Biological Marker Compounds Research Articles

Organic matter enrichment model of fine-grained rocks in volcanic rift lacustrine basin: A case study of lower submember of second member of Lower Cretaceous Shahezi Formation in Lishu rift depression of Songliao Basin, NE China

Based on sedimentary characteristics of the fine-grained rocks of the lower submember of second member of the Lower Cretaceous Shahezi Formation (K1sh2L) in the Lishu rift depression, combined with methods of organic petrology, analysis of major and trace elements as well as biological marker compound, the enrichment conditions and enrichment model of organic matter in the fine-grained sedimentary rocks in volcanic rift lacustrine basin are investigated. The change of sedimentary paleoenvironment controls the vertical distribution of different lithofacies types in the K1sh2L and divides it into the upper and lower parts. The lower part contains massive siliceous mudstone with bioclast-bearing siliceous mudstone, whereas the upper part is mostly composed of laminated siliceous shale and laminated fine-grained mixed shale. The kerogen types of organic matter in the lower and upper parts are types II2–III and types I–II1, respectively. The organic carbon content in the upper part is higher than that in the lower part generally. The enrichment of organic matter in volcanic rift lacustrine basin is subjected to three favorable conditions. First, continuous enhancement of rifting is the direct factor increasing the paleo-water depth, and the rise of base level leads to the expansion of deep-water mudstone/shale deposition range. Second, relatively strong underwater volcanic eruption and rifting are simultaneous, and such event can provide a lot of nutrients for the lake basin, which is conducive to the bloom of algae, resulting in higher productivity of types I–II1 kerogen. Third, the relatively dry paleoclimate leads to a decrease in input of fresh water and terrestrial materials, including Type III kerogen from terrestrial higher plants, resulting in a water body with higher salinity and anoxic stratification, which is more favorable for preservation of organic matter. The organic matter enrichment model of fine-grained sedimentary rocks of volcanic rift lacustrine basin is established, which is of reference significance to the understanding of the organic matter enrichment mechanism of fine-grained sedimentary rocks of Shahezi Formation in Songliao Basin and even in the northeast China.

Dispersive liquid–liquid microextraction for the analysis of specific marker compounds in human exposed with Polyaromatic hydrocarbons (PAHs)

Occupational exposure of Polyaromatic Hydrocarbons can lead to lipid peroxidation, oxidative stress and kidney function abnormalities. The biological marker compounds associated with these diseases and disorders are present in traces in biological fluids and their quantitative analysis can lead to many clinical applications. Hence, we developed ‘Ultrasound assisted dispersive liquid–liquid microextraction’ for the simultaneous analysis of 6 marker compounds using liquid chromatography mass spectrometry. The developed method is simple to use, rapid and very precise techniques for analyzing biological marker compounds associated with oxidative stress and kidney injury. The factors affecting the extraction efficiency have been optimized using design of experiment. Under the optimized conditions, the proposed method has been validated and the results showed linearity in the range 1–100 ng mL−1 with coefficient of determination (R2) ≥ 0.974–0.989 for all the analytes. The limit of detection and limit of quantification were in the range of 0.002–0.575 ng mL−1 and 0.006–1.898 ng mL−1 respectively with recovery (%) in the range of 94–116 % for all the analytes. The proposed method showed high reproducibility having intra-day and inter-day precision less than 3.21% and 7.31% respectively. We used our validated method to study the effect of PAHs exposure on human, where we analyzed 200 human urine samples obtained from mega kitchen workers. The results suggested that most of the marker compounds were up regulated in the exposed workers than the control one.

Comparative analysis of characteristics and genesis of crude oils of the Zs block in the Tazhong area and the Ha 6 block in the Tabei area, Tarim basin

Ha6 block is located in the north of the Tarim Basin. In this study, the characteristics of the Ordovician crude oil in the Ha6 block were analyzed by the gas chromatography-mass spectrometry (GC-MS) method on the basis of exploration and development data. The results show that C7 compounds are produced by type-I kerogen. According to the comparison, the medium-molecular-weight hydrocarbon fingerprint of the Cambrian crude oil in the Zs block is consistent with that of the Ordovician crude oil in the Ha6 block, which means that their sources are the same. In the two blocks, biological marker compounds of crude oil are also very similar: C27R, C28R, and C29R steranes are in a V-shaped pattern; the Ts/Tm ratio and the content of tricyclic terpanes are both high; and the presence of a large amount of aromatized isoprenoid indicates the crude oil was generated in a strong-reducing environment. In addition, the crude oil single molecule carbon isotope curve is similar with that of Wells Zs1 and Zs5. Therefore, it is comprehensively concluded that the crude oil in the Ordovician reservoirs in the Repu area is mainly supplied by the Cambrian source rock.

Geochemical characteristics and resource potential analysis of Chang 7 organic-rich black shale in the Ordos Basin

AbstractThe Ordos Basin is the largest and most important intracontinental sedimentary depression in China, and a significant amount of crude oil resources has developed within this Mesozoic formation. High-grade organic-rich shale is prevalent in the large-scale areas of the Chang 7 sedimentary stage and provides essential hydrocarbon resources for abundant oil enrichment in the Mesozoic. This research investigated the geochemical characteristics of Chang 7 shale using core samples and well logs and via laboratory tests. In addition, the microscopic components of the shale organic matter (OM), biological marker compounds, carbon isotopes, enrichment grade of trace elements, and elemental ratio were analysed systematically. Moreover, the aspects related to the shale OM source, sedimentary environment and resource potential were evaluated. Our results revealed that spherical alginate and calcium spherical alginate were predominant in the micropetrological components of the shale. Many biomarkers, including n-alkanes, steranes and terpanes, were detected in the gas chromatography – mass spectrometry spectra. An analysis of n-alkanes, regular sterane shapes (C21−/C22− and C26+C27/C28+C29), odd–even predominance index (OEP) and carbon preference index (CPI) values and carbon isotope distributions showed that OM was produced from aquatic organisms. The indicators of trace elements, such as Sr/Ba and V/V+Ni, combined with the biomarker compound in Pr/Ph and the gammacerane index showed the presence of a semi-deep – deep lake environment containing fresh–brackish water. In addition, the hydrocarbon conversion rate index and shale rock pyrolysis parameters revealed that Chang 7 has a high hydrocarbon generation ability and hydrocarbon expulsion efficiency.

Hydrocarbon origin and reservoir forming model research of Longwangmiao Formation, Moxi-Gaoshiti area, Sichuan Basin

Abstract This paper focuses on the Longwangmiao gas reservoir in Moxi-Gaoshiti area, Sichuan Basin. Starting from the tectonic evolution perspective, though comparing biological marker compound and analyzing fluid inclusions, the oil & gas origin and accumulation evolution of Longwangmiao Formation are systematic studied with reference to the burial-thermal evolution of single well geological history in the study area. It is suggested that the oil & gas reservoir is generally characterized by early accumulation, multi-stage filling, late cracking and later adjustment. The oil and gas were mainly sourced from lower Cambrian Qiongzhusi Formation, partly from the Permian source rock. During the geological period, 3 major oil & gas fillings occurred in the Longwangmiao Formation, namely Caledonian-Hercynian filling that was small in scale and produced the first phase of paleo-oil reservoir that soon destroyed by Caledonian movement uplift, large-scale Permian filling that gave rise to the second-phase of paleo-oil reservoir and the Triassic-Jurassic filling that enriched the second phase of paleo-oil reservoir. Finally, the paleo-oil reservoir experienced an in-situ cracking during the cretaceous period that gave rise to a natural gas reservoir and left behind carbonaceous bitumen and oily bitumen in the holes of the Longwangmiao Formation.

An integrated approach to assess the origins of black films on a granite monument

In the present study, samples arising from the scaling of a Portuguese granite building were examined in an attempt to understand the mechanisms of surface blackening and detachment. The building, the Third Order of St. Francis Church, is located in the city centre of Porto which is an area characterised by moderate motor traffic. The Mediterranean climate and the facade orientation favoured the proliferation of microorganisms on the Third Order of St. Francis Church, in Porto. The scientific approach carried out in the South facade revealed that these coloured layers are essentially of biological origin. Subsequent chemical analysis confirmed microscope observations and pointed out to the presence of organic matter synthesised by cyanobacteria, algae and lichens. Numerous biological marker compounds indicated a significant presence of biogenically derived material, suggesting that biological activity was playing a major role in the development of coloured layers and in the detachment processes in this historic building.

Simultaneous Determination of Biological Marker Compounds in Ostericum koreanum by HPLC Method and Discrimination by Principal Component Analysis

An analytical method for the simultaneous determination of four biological marker compounds including bisabolangelone, oxypeucedanin, imperatorin, and isoimperatorin extracted from Ostericum koreanum has been developed by HPLC-UV detection at a wavelength 254 nm. Moreover, biological active compounds have been identified by electrospray ionization tandem mass spectrometry (ESI-MS/MS). In ESI-MS/MS spectra, these compounds produced several characteristic ions through collisional-induced dissociation, enabling to clarify these compounds. HPLC chromatographic separation was successfully achieved with a Develosil RPAQUEOUS C 30 (4.6 × 250 mm, 5 μm) column and a mobile phase of acetonitrile-water (60:40, v/v). This developed analytical method was validated with specificity, selectivity, accuracy and precision. The method was deemed satisfactory by inter- and intra-day validation and exhibited both high accuracy and precision (relative standard deviation < 9.2%). Overall limits of quantitation and detection were approximately 0.03-0.05 μg/mL at a signal-to-noise ratio (S/N) of 3 and were about 0.10-0.25 μg/mL at a S/N of 10. In addition, principal component analysis (PCA) was performed on the analytical data of 14 different Ostericum koreanum samples in order to classify samples collected from different regions. This method has been successfully applied to quality control of Ostericum koreanum extracts.

Organic geochemistry and organic petrology of a potential source rock of early Eocene age in the Beaufort–Mackenzie Basin

The biological marker compounds 17α(H) and 17β(H), 23,28-bisnorlupane have been identified in a coaly interval at about 3300–3320 m depth within the lower Taglu Sequence (early Eocene) in the Immiugak A-06 well in the Beaufort–Mackenzie Basin. These biomarkers were previously only known to occur in the lower part of the Richards Formation and were thus used to infer that the Richards was the source for most of the Tertiary oils and condensates in the basin. The discovery of bisnorlupanes in older, much more organic-rich rocks indicates that the previous oil–source rock correlations may not have been correct and that the coals in the lower Taglu Sequence are likely the dominant effective source rock, especially for the Paleocene and early Eocene reservoirs in the southern part of the Mackenzie Delta. Petrographic and Rock–Eval analyses indicate that the lower Taglu Sequence coaly section should be mainly a source for gas, but with some potential to expel liquids. The level of thermal maturity inferred from Rock–Eval Tmax (432–438 °C, equivalent to about 0.65–0.75% Ro vitrinite) is slightly higher than that inferred from the measured reflectance, fluorescence and foraminiferal colouration index which all indicate that the maturity at 3300 m is about 0.60–0.65% Ro vitrinite equivalent at the Gulf et al. Immiugak A-06 well site.

Assessment of generation temperatures of crude oils

Biological marker maturity parameters were used to estimate the minimum HC generation temperatures of crude oils from Eastern Hungary. More than 50 oils and oil shows were analysed. Molecular- and homologous-ratios of biological marker compounds (triterpanes, steranes, mono- and triaromatic steroid hydrocarbons) were used as maturation parameters. The oils have at least five maturity stages, i.e. they have been generated under different thermal conditions. The highest reservoir temperature in each group was chosen as the best estimate of the groups' temperature just below the generation temperature, i.e. reservoirs of the group might be expected to be at shallower depths (lower temperatures) than those of the generation zone due to vertical migration into pools. For each maturation level, a threshold temperature range for genesis was inferred from reservoir temperatures; they are from 130–135°C for the least mature oils to 210–215°C for the most mature oils. In the least mature oils cracking was not observed, hence carbon–carbon cracking reactions had not taken place during their genesis. The most mature oils are intensively cracked oils; they are almost condensates. Two major genetic groups (families) of oils were found in the area. Both are present in each maturation level. The effects of migration were checked, and no influence on maturation was found. A number of the oils are in overpressured reservoirs within, or just above, the zone of the present-day active oil generation, hence the present-day temperatures of the pools must have been maximum temperatures. Contrary to the traditionally accepted temperature range for petroleum generation–maturation reactions (50–150°C), there is strong evidence from this study that the onset of oil generation requires temperatures higher than 130°C and is still proceeding above 215°C.

Observation of first- and second-order transitions during the heating of Argonne Premium coals

With the recent advent of the ability to separate coal into maceral concentrates of high purity, the individual constituents of coal can now be analyzed separately, without their mutual interference, giving a much better understanding of the macromolecular structure of coal. The sporinites from two Pennsylvanian age coal samples (Illinois Basin, U.S.A.) were studied, one from a vitrinite-rich high-volatile bituminous coal, the other from a liptinite-rich high-volatile butuminous coal of slightly higher rank. Sporinites were isolated from each coal by density gradient centrifugation. The sporinite of the vitrinite-rich coal was compared chemically and petrographically with the parent coal and with the sporinite of the liptinite-rich coal. The fluorescence spectrum of the sporinite from the liptinite-rich coal is shifted to the red end of the spectrum, which may be accounted for by the somewhat higher rank of the sample and/or by differences in the original assemblage of spores. The lack of chemical differences between the extracts of the sporinite and its whole coal reinforce the concept of bitumen as an homogeneous mobile phase pervading the coal. Thus, extract chemistry seems an unsuitable technique for distinguishing between macerals from the same coal. Hopane and sterane distributions in the sporinite and parent coal pyrolyzates are very similar, but the two materials can be readily distinguished by the distribution of tetracyclic diterpanes of the phyllocladane type, which are biological marker compounds derived from higher plant material. Overall, the sporinite is considerably more paraffinic in character and has a greater preponderance of straight-chain alkane moieties than the coal as a whole. In the case of the vitrinite-rich coal, the whole-coal structure appears significantly more polyaromatic than the sporinite. The distributions of thiophenic compounds differ in the pyrolyzates of the two materials. The sporinite from the liptinite-rich coal is even less polycondensed than the sporinite from the vitrinite-rich sample. The chemical and petrographic differences of the two sporinites probably reflect the different assemblages of spores in the original peats and their different diagenetic histories.

A biomarker study of immature crude oils from the Shengli oilfield, People's Republic of China

A suite of crude oils from the Shengli oilfield in northwestern China was subjected to detailed chemical analysis. Crude oils in this suite, believed to be derived from source rocks deposited under fresh, brackish and saline environments have chemical compositions and biological marker compounds indicative of immature source rocks. In this respect the crude oils are unusual, apparently having been formed and expelled from source rocks that have been subjected only to mild thermal stress prior to the main zone of petroleum generation.

The interrelationship of biological marker maturity parameters and molecular yields during contact metamorphism

Jurassic siltstone samples were collected, on a centimetre scale, as a function of increasing distance from a dolerite dyke (Isle of Skye, northwest Scotland). The constant origin and type of the organic matter in this single lithological horizon is indicated by organic petrological observations as well as organic geochemical analyses. Therefore, changes in biological marker distributions, with distance from the dyke contact, can be unequivocally correlated with the thermal influence of the intrusion. The vitrinite reflectance ( R 0 Average) values of these samples increase gradually from 0.35% to 3.60% as the dyke contact is approached. Four classical biological marker maturity parameters ( 20S (20S + 20R) , TA (TA + MA) , C 20 (C 20 + C 28) , and 22S (22S + 22R) ). have been measured from GCMS analyses of the sample extracts. Changes in these molecular parameters were compared with changes in the concentrations of the individual biological marker compounds, expressed relative to mass of rock extracted. This comparison revealed that these molecular parameters are not governed by the conventional productreactant relationships (chiral isomerisation, aromatisation or side-chain cracking reactions) operating solely in the free saturated or aromatic hydrocarbon structures. Release/formation from macromolecular and/or functionalised moieties (hydrocarbon or non-hydrocarbon) followed by compound loss provide an alternative paradigm in all four cases in this particular thermal regime. Direct chiral isomerisation in the free sterane or homohopane cannot, however, be completely ruled out as a contributor to an admixture of processes. Similarly, aromatisation in the free hydrocarbon fraction may account for a proportion of the triaromatic steroids.

An organic geochemical study of bitumens and their potential source rocks from the South Pennine Orefield, Central England

Bitumens associated with PbZn mineralisation hosted by upper Dinantian limestones in the South Pennine Orefield (Derbyshire, Central England) were characterised in terms of maturity as well as source/correlation parameters, and compared with hydrocarbons from the East Midlands oilfield and bitumens from the Cheshire Basin. Potential source rocks from within the Dinantian sequence and from the lower Namurian mudstones of adjacent Carboniferous sedimentary basins were characterised in a similar fashion. The bitumens from both Derbyshire and Cheshire show a range of effects due to biodegradation and water washing, from partial to complete removal of n-alkanes, isoprenoids and polyaromatic hydrocarbons. The bitumen/oil suite (Derbyshire bitumens, Cheshire bitumens and East Midlands oils) show mature biological marker distributions. Whilst the Derbyshire bitumens and East Midlands oils generally correlate well with each other, bitumens from Cheshire show distinct differences. On the grounds of maturity and source/correlation biological marker characteristics, it is possible to suggest likely source rocks for the Derbyshire bitumens and East Midlands oils. Using a “multiparameter approach”, lower Namurian mudstones from the Widmerpool Gulf, along with those from the Gainsborough and Goyt Troughs, are not regarded as source rocks. The lower Namurian mudstones from the Edale Gulf correlated with the East Midlands oils and Derbyshire bitumens on the basis of a restricted number of biological marker compound classes. Bulk and molecular maturity parameters also indicate that these particular formations could have generated hydrocarbons. More local contributions to the Derbyshire bitumens may have been made by some of the organic-rich mudstones within the Dinantian succession.

The Structure of a New C25 Isoprenoid Alkene Biomarker From Diatomaceous Microbial Communities

A new C25 highly branched alkadiene (5) has been isolated from the diatomaceous benthic microbial communities of Hamelin Pool, Western Australia. The structure (5) was determined by detailed n.m.r. and mass spectral analysis, as well as by chemical degradation. Carbon isotopic measurements on this and related isoprenoids were consistent with an origin from diatoms. The role of (5) and related metabolites as biological marker compounds is discussed.

Geochemistry of the Hydrocarbons from the Orinoco Belt: Eastern Venezuela Basin

A regional study has been performed on the heavy crude oils and bitumens from the Orinoco belt in the Eastern Venezuela Basin. The geochemical characterization of these hydrocarbons has been achieved using biological marker compounds including steranes, triterpanes, aromatic steroids and phenantrenes (GC-MS techniques) and petroporphyrins (analyzed by HPLC) as well as general parameters (S.A.R.A. composition, GC results, API gravity, etc.) determined in previous work. The heavy crudes oils and bitumens originated from early mature Cretaceous source rocks located at the North of the basin and are the result of severe biodegradation processes and accumulation in shallow reservoirs. Biodegradation shows different patterns according to the type of location (surface or subsurface). The classification of these hydrocarbons in terms of biodegradation was further complicated by the identification of mixed oils, which include most of the crude oils and bitumens in the Orinoco Belt with API gravities higher than 9-10 API. The crudes and bitumens from the Cerro Negro, Hamaca, and eastern Zuata areas seem to have been generated from the same source, while those of the Machete and western Zuata seem to have been generated from a different source rock. Furthermore, the Machete area oils and bitumens seem to be generatedmore » from source rocks at lower maturity stages.« less

Organic geochemistry of Venezuelan extra-heavy crude oils 2. Molecular assessment of biodegradation

The extent of biodegradation of extra-heavy crude oils from the Eastern Venezuelan basin (Orinoco “Tar” Belt) has been assessed using biological marker compounds which include steranes, triterpanes, aromatic steroids and phenanthrenes (analyzed by GC-MS) and petroporphrins (analyzed by HPLC). The analyses indicate that biodegradation takes place in two regions, namely “surface or close to surface” and “subsurface”, with a different pattern of biodegradation taking place at each type of location. Some oils show patterns of biomarkers which may be the combined result of degradation at both main sites of biodegradation. However, two empirical biodegradation parameters are proposed to achieve this classification. The classification of crude oils in terms of degree of biodegradation is further complicated by the identification of “mixed crudes”.

Comparison of alkanes released from a bituminous coal via hydropyrolysis and low temperature hydrogenation

The use of dispersed sulphided molybdenum catalysts significantly increases the yields of DCM-soluble material from both hydropyrolysis (520 °C) and low temperature (350 °C) hydrogenation of coals. The detailed molecular compositions of the alkanes obtained via hydrogenation and hydropyrolysis with and without catalyst have been determined by g.c.-m.s. for a UK bituminous coal (Gedling). A similar range of compounds was found in each case, but the distributions varied in small, but significant ways. The relative abundance of n-alkanes increases with increasing conversion but maturity parameters based on ratios of hopane and sterane stereoisomers have lower (less mature) values. This is proposed to arise from the catalytic-induced cleavage of weak heteroatom bonds, resulting in the release of biological marker compounds which were incorporated into the macromolecular matrix through functional groups present in the original biolipids and which have retained their original biological configuration.

Geochemistry of Biological Marker Compounds Extracted from Sediments and Oils of the Bulge, Northern Alaska and Yukon Territory

The North Slope is a major petroleum province with production from sediments ranging in age from upper Mississippian through Cretaceous and noncommercial discoveries in sediments from Proterozoic( ) to Tertiary age. Many oils, seeps, and stains, and outcrops are heavily weathered in the Arctic, especially in the Bulge. This severely limits the familiar hydrocarbon-source rock correlations and interpretations based on total organic carbon, pyrolysis data, stable isotopes, and chromatograms of C-15+ extracts. Biological marker compounds such as steranes and triterpanes are present in these extracts in small quantities and are less affected by the severe weathering effects. Despite their horrendous names (both IUPAC and common), gas chromatography-mass spectrometric determined distributions and ratios of these compounds are useful in determining hydrocarbon-source rock relations. Ternary plots of C-27, -28, -29 steranes and rearranged steranes show affinities for depositional environments, possible maturity effects, and source rock-extract correlations. Triterpane analyses show similar correlations and compounds unique to certain stratigraphic units. Comparisons of data from the Arctic National Wildlife Refuge, Prudhoe, National Petroleum Reserve-Alaska, and the Yukon-Beaufort indicate the existence of multiple oil kitchens in the region generating oil and gas.

Aspects of sporinite chemistry

With the recent advent of the ability to separate coal into maceral concentrates of high purity, the individual constituents of coal can now be analyzed separately, without their mutual interference, giving a much better understanding of the macromolecular structure of coal. The sporinites from two Pennsylvanian age coal samples (Illinois Basin, U.S.A.) were studied, one from a vitrinite-rich high-volatile bituminous coal, the other from a liptinite-rich high-volatile butuminous coal of slightly higher rank. Sporinites were isolated from each coal by density gradient centrifugation. The sporinite of the vitrinite-rich coal was compared chemically and petrographically with the parent coal and with the sporinite of the liptinite-rich coal. The fluorescence spectrum of the sporinite from the liptinite-rich coal is shifted to the red end of the spectrum, which may be accounted for by the somewhat higher rank of the sample and/or by differences in the original assemblage of spores. The lack of chemical differences between the extracts of the sporinite and its whole coal reinforce the concept of bitumen as an homogeneous mobile phase pervading the coal. Thus, extract chemistry seems an unsuitable technique for distinguishing between macerals from the same coal. Hopane and sterane distributions in the sporinite and parent coal pyrolyzates are very similar, but the two materials can be readily distinguished by the distribution of tetracyclic diterpanes of the phyllocladane type, which are biological marker compounds derived from higher plant material. Overall, the sporinite is considerably more paraffinic in character and has a greater preponderance of straight-chain alkane moieties than the coal as a whole. In the case of the vitrinite-rich coal, the whole-coal structure appears significantly more polyaromatic than the sporinite. The distributions of thiophenic compounds differ in the pyrolyzates of the two materials. The sporinite from the liptinite-rich coal is even less polycondensed than the sporinite from the vitrinite-rich sample. The chemical and petrographic differences of the two sporinites probably reflect the different assemblages of spores in the original peats and their different diagenetic histories.

Asphaltene-Like Material in Siljan Ring Well Suggests Mineralized Altered Drilling Fluid (includes associated papers 20322 and 20395 )

Summary Black asphaltenic-type material removed from the drillstem at 5945 m [19,505 ft] in Well Gravberg-1 from the Precambrian granite, Siljan, Sweden, was investigated to determine its origin. The chemical characterization showed that this material contains small amounts of hydrocarbons maximizing in the diesel range. No heavy hydrocarbons were identified, except for trace amounts of polycyclic aliphatics. From the chemical and stable isotopic characterizations, we concluded that the black gelatinous material is derived predominantly from the alteration of biodegradable nontoxic lubricant (BNTL) additives by caustic soda, admixed with diesel oil and trace amounts of polycyclic hydrocarbons from recirculating local lake water. No evidence for an indigenous or deep source for the hydrocarbons could be justified. Introduction Well Gravberg-1 was drilled by the Swedish Power Co. (Vattenfall)to test for hydrocarbons in the Siljan Ring meteorite impact crater. The location of the well in the granitic Precambrian Shield of Scandinavia precludes the possibility of finding commercial quantities of hydrocarbons of conventional origin, from the burial and maturation of organic matter in sedimentary basins. However, if methane or other hydrocarbons are migrating into the crust from the mantle, the fractured rocks beneath the Siljan Ring impact site could be a preferred migration pathway in the otherwise impervious granite of the Precambrian Shield. The well has reached a total depth of 6.96 km [4.32 miles], but so far, hydrocarbon gases have been detected only in minor quantities, dissolved in the drilling fluid. On July 11, 1987, during fishing for lost wireline, a sticky, black, mineralized material was recovered on the fishing tools. When the drillpipe was brought to the surface, the interior of the bottom section was filled with about 60 kg [132 Ibm] of the black material. One week before this discovery, a mixture containing one sack of caustic soda, XCD polymer, and 1.1 m3 [7 bbl] of a commercially used BNTL was spotted at the drillbit to free the drillstring, which had stuck at 5945 m [19,505 ft] during a trip from the drilling depth of 6377 m[20.922 ft]. After this addition, fluid was circulated for 1 day, after which the drillpipe became plugged. The nozzles in the drillbit were then closed, and the fluid and additives remained at the formation temperature (∼100 degrees C at ∼6 km [∼212 degrees F at ∼3.7 miles]) until the drillstem was freed 6 days later. Preliminary analysis of the black material established that the major component was magnetite, with smaller amounts of solventsoluble materials, including a suite of straight-chain paraffinic hydrocarbons from C11 to C21, and biological marker compounds very similar to those found in surface hydrocarbon seeps in the vicinity of the Siljan Ring. There was no direct evidence of BNTL in the black material. Using the analysis data, Gold proposed that the black material is the product of a deep subterranean population of bacteria that use abiogenic hydrocarbons migrating up from the mantle. This has been widely reported in the popular and scientific literature as evidence of the validity of the mantle methane hypothesis. We began a detailed analysis of the black material and well additives to determine whether the nonmineral component in the black material might have a less novel origin than Gold suggested and to see whether it may arise from the various chemicals added to the drilling fluid. In particular, geochemical analysis companies frequently caution against misinterpretation of diesel-oil contamination as oil shows. Because of the lack of information in the literature on drilling-mud artifacts, this study represents an opportunity to examine the effects of "drillbit metamorphism" on the production of downhole hydrocarbons. It is particularly well suited because the granite rock contains very small quantities of organic carbon (less than 0.5%) and extractable hydrocarbons. Results and Discussion The black material was analyzed for total organic carbon content, which averaged 11.2% (*0.3%). The remainder consisted of a mineral matrix composed primarily of magnetite. An aqueous extract of the black material analyzed by gas-chromatography/ mass-spectroscopy (GC/MS) was found to contain a complex mixture of fatty acids and fatty-acid derivatives. The black material was extracted with dichloromethane, commonly used to isolate bitumen from source rocks. This extract represented 6.3% of the black material, and the GC (using DB-5 column and flame detector)of the total extract (Fig. 1) is dominated by a single broad peak, eluting between C21 and C22 n-alkanes. There is a subordinate suite of compounds, chromatographially identical to n-alkanes in the C11 to C21 range. The dichloromethane extract was separated by liquid chromatography on a silica-gel column into an aliphatic hydrocarbon fraction (17%), an aromatic hydrocarbon fraction (5%), and a polarcompound fraction (65%). tions JPT P. 1262^