- Email: [email protected]
Petroleum inclusions and residual oils: constraints for deciphering petroleum migration
Journal of Geochemical Exploration 69–70 (2000) 595–599 www.elsevier.nl/locate/jgeoexp
Petroleum inclusions and residual oils: constraints for deciphering petroleum migration H. Volk a,*, U. Mann a, O. Burde a, B. Horsfield a, V. Suchu´ b a
Institute of Petroleum and Organic Geochemistry (ICG-4), Forschungszentrum Ju¨lich, ICG-4 Ju¨lich Germany b Institute of Geology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
Abstract The analysis of petroleum inclusions (PI) in parallel to residual oils ( bitumens) provided specific constraints for petroleum migration processes in the Prague Basin. Whereas organic geochemical information from bitumens is limited due to alteration, additional high quality information was obtained from C1–14-range compounds inside crystals. This was obtained by the application of a closed system for the decrepitation and thermal extraction of PI with subsequent gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). The resulting data not only show pristine live oils, gases, residual and precipitated bitumens and a broad variation of mixtures of the groups above, but also show that gas migration and fractionation processes played a major role in the Prague Basin. 䉷 2000 Elsevier Science B.V. All rights reserved. Keywords: petroleum inclusions; bitumens; migration; fractionation; hydrocarbons; Prague basin
1. Introduction Macroscopically, bitumens represent the only petroleum relics in the basins of a high catagenetic maturity stage. Microscopically visible petroleum inclusions (PI) provide an additional chance to decipher specific processes of petroleum generation and migration. Whereas free petroleum can be altered by evaporative losses, biodegradation or water washing, petroleum trapped in PI retains the composition of fluids at the time of trapping. Additionally, light hydrocarbon information in bitumens is lost and can only be recovered from PI analysis. Offline crushing and leaching of crystals bearing PI is the most frequently used method to analyse high molecular compounds from PI (Karlsen et al., 1993).
* Corresponding author. E-mail address: [email protected] (H. Volk).
However, light hydrocarbons are lost using this ‘crush under solvent’ method. To take this information from PI, a closed system for the decrepitation and thermal extraction of PI coupled with gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) was applied. This system is similar to a system used for the analysis of microscale sealed vessels (MSSV) to determine the kinetic properties of source rocks (Horsfield et al., 1989). So far, only few authors have presented results from similar online crushing analyses (Jochum et al., 1995; Ruble et al., 1998).
2. Geological setting of the Prague Basin The Prague Basin (Barrandian, Czech Republic) represents a classical locality for the Lower and Middle Palaeozoic in Europe. Although no economic hydrocarbon accumulations have been identified,
0375-6742/00/$ - see front matter 䉷 2000 Elsevier Science B.V. All rights reserved. PII: S0375-674 2(00)00074-1
596
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
Fig. 1. Idomorphic quartz crystal occurring as latest phase in a vein crosscutting organic-rich Liten shales (Lower Silurian). Pure aqueous fluid inclusions (A) and inclusions with and oil and water (B) can occur together within one crystal. High molecular portions of petroleum appear as dark rims on the oil phase, fingering into the aqueous phase due to their increased viscosity. A daughter mineral, probably gypsum, points to a salinity ⬎28% NaCl equiv.
some occurrences of bitumens (Jahn, 1883) and PI (Dobes et al., 1997) prove the generation and migration of hydrocarbons. Numerous source rock horizons have been identified in the Prague Basin (Volk et al., 1998). The catagenetic stage of this source rock sequence increases from 0.89% vitrinite reflectance equivalent in the Lower Devonian Zlı´chov Fm. to 2.70% in the Upper Ordovician Letna´ Fm (Francu et al., in preparation). This also means that the uppermost source rock interval has started petroleum generation, as deduced from basin modelling (Mann et al., 1999).
3. Samples and methods Black solid bitumens, as remains of residual oils, are restricted mostly to the Silurian–Devonian boundary sequence built up by the limy Poza´ry and Lochkov formations and were sampled from 17 locations. Bitumen is hosted in the tectonic, subvertical calcite veins and fractures, in fossil moulds (orthoceres, lobolites), beef calcites and within vugs of epigenetic dolomite. In some places, a greenish to orange-brown waxy bitumen occurring as a younger phase can be found together with this black solid bitumen. Crystals bearing PI are often associated with hydrothermal veins in the Prague Basin. In most samples aqueous and PI co-exist and some samples are clearly dominated by PI. The size of PI can reach up to 800 mm. These remarkably big inclusions are visible already in the field to the naked eye. Within one
Fig. 2. Closed system for the decrepitation and themal extraction of petroleum inclusions using a system similar to that used to determine “MSSV-type” kinetics (Horsfield et al. 1989)
inclusion, immiscible water and petroleum may occur (Fig. 1). Bitumens and PI of different paragenetic relationships were analysed separately. Thus, in total, 26 bitumens and 56 PI were characterised microscopically and/or organic-geochemically. Microthermometry was carried out on a Linkam heating–cooling stage. Liquid/vapour ratio, fluorescence and homogenisation temperatures of PI can vary widely within one crystal. Results from microthermometry are discussed elsewhere (Burde, 1999). Bitumen extracts were separated into two hydrocarbon and five hetero-compound fractions. Results from GC and GC-MS measurements including metastable reaction monitoring have been presented elsewhere (Volk et al., 1998, 1999). Here, the results from MSSV-type analysis will be discussed. Samples were cleaned twice in an ultrasonic bath with dichlormethane and purged for 10 min at 200⬚C prior to decrepitation. Hydrocarbon compounds in fluid inclusions were mobilised in a closed system for the decrepitation and thermal extraction of the crystals and analysed using GC and GC–MS. A sketch of this system is shown in Fig. 2. Additionally, high molecular compounds were
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
597
chainlength of n-alkanes 8
group A: 8
group B:
8
group C:
8
16
27 30
pristine live oils with a maximum between n-C 8 and n-C 11 16
27 30
petroleum with a variable maximum between n-C 15 and n-C 20
16
27 30
waxy petroleum with maxima at n-C 18 and n-C 30 and n-alkanes up to n-C 50 16
27 30
group D: waxy petroleum with maximum at n-C 26-28
8
16
27 30
group E: petroleum dominated by gas compounds
Fig. 3. Representative gas chromatograms of the C1–36 range compounds with individual characteristics of petroleum groups A–E from PI. Bitumens show identical distrubutions in the C15⫹-range.
598
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
analysed from crush-under-solvent-extracts for selected samples of the same crystals (32 samples). 4. Composition of n-alkanes of bitumens and petroleum inclusions Although macro- and microscopically bitumens and PI convey the impression of being very different, based on the relative distribution of n-alkanes they group as follows: • Group A (PI only)—maximum concentrations at nC8–11. • Group B (PI and black solid bitumens)—maximum concentration at n-C15–20. • Group C (PI and solid as well as semi liquid bitumens)—maximum concentration at n-C32–34. • Group D (PI and waxy bitumens)—maximum concentration at n-C26–28. • Group E (PI only)—maximum concentrations at nC2–4. In bitumens and PI, we found a nearly complete series of mixtures of the groups above. In addition, most PI contain an admixture of gaseous hydrocarbons (group E). Mixtures result from the trapping of mixed petroleum and/or the trapping of different petroleum within one crystal. Representative examples of the more or less pure end members of this groups are taken from MSSV-type analyses of PI and depicted in Fig. 3. 5. Petroleum generation and migration According to their composition, the analysed samples are interpreted as representatives of three stages of petroleum generation–migration: live oils (A), residual oil from three different phases of migration (B, C and D) and gases (E). Individual petroleum migration phases can be characterised by: (i) residual oils retained in source rocks before primary migration (predominantly C); (ii) residual oils from fractures during secondary migration (predominantly B); and (iii) by precipitates in the centre of fractures due to fractionation processes (D). The very waxy, viscous character of these precipitates probably is due to the presence of dissolved gaseous hydrocarbons as described before from the
Lower Toarcian with the help of a special scanning electron microscopy technique (Cryo-SEM, Mann et al., 1994. This interpretation is in agreement with the geologic conditions in the Prague Basin and the conceptual models for numerical simulations of the thermal evolution (Mann et al., 1999). Due to a more or less complete, 2000 m thick sequence of mature and postmature source rocks, the chances for trapping individual stages of oil (A) and gas (E) formation from different sources—even side by side within the same crystal—had been extremely high. No trends have been observed for the distribution of individual groups as classified above in respect to location or stratigraphy, neither for bitumens nor for PI. This agrees with the fact that there are no carrier rocks within the Prague Basin that would have favoured specific locations and/or stratigraphic units. At the same time, lack of carrier rocks means that the encountered bitumens in fossils and dissolution vugs represent the very last relics of in situ generated petroleum after intensive cracking processes and also some after additional gas flushing (C). The overall predominant occurrence of bitumens and PI in fractures reveals that secondary migration took place along a—probably Late Devonian—fault and fracture system. A migration pathway along faults and fractures is the only possibility where carrier rocks are lacking. Thus, the first phase of secondary migration is represented by residual oils like the variety of black bitumens (B). During a second phase of migration, rapid fluid ascent and pressure decrease caused migrating petroleum to fractionate into gas and condense compounds and to precipitate as the orange waxy bitumens (D).
6. Conclusions The detailed analysis of organic compounds with an improved decrepitation–thermovaporisation system with subsequent gas chromatographic and mass spectrometric analyses of organic compounds in fluid inclusions has yielded the following conclusions: gas migration, gas flushing, migration in gaseous solution and petroleum fractionation represent the predominant processes during petroleum migration in the Prague Basin.
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
Acknowledgements The authors are grateful to Deutsche Forschungsgemeinschaft (DFG) as well as to the co-operation between the Academy of Sciences of the Czech Republic (AS CR) and the Department of International Scientific Relations, DFG. V.S. acknowledges the support by Research Grant A3012703/1997 of AS CR that enabled field works in the Czech Republic. References Burde, O., 1999. Charakterisierung kohlenwasserstoffhaltiger Flu¨ssigkeitseinschlu¨sse aus dem Barrandium des Prager Beckens (Tschechische Republik). Unpublished Master’s thesis, Geol. Univ., Freiburg i.Br. Dobes, P., Suchy´, V., Sedla´ckova´, V., Stanisova´, N., 1997. Hydrocarbon fluid inclusions from fissure quartz: a case study from the Barrandian Basin (Lower Paleozoic). Czech Republic. European Current Research of Fluid Inclusions (ECROFI), Nancy. Francu, E., Mann, U., Volk, H., Herten, U., Kranendonck, O., Maturation of organic matter in the Prague Basin. (in preparation). Horsfield, B., Disko, U., Leistner, F., 1989. The microscale simulation of maturation: outline of a new technique and its potential applications. Geol. Rundschau 78, 361–373. Jahn, J.H., 1883. Einige Bemerkungen u¨ber das bo¨hmische Silur und u¨ber die Bildung des Erdo¨ls. Ver. Geol. Reichsanst. 16, 372–379.
599
Jochum, J., Germann, A., Friedrich, G., Horsfield, B., Pickel, W., 1995. Mechanical decrepitation coupled with gas chromatography—A new method for the determination of hydrocarbons in ore minerals. In: Pasava, J., Kribek, B., Za´k, K. (Eds.). Mineral deposits: From their origin to their environmental impacts. Proceedings of the third biennial SGC meeting. Praha, pp. 757–560. Karlsen, D.A., Nedkvitne, T., Larter, S.R., Bjørlykke, K., 1993. Hydrocarbon composition of authigenic inclusions: application to elucidation of petroleum reservoir filling history. Geochim. Cosmochim. Acta 57, 3641–3659. Mann, U., Neisel, J.D., Burchard, W.-G., Heinen, V., Welte, D.H., 1994. Fluid–rock interfaces as revealed by cryo-scanning electron microscopy. First Break, vol. 12, 6pp. Mann, U., Suchy´, V., Filip, J., Francu, E., Glasmacher, U., Radke, M., Sykorova, I., Volk, H., Wagner, G., Wilkes, H., 1999. Thermal evolution and petroleum generation–migration in the Prague Basin (Barrandian, Czech Republic): an organicgeochemical and basin study. Abstracts 19th International Meeting on Org. Geochem. Istanbul, pp. 207–208. Ruble, T.E., George, S.C., Lisk, M., Quezada, R.A., 1998. Organic compounds trapped in aqueous fluid inclusions. Org. Geochem. 29, 195–205. Volk, H., Wilkes, H., Francu, E., Mann, U., Suchy´, V., Sykorova, I., 1998. Bitumens and petroleum inclusions from the Prague Basin (Barrandian, Czech Republic). Abstracts 6th ALAGO Meeting, Isla Margarita, Venezuela, p. 4. Volk, H., Mann, U., Burde, O., Horsfield, B., Suchy´, V., Wilkes, H., 1999. Bitumens, petroleum inclusions and possible source rocks from the Prague Basin (Barrandian, Czech Republic). Abstract 19th International Meeting on Organic Geochemistry. Istanbul, pp. 205–206.
Petroleum inclusions and residual oils: constraints for deciphering petroleum migration H. Volk a,*, U. Mann a, O. Burde a, B. Horsfield a, V. Suchu´ b a
Institute of Petroleum and Organic Geochemistry (ICG-4), Forschungszentrum Ju¨lich, ICG-4 Ju¨lich Germany b Institute of Geology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
Abstract The analysis of petroleum inclusions (PI) in parallel to residual oils ( bitumens) provided specific constraints for petroleum migration processes in the Prague Basin. Whereas organic geochemical information from bitumens is limited due to alteration, additional high quality information was obtained from C1–14-range compounds inside crystals. This was obtained by the application of a closed system for the decrepitation and thermal extraction of PI with subsequent gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). The resulting data not only show pristine live oils, gases, residual and precipitated bitumens and a broad variation of mixtures of the groups above, but also show that gas migration and fractionation processes played a major role in the Prague Basin. 䉷 2000 Elsevier Science B.V. All rights reserved. Keywords: petroleum inclusions; bitumens; migration; fractionation; hydrocarbons; Prague basin
1. Introduction Macroscopically, bitumens represent the only petroleum relics in the basins of a high catagenetic maturity stage. Microscopically visible petroleum inclusions (PI) provide an additional chance to decipher specific processes of petroleum generation and migration. Whereas free petroleum can be altered by evaporative losses, biodegradation or water washing, petroleum trapped in PI retains the composition of fluids at the time of trapping. Additionally, light hydrocarbon information in bitumens is lost and can only be recovered from PI analysis. Offline crushing and leaching of crystals bearing PI is the most frequently used method to analyse high molecular compounds from PI (Karlsen et al., 1993).
* Corresponding author. E-mail address: [email protected] (H. Volk).
However, light hydrocarbons are lost using this ‘crush under solvent’ method. To take this information from PI, a closed system for the decrepitation and thermal extraction of PI coupled with gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) was applied. This system is similar to a system used for the analysis of microscale sealed vessels (MSSV) to determine the kinetic properties of source rocks (Horsfield et al., 1989). So far, only few authors have presented results from similar online crushing analyses (Jochum et al., 1995; Ruble et al., 1998).
2. Geological setting of the Prague Basin The Prague Basin (Barrandian, Czech Republic) represents a classical locality for the Lower and Middle Palaeozoic in Europe. Although no economic hydrocarbon accumulations have been identified,
0375-6742/00/$ - see front matter 䉷 2000 Elsevier Science B.V. All rights reserved. PII: S0375-674 2(00)00074-1
596
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
Fig. 1. Idomorphic quartz crystal occurring as latest phase in a vein crosscutting organic-rich Liten shales (Lower Silurian). Pure aqueous fluid inclusions (A) and inclusions with and oil and water (B) can occur together within one crystal. High molecular portions of petroleum appear as dark rims on the oil phase, fingering into the aqueous phase due to their increased viscosity. A daughter mineral, probably gypsum, points to a salinity ⬎28% NaCl equiv.
some occurrences of bitumens (Jahn, 1883) and PI (Dobes et al., 1997) prove the generation and migration of hydrocarbons. Numerous source rock horizons have been identified in the Prague Basin (Volk et al., 1998). The catagenetic stage of this source rock sequence increases from 0.89% vitrinite reflectance equivalent in the Lower Devonian Zlı´chov Fm. to 2.70% in the Upper Ordovician Letna´ Fm (Francu et al., in preparation). This also means that the uppermost source rock interval has started petroleum generation, as deduced from basin modelling (Mann et al., 1999).
3. Samples and methods Black solid bitumens, as remains of residual oils, are restricted mostly to the Silurian–Devonian boundary sequence built up by the limy Poza´ry and Lochkov formations and were sampled from 17 locations. Bitumen is hosted in the tectonic, subvertical calcite veins and fractures, in fossil moulds (orthoceres, lobolites), beef calcites and within vugs of epigenetic dolomite. In some places, a greenish to orange-brown waxy bitumen occurring as a younger phase can be found together with this black solid bitumen. Crystals bearing PI are often associated with hydrothermal veins in the Prague Basin. In most samples aqueous and PI co-exist and some samples are clearly dominated by PI. The size of PI can reach up to 800 mm. These remarkably big inclusions are visible already in the field to the naked eye. Within one
Fig. 2. Closed system for the decrepitation and themal extraction of petroleum inclusions using a system similar to that used to determine “MSSV-type” kinetics (Horsfield et al. 1989)
inclusion, immiscible water and petroleum may occur (Fig. 1). Bitumens and PI of different paragenetic relationships were analysed separately. Thus, in total, 26 bitumens and 56 PI were characterised microscopically and/or organic-geochemically. Microthermometry was carried out on a Linkam heating–cooling stage. Liquid/vapour ratio, fluorescence and homogenisation temperatures of PI can vary widely within one crystal. Results from microthermometry are discussed elsewhere (Burde, 1999). Bitumen extracts were separated into two hydrocarbon and five hetero-compound fractions. Results from GC and GC-MS measurements including metastable reaction monitoring have been presented elsewhere (Volk et al., 1998, 1999). Here, the results from MSSV-type analysis will be discussed. Samples were cleaned twice in an ultrasonic bath with dichlormethane and purged for 10 min at 200⬚C prior to decrepitation. Hydrocarbon compounds in fluid inclusions were mobilised in a closed system for the decrepitation and thermal extraction of the crystals and analysed using GC and GC–MS. A sketch of this system is shown in Fig. 2. Additionally, high molecular compounds were
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
597
chainlength of n-alkanes 8
group A: 8
group B:
8
group C:
8
16
27 30
pristine live oils with a maximum between n-C 8 and n-C 11 16
27 30
petroleum with a variable maximum between n-C 15 and n-C 20
16
27 30
waxy petroleum with maxima at n-C 18 and n-C 30 and n-alkanes up to n-C 50 16
27 30
group D: waxy petroleum with maximum at n-C 26-28
8
16
27 30
group E: petroleum dominated by gas compounds
Fig. 3. Representative gas chromatograms of the C1–36 range compounds with individual characteristics of petroleum groups A–E from PI. Bitumens show identical distrubutions in the C15⫹-range.
598
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
analysed from crush-under-solvent-extracts for selected samples of the same crystals (32 samples). 4. Composition of n-alkanes of bitumens and petroleum inclusions Although macro- and microscopically bitumens and PI convey the impression of being very different, based on the relative distribution of n-alkanes they group as follows: • Group A (PI only)—maximum concentrations at nC8–11. • Group B (PI and black solid bitumens)—maximum concentration at n-C15–20. • Group C (PI and solid as well as semi liquid bitumens)—maximum concentration at n-C32–34. • Group D (PI and waxy bitumens)—maximum concentration at n-C26–28. • Group E (PI only)—maximum concentrations at nC2–4. In bitumens and PI, we found a nearly complete series of mixtures of the groups above. In addition, most PI contain an admixture of gaseous hydrocarbons (group E). Mixtures result from the trapping of mixed petroleum and/or the trapping of different petroleum within one crystal. Representative examples of the more or less pure end members of this groups are taken from MSSV-type analyses of PI and depicted in Fig. 3. 5. Petroleum generation and migration According to their composition, the analysed samples are interpreted as representatives of three stages of petroleum generation–migration: live oils (A), residual oil from three different phases of migration (B, C and D) and gases (E). Individual petroleum migration phases can be characterised by: (i) residual oils retained in source rocks before primary migration (predominantly C); (ii) residual oils from fractures during secondary migration (predominantly B); and (iii) by precipitates in the centre of fractures due to fractionation processes (D). The very waxy, viscous character of these precipitates probably is due to the presence of dissolved gaseous hydrocarbons as described before from the
Lower Toarcian with the help of a special scanning electron microscopy technique (Cryo-SEM, Mann et al., 1994. This interpretation is in agreement with the geologic conditions in the Prague Basin and the conceptual models for numerical simulations of the thermal evolution (Mann et al., 1999). Due to a more or less complete, 2000 m thick sequence of mature and postmature source rocks, the chances for trapping individual stages of oil (A) and gas (E) formation from different sources—even side by side within the same crystal—had been extremely high. No trends have been observed for the distribution of individual groups as classified above in respect to location or stratigraphy, neither for bitumens nor for PI. This agrees with the fact that there are no carrier rocks within the Prague Basin that would have favoured specific locations and/or stratigraphic units. At the same time, lack of carrier rocks means that the encountered bitumens in fossils and dissolution vugs represent the very last relics of in situ generated petroleum after intensive cracking processes and also some after additional gas flushing (C). The overall predominant occurrence of bitumens and PI in fractures reveals that secondary migration took place along a—probably Late Devonian—fault and fracture system. A migration pathway along faults and fractures is the only possibility where carrier rocks are lacking. Thus, the first phase of secondary migration is represented by residual oils like the variety of black bitumens (B). During a second phase of migration, rapid fluid ascent and pressure decrease caused migrating petroleum to fractionate into gas and condense compounds and to precipitate as the orange waxy bitumens (D).
6. Conclusions The detailed analysis of organic compounds with an improved decrepitation–thermovaporisation system with subsequent gas chromatographic and mass spectrometric analyses of organic compounds in fluid inclusions has yielded the following conclusions: gas migration, gas flushing, migration in gaseous solution and petroleum fractionation represent the predominant processes during petroleum migration in the Prague Basin.
H. Volk et al. / Journal of Geochemical Exploration 69–70 (2000) 595–599
Acknowledgements The authors are grateful to Deutsche Forschungsgemeinschaft (DFG) as well as to the co-operation between the Academy of Sciences of the Czech Republic (AS CR) and the Department of International Scientific Relations, DFG. V.S. acknowledges the support by Research Grant A3012703/1997 of AS CR that enabled field works in the Czech Republic. References Burde, O., 1999. Charakterisierung kohlenwasserstoffhaltiger Flu¨ssigkeitseinschlu¨sse aus dem Barrandium des Prager Beckens (Tschechische Republik). Unpublished Master’s thesis, Geol. Univ., Freiburg i.Br. Dobes, P., Suchy´, V., Sedla´ckova´, V., Stanisova´, N., 1997. Hydrocarbon fluid inclusions from fissure quartz: a case study from the Barrandian Basin (Lower Paleozoic). Czech Republic. European Current Research of Fluid Inclusions (ECROFI), Nancy. Francu, E., Mann, U., Volk, H., Herten, U., Kranendonck, O., Maturation of organic matter in the Prague Basin. (in preparation). Horsfield, B., Disko, U., Leistner, F., 1989. The microscale simulation of maturation: outline of a new technique and its potential applications. Geol. Rundschau 78, 361–373. Jahn, J.H., 1883. Einige Bemerkungen u¨ber das bo¨hmische Silur und u¨ber die Bildung des Erdo¨ls. Ver. Geol. Reichsanst. 16, 372–379.
599
Jochum, J., Germann, A., Friedrich, G., Horsfield, B., Pickel, W., 1995. Mechanical decrepitation coupled with gas chromatography—A new method for the determination of hydrocarbons in ore minerals. In: Pasava, J., Kribek, B., Za´k, K. (Eds.). Mineral deposits: From their origin to their environmental impacts. Proceedings of the third biennial SGC meeting. Praha, pp. 757–560. Karlsen, D.A., Nedkvitne, T., Larter, S.R., Bjørlykke, K., 1993. Hydrocarbon composition of authigenic inclusions: application to elucidation of petroleum reservoir filling history. Geochim. Cosmochim. Acta 57, 3641–3659. Mann, U., Neisel, J.D., Burchard, W.-G., Heinen, V., Welte, D.H., 1994. Fluid–rock interfaces as revealed by cryo-scanning electron microscopy. First Break, vol. 12, 6pp. Mann, U., Suchy´, V., Filip, J., Francu, E., Glasmacher, U., Radke, M., Sykorova, I., Volk, H., Wagner, G., Wilkes, H., 1999. Thermal evolution and petroleum generation–migration in the Prague Basin (Barrandian, Czech Republic): an organicgeochemical and basin study. Abstracts 19th International Meeting on Org. Geochem. Istanbul, pp. 207–208. Ruble, T.E., George, S.C., Lisk, M., Quezada, R.A., 1998. Organic compounds trapped in aqueous fluid inclusions. Org. Geochem. 29, 195–205. Volk, H., Wilkes, H., Francu, E., Mann, U., Suchy´, V., Sykorova, I., 1998. Bitumens and petroleum inclusions from the Prague Basin (Barrandian, Czech Republic). Abstracts 6th ALAGO Meeting, Isla Margarita, Venezuela, p. 4. Volk, H., Mann, U., Burde, O., Horsfield, B., Suchy´, V., Wilkes, H., 1999. Bitumens, petroleum inclusions and possible source rocks from the Prague Basin (Barrandian, Czech Republic). Abstract 19th International Meeting on Organic Geochemistry. Istanbul, pp. 205–206.