Paul W. Brooks

Biological marker and conventional organic geochemistry of oil sands/heavy oils, Western Canada basin☆

Abstract Forty-three samples of oil sands/heavy oils from most of the major Cretaceous deposits and the Upper Devonian Grosmont Formation of the underlying “carbonate trend”, have been examined by gas chromatography and gas chromatography-mass spectrometry. Major organic geochemical differences observed between samples/deposits include the presence or absence of n-alkanes and isoprenoid alkanes, together with changes in the distributions of biological marker compounds. These differences reflect the degree of biodegradation suffered by the deposits. As noted earlier by others, there is a trend toward increased biodegradation from west to east in the basin. Three geochemical factors demonstrate that at least the Cretaceous samples are strikingly similar to one another, once the effects of biodegradation are discounted. These factors are the carbon number distribution of steroidal alkanes (C27, C28, and C29 diasteranes); the presence of 28,30-bisnorhopanes; and the relative abundance of 28,30-bisnorhopanes and gammacerane as compared with the ubiquitous 17α(H)-hopanes. These distinctive biomarker compositions are ratios indicate that the same or very similar sources generated the Cretaceous oil sands/heavy oils, despite the enormous volumes and their widespread geographic and stratigraphic distribution. The extent of isomerization of regular steranes and hopanes indicates that the bitumens show the same general level of maturity. All these data suggest that the Cretaceous bitumens were derived from a mature, conventional oil which was in turn derived from a presently unknown source fecies. This oil must have migrated over large distances, suffering extensive biodegradation in place and possibly during migration. There appear to be at least two mechanisms of biodegradation that the biomarkers have undergone in the Cretaceous oil sands/heavy oils. Most samples from which regular steranes have been removed by extensive biodegradation do not show 25-norhopanes. In four Wabasca Deposit Grand Rapids A sand samples, however, 25-norhopanes are present in variable amounts relative to regular hopanes, despite the fact that three of these four samples still contain regular steranes. Possible candidates for source facies may be present in the Mesozoic clastic succession as suggested by others, but systematic work at all stratigraphic levels is required to discover a source facies with the requisite geochemical properties and the potential of having generated the enormous volumes of oil contained within the oil sands and heavy oil reservoirs of the Western Canada Basin.

Unusual biological marker geochemistry of oils and possible source rocks, offshore Beaufort-Mackenzie Delta, Canada

Abstract Tertiary oils and source rocks from the offshore Beaufort-Mackenzie Delta have been examined for their biological marker content. The triterpane and sterane distributions suggest a predominant land plant contribution to the oils. The oils range in maturity from extremely immature to moderately mature 18(α)H-Oleanne is a major triterpane of the oils together with probable bisnorlupanes, and an excellent correlation is observed in the concentration of these components in individual oils. An excellent correlation is also observed between the concentration of bisnorlupanes and oil maturity, based on sterna and triterpane maturation parameters, suggesting that the decrease in relative concentration of these components with increasing maturity is a result of progressive dilution by hydrocarbons generated by the cracking of kerogen. Only one formation in cores taken from the delta has been found to contain bisnorlupanes, and were present they are the dominant hydrocarbons of the branched/cyclic fraction.

Triassic oils and potential Mesozoic source rocks, Peace River Arch area, Western Canada Basin

Abstract Triassic oils and their potential Mesozoic source rocks in the Peace River Arch region (Western Canada Basin) have been examined using various analytical techniques. Triassic oils are divided into two groups, 1 and 2, on the basis of biomarker composition. Triassic outcrop samples from the Rocky Mountain Foothills are mature to overmature, and contain Type II/III organic matter with TOCs ranging from 0.1 to 15.0 wt% and HI values up to 445. Subsurface core samples from the Triassic Montney Formation are mature to overmature with TOCs (rarely) up to 2.8 wt% and HI values up to 398. The Triassic Doig Formation has good to excellent source potential and moderate to high maturity, with TOC values over 5.0 wt% and HI values commonly in excess of 300. The Jurassic “Nordegg Member” ranges from early mature to overmature, with TOCs as high as 23.5 wt% and HI values greater than 600 where maturity is low. Oil-source rock correlations are established, based on biomarker signatures, between the Group 1 oils and the Doig Formation. Group 2 oil was sourced by the “Nordegg Member”

Correlation of the Canol Formation source rock with oil from Norman Wells

Abstract The source of the oil at Norman Wells has long been assumed to have been the Canol Formation and/or the Bluefish Member of the Hare Indian Formation. These two units are stratigraphically above and below the Kee Scarp Formation reservoir unit respectively, and are both bituminous shales. A wide range of analytical techniques including Rock-Eval pyrolysis, solvent extraction and fractionation, capillary gas chromatography, gas chromatography-mass spectrometry, and white light and fluorescence microscopy has been used to characterize core samples of these two units and two samples of crude oil from the Norman Wells field. Most of the analytical techniques were insufficiently refined to either differentiate the extracts from each other or to make a definitive oil/source rock correlation. Collision activated decomposition coupled with multiple ion detection mass spectrometry (GC-MS-MS) did provide sufficient chemical compositional detail of the oils and the two potential sources to demonstrate that the Canol Formation has been the effective source of the Norman Wells oil whereas the Bluefish Member has not. Petrological analysis of the organic fractions also indicates that although the bulk organic composition of both units may be classified as Type II organic matter, significant differences exist between them. The Bluefish Member contains substantial amounts of megaspores, whereas the organic matter in the Canol Formation is largely phytoplankton debris. The level of thermal maturity of the core samples ranges from immature to moderately mature in the vicinity of the Norman Wells field to overmature for the samples obtained to the west and north of the field. The level of thermal maturity of the oil was observed to be somewhat higher than that of the samples of the source formation directly above the field. It was thus inferred that some lateral migration from more mature areas has occurred but the extent of this migration was not necessarily more than a few to tens of kilometers.

Preliminary results from a field experiment investigating the fate of some creosote components in a natural aquifer

Abstract Creosote, a distillation product of coal tar, is made up of an extremely complex mixture of phenols and polycyclic aromatic compounds (PAC) which include polycyclic aromatic hydrocarbons (PAH) and nitrogen, sulphur and oxygen (NSO) containing heterocyclics. It is considered to be an environmental hazard. This report presents some preliminary results from a large field experiment that is evaluating the mobility, persistence and fate in groundwater of compounds present in coal tar creosote. This involved setting up a long-term field experiment where a limited plume of contaminated ground water was created by placing creosote into an extremely well characterized sand aquifer. The original creosote was dominated by PAH components with minor amounts of NSO containing PAC. The concentration of the dominant nitrogen heterocyclic (quinoline) was only 10% of the abundance of the major PAH components (naphthalene and phenanthrene). Analysis of groundwater samples collected 278 days after the emplacement of the creosote shows that with increasing distance from the source the concentration of naphthalene is reduced while that of quinoline increases, eventually becoming dominant. A similar trend was also observed for samples collected after 471 days and this can be related to the relative aqueous solubilities and mobility of the two compounds. Also observed in the outermost 471 day samples was the presence of quinolinone which is believed to be an aerobic metabolite of quinoline. Strategies for the final part of the project which involve cleaning up the Borden experimental site are briefly discussed in light of these results.

Hydrocarbon potential of Middle and Upper Devonian coals from Melville Island, Arctic Canada☆

Abstract Some of the oldest coals in the world are found within the Middle to Upper Devonian clastic wedge of the Canadian Arctic Archipelago. The coals investigated here occur in the Weatherall, Hecla Bay and Beverly Inlet formations on western Melville Island and range in age from Late Givetian to Middle Frasnian. Many of these coals are rich in liptinite macerals, particularly sporinite and hence can be termed canned coals. Both elemental and Rock-Eval analysis indicate these coals have the potential to generate liquid hydrocarbons. A good correlation between % liptinite with both H/C or Hydrogen Index is observed up to about 50% liptinite after which the latter two parameters level off. The coals range in maturity from 0.61 to 0.87% R o and hence should be in the oil window. The amounts of hydrocarbons that can be extracted from the coals when expressed in mg/g organic carbon are very low, suggesting that they are poor source rocks for oil. All the extracts except for the most mature and vitrinite-rich sample show high pr/ph ratios and biomodal n -alkane distributions. A cannel coal from The Beverley Inlet Formation has a very unusual triterpane distribution that includes regular, AB-ring desmethyl and AB-ring methyl hopanes. Steranes are in very low concentrations compared to hopanes in all samples. The relative abundance of C 28 and C 29 steranes appears to be influenced by maceral composition. Hydrous pyrolysis at 330°C for 72 h generated greater amounts of hydrocarbons from the coals suggesting they could be the source of liquid hydrocarbons at greater maturities. The hydrous pyrolysis experiments also indicate that thin-walled spores are more reactive than thick-walled spores at lower temperatures. The coals on Melville Island are not thought to be significant source rocks for the oil and gas occurrences in this area of the Canadian Arctic because they make up only a very small fraction of the total sedimentary package.

Chemical and petrological properties of some liptinite-rich coals from British Columbia

Abstract Chemical and petrological analyses were carried out on several British Columbia coals which are known as ‘needle’ coals because of the pine needle morphology exhibited on weathering. The object was to determine the nature of the precursor and thus to identify the component maceral as resinitic or algal. Infrared spectroscopy, saturate fraction gas chromatography, pyrolysis chromatography, gas chromatography-mass spectrometry, organic elemental analysis and reflectance and fluorescence microscopy were used. While the i.r. properties are consistent with previously published results on resinite, the other chemical results suggest that the present materials are not obviously related to any given member of the liptinite group of macerals. High concentrations of extractable hopanoid hydrocarbons are interpreted as resulting from high contribution to the biomass by bacterial debris. The petrological results suggest that the main constituent of the ‘needles’ can be best described as bituminite II or III derived from non-algal lipids. This conclusion is also supported by the observed associations of the other identifiable macerals. The results indicate that the ‘needles’ have been chemically and petrologically homogenized from a liptinite-rich precursor with minimal algal input. The present morphology may have been preserved from resin rodlets which have been severely altered by catagenetic or biological mechanisms or both.

Biomarker characterisation and hydrous pyrolysis of bitumens from Tertiary volcanics, queen Charlotte islands, British Columbia, Canada☆

Abstract A number of bitumen samples have been recovered from vugs and fractures in outcropping Tertiary basalts of the Queen Charlotte Islands off the west coast of British Columbia, Canada. n -Alkanes and acyclic isoprenoids are not present and the polycyclic biomarker distribution of the four samples analyzed by GC and GC-MS has been altered. One sample contains no remaining recognizable biomarkers. Two bitumens were also obtained from Lower Jurassic potential source rocks, including one from the Sandilands Formation, which was considered previously to be the most likely source of the Tertiary bitumens. Although these two bitumens were also taken from outcrops, they are considerably less biodegraded. The Sandilands Formation bitumen contains 28, 30-bisnorhopanes and since these compounds were not detected in the Tertiary bitumens, there is no evidence from the initial results for a Sandilands Formation contribution to the hydrocarbons in the Tertiary basalts. The presence of 18α(H)-oleanane in the saturate fraction of two of the Tertiary bitumens from widely separated locations indicates that they are at least partially sourced from Tertiary organic matter. Because the distribution of biomarkers in some samples has been severely affected by biodegradation, the asphaltenes of the bitumens were hydrously-pyrolysed and the saturate fractions of the resulting pyrolysates analysed for possible additional information on the origin of the bitumens. The pyrolysates from the more degraded samples contain compounds not detected in the saturate fractions of the original bitumen and show some of the expected characteristics of the original non-degraded bitumen. However, the compounds most useful for correlation are not present in the pyrolysates apparently due to their non-incorporation into the kerogen macromolecule. Our results suggest that hydrous-pyrolysis of asphaltenes is of limited use in the correlation of biodegraded samples and in determining their origins.

Aspects of biomarker analysis by gas chromatography/mass spectrometry with selective metastable ion monitoring : Part 2. Information contest of biomarkers in some light oils

Abstract The information content of steranes and pentacyclic triterpanes is extracted by means of eigenvector (factor) analysis. Steranes carry information different from that of hopanes even though they both provide information about the maturity of the source rock. Moretanes and 20R hopanes provide similar information which differs from that of 20S hopanes. The steranes carry somewhat different information, which is opposite to that carried by a series of unidentified triterpanes. The diacholestanes and cholestanes yield different types of information.

Aspects of biomarker analysis by gas chromatography/mass spectrometry with selective metastable ion monitoring : Part 1. Experimental Techniques

Abstract Biological markers such as steranes and triterpanes in source rocks and oils are important because they reveal the origin, alteration and maturation history of geological organic matter. Metastable multiple ion detection combined with high-resolution capillary-column gas chromatography provides a better solution to some of the interference problems involved than more conventional methods. The method is sensitive and allows separation by carbon number of homologous series; minor amounts of diagnostic biomarker components of crude oils and rock extracts can be estimated with no, or very little, sample clean-up. The limitations of the method are also discussed.