István Dunkl Sedimentology, University of Göttingen

Transcription

1 Beckenanalyse 2: Analytic tools for basin analysis: thermometers and geochronometers [M.Geo.136b] Part 2a: How to measure the paleo-tempearture? (by organic methods) University of Göttingen István Dunkl Sedimentology, University of Göttingen 1) Heat flow in basins 2) Geothermometry in basins by: vitrinite-, bitumen-, graptolite reflectance, Raman spectroscopy, conodont alteration index, spore colour, fluorescence, Rock-Eval, molecular ratios, clay mineralogy... 3) Fission track thermochronology (nuclear physics, statistics) 4) Dating volcanic events (= formation ages) and basement exhumation (= cooling ages) 5) Complex thermal histories of basins & thermal modelling 6) Detrital geochronology (provenance by single-grain ages) 7) (U-Th)/He thermochronology 8) K/Ar, Ar/Ar, Luminescence, ESR and cosmogenic dating of sediments 9) U-Pb and U-series dating of sediments Hydrocarbon fundamental conditions for economic hydrocarbon accumulation SOURCE ROCK mostly fine clay with more than 0.5% kerogene RESERVOIR ROCK porous and permeable as required for production SEAL - CAP ROCK impermeable cover of the reservoir TRAP geometric ordening of source rock /reservoir/seal MATURATION time and temperature CONDUIT permeable migration path from source rock to trap TIMING trap needs to be present at the time of migration

2 ... in this temperature? only the grass grows... Geothermometry - organic-based method groups Optical Chemical Molecular Isotope Geothermometry - inorganic bench-marks Zeolite mineralogy Two-carbonate thermometry Illite smectitite "thermometry" Illite "crystallinity" (IC, Kübler index) b0-parameter Chlorite "crystallinity" Fluid inclusion

3 Thermometry organic bench-marks Vitrinite reflectance (Ro) Vitrinite is a maceral in coal and organic particles derived from land plants since Silurian. With increasing thermal stress, the reflectance value of vitrinite maceral increases. Graptolite reflectance Raman spectroscopy Thermal Alteration Index (TAI) The darkening of kerogen particles with increasing thermal maturity can be used as an indicator of maturity. In order to minimize differences in color caused by changes in the type or thickness of the kerogen particles, TAI measurements are carried out on bisaccate pollen grains whenever possible. If no pollen can be found, TAI values are estimated, with lower confidence, from amorphous kerogen. Conodont Alteration Index (CAI) Colors of the specimens thus obtained are determined under a binocular microscope and compared with standards. Although conodonts are composed of carbonate apatite, changes in conodont color are apparently due to carbonization of inclusions of small amounts of organic matter during catagenesis and metagenesis. Rock eval pyrolysis temperature (T max ) Carbon Preference Index (CPI) Immature rocks often had high CPI values (> 1.5), whereas those of oils were almost always below 1.2. However, the decrease in CPI with increasing maturity depends upon the type of organic matter originally present as well as on maturity. In particular, rocks deposited in pelagic environments, in which the input of terrestrial lipids was very limited, have low CPI values even when immature. Vitrinite in microscope ( w: white light, f: fluorescence ) [Borrego et al., 2006]

4 Optical observation of organic material reflected light transmitted light reflected light UV fluorescence [Diessel, 1992] Ordering and maturation of organic matter [Taylor et al., 1998]

5 Pr inciple Sens itivity a patite 2 38U 1natura lfision decay (Hegas) 0 Te mper ature [ C] He-age e FT-ag zone sensit H eliumorfis iontrackage [Ma] [Wol fetal.,198 Vitrinite Reflectance (%Ro) is a measurement of the percentage of light reflected off the vitrinite maceral in oil immersion. [Bustin et al., 1985] Vertical trend of VR [Taylor et al., 1998]

6 Influence of heat flow on VR trend [Taylor et al., 1998] Primary and recycled vitrinite in a basin fill [Laczó & Jámbor, 1986]

7 VR --- interlaboratory comparison [Borrego et al., 2006] Bias on vitrinite reflectance problem I: anisotropy [Teichmüller & Teichmüller, 1984] [Teichmüller & Teichmüller, 1981]

8 Pr inciple Sens itivity a patite 1natura fision l 2 38U decay (Hegas) 0 [ C] ature mper Te He-age e FT-ag zone sensit H eliumorfis iontrackage [Ma] [Wol fetal., 198 Problems in obtaining true Ro maturities (major maceral types) PROPERLY IDENTIFIED VITRINITE Primary Recycled Caving Mud additives Subtypes vary Ro (<0.5) FACTORS AFFECTING ACCURATE Ro MEASUREMENT Rough textured vitrinite Weathered Partially dissolved (pitted) Fractured Oxidized vitrinite Inclusions Pyrite Bitumen Other macerals Oily vitrinite Natural coking Too few readings (<20) MATERIAL WHICH MAY LOOK LIKE VITRINITE Solid bitumen (several types) Pseudovitrinite Semifusinite [Cardott, 2012] Bias of vitrinite reflectance II: other maceral types [Allen & Allen]

9 Maturation trends of the most common maceral types Reflectance histograms indicating three vitrinite (or maceral!) populations [Nzoussi-Mbassani et al.]

10 Typical vertical trends of organic maturation Change in the trend of vitrinite reflectance? [Teichmüller & Teichmüller, 1968]

11 Typical trends? [Engel and Macko, 1993] Contouered vitrinite reflectance depth profile [Vermeesch et al., 2006]

12 Estimation of the removed sediment thickness [Bray et al., 1992] What was the reason of the increased temperature?? [Bray et al., 1992]

13 Thermometry - vitrinite reflectance [Feinstein et al., 1996] Vitrinite reflectance depth profile Reflectance [%] Depth [km] 100 C/km 70 C/km 50 C/km 40 C/km 30 C/km 20 C/km [Suggate, 1998] [Feinstein et al., 1996]

14 VR depth profiles from the Danish Basin (present day) [Petersen et al., 2008] VR depth profiles (shale sonic velocity corrected depth) [Petersen et al., 2008]

15 Sonic velocity profile (a small excursion towards compaction indicators) [Japsen et al., 2007] Thermometry - vitrinite reflectance vs. Burial diagenesis porosity [Feinstein et al., 1996]

16 A real-life example --- excursion into the oil kitchen (Gulf of Mexico) Vitrinite reflectance Temperature Thermal conductivity Specific heat Time-temperature influence on vitrinite reflectance

17 VR is calibrated principally for diagenetic conditions [Underwood et al., 1993] TTI (an old, but logic method)

18 Principle of subsidence & maturation modelling [Palumbo et al., 1999] What is bitumen? [Quick, 1998]

19 Mean vitrinite vs. bitumen reflectance [Quick, 1998] Geothermometry by bitumen reflectance [Quick, 1998]

20 Geothermometry Bitumen reflectance (can be 'compressively matured solid bitumen') [Gao et al., 2001] Geothermometry by graptolite reflectance [Goodarzi and Norford, 1985]

21 CAI: conodont alteration index [Königshof, 2003] Thermometry - conodont alteration index [Goodarzi and Norford, 1985]

22 Spore colour index [Ibrahim, 1996] Transmitted light vs. UV light excitation of spores [Matchette-Downes, 2009]

23 Vitrinite reflectance (Ro) vs. spore colour index (SCI) [Subroto et al., 2010] Geothermometry (other methods: e.g. fluorescence)

24 Thermometry - fluorescence vs. vitrinite reflectance Fluorescence alteration curves for vitrinites [Pickel et al., 2001]

25 FAMM TM (fluorescence alteration of multiple macerals) [Pickel et al., 2001] FAMM (fluorescence alteration of multiple macerals)!! modification by storage [Pickel et al., 2001]

26 Correlation of various maturation indicators for organic matter [ICCP, Borrego, 2014] Geothermometry - Raman spectroscopy of carbonaceous material [Beyssac et al., 2004]

27 Geothermometry - Raman spectroscopy of carbonaceous material [Beyssac et al., 2004] Geothermometry - Raman spectroscopy of carbonaceous material [Beyssac et al., 2004]

28 Pr inciple Sens itivity a patite 1natura fision l 2 38U decay (Hegas) 0 Pr inciple Sens itivity a patite 1natura fision l 2 38U decay (Hegas) 0 [ C] ature mper Te He-age e FT-ag zone sensit H eliumorfis iontrackage [Ma] [Wol fetal., 198 [ C] ature mper Te He-age e FT-ag zone sensit H eliumorfis iontrackage [Ma] [Wol fetal., 198 Fourier transformation infra red spectroscopy (FTIR) [Lis et al., 2005] Correlation of FTIR parameters and VR [Lis et al., 2005]

29 Pyrolysis Example of rock eval trace. HC = hydrocarbon [ Rock-Eval: distinction of organic and mineral carbon [Behar et al., 2001]

30 Hydrocarbon - maturation [Taylor et al., 1998] Major Rock-Eval parameters [Behar et al., 2001]

31 Major Rock-Eval parameters Tmax is temperature at which maximum yield of hydrocarbons occurs during pyrolysis; S1 is integral of first peak (existing hydrocarbons volatized at 250 C for 5 minutes); S2 is integral of second peak (hydrocarbons produced by pyrolysis of solid organic matter between 250 and 550 C); S3 is integral of third peak (CO2 produced by pyrolysis of kerogen between 250 and 390 C); PI, production index (S1/S1+S2); TOC, total organic carbon; HI, hydrogen index (S2/TOC); OI, oxygen index (S3/TOC) [Nuccio and Condon, 1996 / U.S. GEOLOGICAL SURVEY BULLETIN 2000 O] Calibration of Rock-Eval Tmax to VR [Lee et al., 2010]

32 Pr inciple Sens itivity a patite 1natura fision l 2 38U decay (Hegas) 0 [ C] ature mper Te He-age e FT-ag zone sensit H eliumorfis iontrackage [Ma] [Wol fetal., 198 Maturation estimation by molecular ratios [Taylor et al., 1998] Correlation between optical and hydrocarbon maturity indicators [Matchette-Downes, 2009]

33 Carbon isotope signature as indicator on the transformation temperature [Lüders and Plessen, 2011] Carbon isotope signature as indicator on the transformation temperature [Lüders and Plessen, 2011]