Biodegradation of Crude Oils in Reservoirs

Connan, Jacques

doi:10.1016/b978-0-12-032001-1.50011-0

Cited by 338 publications

(224 citation statements)

References 27 publications

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“…The enhanced degradation of the proposed isoprenoid algaenan component in the kerogen is remarkable. Biodegradation of oils, although not directly comparable to oxic degradation of macromolecular matter, typically results in an increased abundance of the isoprenoid alkanes and a decrease in abundance of the nalkanes (Connan, 1984). The reason for this apparent contradiction is not yet clear.…”

Section: Postdepositional Oxidation Effect On the Bulkmentioning

confidence: 90%

Changes in kerogen composition across an oxidation front in Madeira Abyssal Plain turbidites as revealed by pyrolysis GC-MS

Damsté¹,

Hoefs²,

Leeuw³

et al. 1998

Proceedings of the Ocean Drilling Program, 157 Scientific Results

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Isolated kerogens from Madeira Abyssal Plain turbidite samples were qualitatively and semiquantitatively studied by means of analytical pyrolysis for the effect of oxygen exposure on organic matter preservation. The initial organic matter in the turbidite is very homogeneous and relatively high and offers an ideal case for the study of oxygen effects on organic matter preservation without the usual complications of varying sources or sedimentation rates and bioturbation. From all four studied turbidites, one sample from the oxidized part of the turbidite was compared with two samples from the unoxidized part. The aliphatic character of the kerogens after postdepositional oxidation has increased significantly, as revealed by the abundance of the n-alkanes and n-alk-1-enes in the oxidized turbidite. At the same time, the contribution of the isoprenoid alkanes and alkenes and the alkylthiophenes to the pyrolysate has decreased significantly. The relative abundances of alkylbenzenes, alkylnaphthalenes, alkylphenols, alkylindenes, and alkan-2-ones in the pyrolysates have remained relatively constant upon oxidation. The alkylbenzene, alkylphenol, alkylnaphthalene, n-alkane, and n-alk-1-ene, isoprenoid alkane, and alkene internal distributions are substantially altered in the oxidized samples. This study shows that postdepositional oxidation of sedimentary organic matter by oxygen is far more severe than by sulfate alone. Furthermore, it is clear that oxidation of the organic matter is, to a significant degree, selective.

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Section: Postdepositional Oxidation Effect On the Bulkmentioning

confidence: 90%

Changes in kerogen composition across an oxidation front in Madeira Abyssal Plain turbidites as revealed by pyrolysis GC-MS

Damsté¹,

Hoefs²,

Leeuw³

et al. 1998

Proceedings of the Ocean Drilling Program, 157 Scientific Results

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“…This demonstrates that as temperature increases, so does the window of opportunity with respect to H 2 and acetate. Clearly this is only part of the story as it is well known that at temperatures in excess of 80-90 1C, in-reservoir petroleum biodegradation apparently ceases (Connan, 1984;Head et al, 2003), illustrating that above these temperatures biological factors are more important than thermodynamic factors in controlling methanogenic hydrocarbon degradation. The windows of opportunity with respect to acetate and H 2 , the central intermediates in methanogenic alkane degradation, have been summarized for the range of processes that are feasibly involved in methanogenic alkane degradation.…”

Section: Thermodynamic Constraints J Dolfing Et Almentioning

confidence: 99%

Thermodynamic constraints on methanogenic crude oil biodegradation

2007

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Methanogenic degradation of crude oil hydrocarbons is an important process in subsurface petroleum reservoirs and anoxic environments contaminated with petroleum. There are several possible routes whereby hydrocarbons may be converted to methane: (i) complete oxidation of alkanes to H 2 and CO 2 , linked to methanogenesis from CO 2 reduction; (ii) oxidation of alkanes to acetate and H 2 , linked to acetoclastic methanogenesis and CO 2 reduction; (iii) oxidation of alkanes to acetate and H 2 , linked to syntrophic acetate oxidation and methanogenesis from CO 2 reduction; (iv) oxidation of alkanes to acetate alone, linked to acetoclastic methanogenesis and (v) oxidation of alkanes to acetate alone, linked to syntrophic acetate oxidation and methanogenesis from CO 2 reduction. We have developed the concept of a 'window of opportunity' to evaluate the range of conditions under which each route is thermodynamically feasible. On this basis the largest window of opportunity is presented by the oxidation of alkanes to acetate alone, linked to acetoclastic methanogenesis. This contradicts field-based evidence that indicates that in petroleum rich environments acetoclastic methanogenesis is inhibited and that methanogenic CO 2 reduction is the predominant methanogenic process. Our analysis demonstrates that under those biological constraints oxidation of alkanes to acetate and H 2 , linked to syntrophic acetate oxidation and methanogenesis from CO 2 reduction offers a greater window of opportunity than complete oxidation of alkanes to H 2 and CO 2 linked to methanogenic CO 2 reduction, and hence is the process most likely to occur.

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“…Hydrocarbons are preferentially destroyed during biodegradation. The selective consumption of saturate and aromatic hydrocarbons during biodegradation is well documented (Connan, 1984;Hunt, 1995;Wenger et al, 2002;Peters et al, 2005). In general, normal alkanes are preferentially consumed, followed by branched alkanes, monocyclic paraffinic and monoaromatic hydrocarbons, multi-ring naphthenic and polynuclear aromatic hydrocarbons and finally non-hydrocarbons (Fedorak and Westlake, 1984a,b;Huang et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…Anaerobic biodegradation of crude oil is a common phenomenon occurring in subsurface oil reservoirs (Aitken et al, 2004). It is widely accepted that microbial degradation significantly alters the molecular composition and physical properties of crude oil, leading to a decrease in low molecular weight saturates and aromatics and an increase in polars, oil density, viscosity, sulfur content and acidity (Evans et al, 1971;Connan, 1984;Meredith et al, 2000;Peters et al, 2005). Hydrocarbons are preferentially destroyed during biodegradation.…”

Section: Introductionmentioning

confidence: 99%