responsible for the crude. However, a major reinterpretation of an important aspect of the petroleum system hinges on this apparently small disagreement.

The primary carbon fixers are a variety of planktonic and benthic organisms. Bacteria may attack this material during and after sedimentation. These reactions occur at rather low temperatures, and it is likely that this bacterial residue is poorly organized and is not at chemical equilibrium. Over time and with increasing temperature, diagenetic reactions occur that metamorphose the organic material into more organized stable entities. The final product before the onset of conversion to petroleum remains a complex mixture of primary and secondary products of this biological-sedimentation-diagenetic pathway.

At this point, opinions diverge. Walters et al. (2005) represent the consensus of American organic petroleum geochemists. The basic principle of this mindset is that most of the kerogen can eventually contribute to petroleum, but because of the heterogeneity of kerogen, reactions occur over time as one or another kerogen type yields its liquid hydrocarbon. This process can be modeled by the Arrhenius equation, where each constituent begins to yield its hydrocarbon product at a specific activation energy, and the process accelerates with temperature. If this is true, then total organic carbon (TOC) is a good predictor of the oil potential of a source rock.

An alternative is that specific components of kerogen, cross-linked biopolymers, are the major contributor to petroleum, with the remainder of the organic carbon contributing to natural gas. If so, the relative proportion of that component will be . . . [Full Text of this Article]