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Organic geochemical characteristics of Miocene oil shale deposits in the Eskisehir Basin, Western Anatolia, Turkey.

1. Introduction

Turkey hosts 1.6 billion tonnes of oil shale reserves. Some of the most important oil shale deposits are located in Beypazari (Ankara), Seyitomer (Kutahya), Himmetoglu and Hatildag (Bolu), Golpazari (Bilecik), Ulukusla (Nigde), Burhaniye (Balikesir), Beydili (Ankara), Dodurga (Corum) and Bahqecik (Izmit) regions. Geologic characteristics, organic and trace element geochemistry, chemical and thermal properties and economic value of the oil shales from these areas have been investigated in several studies [1-11].

In addition to the above-mentioned fields, an oil shale deposit was discovered during coal exploration initiated by the General Directorate of Mineral Research and Exploration (MTA) in 2008 in the Eskisehir Basin, western Turkey. In this basin, 350 boreholes were drilled for coal exploration and reserve improvement and about 1.5 billion tonnes of sub-bituminous coal and about 1 billion tonnes of oil shale reserve were discovered. The thickness of oil shale is between 5 and 60 m with an average of 20-30 m. Oil shale encountered in the basin is thin-layered and laminated, and light brown, gray and blackish in color.

In this contribution, the organic geochemical characteristics, thermal maturity, depositional environment and conditions as well as source rock potential of the oil shale discovered in the Eskisehir Basin are investigated.

2. Geological setting

The study area is located in the Eskisehir graben east of Eskisehir in western Anatolia, Turkey (Fig. 1). Regional geological work was first carried out by Siyako et al. [12], Gozler et al. [13] and Senguler [16], followed by coal and oil shale studies by other researchers [14-15]. The basement of the region is composed of Paleozoic metamorphosed rocks and Mesozoic ophiolites. The metamorphic rocks are in tectonic contact with ophiolitic units in the northern part of the basin [13]. The metamorphic rocks consist of schist and marbles and ophiolitic melange represented by radiolarite-bearing limestone, mudstone, serpentinite, diabase, limestone and gabbro.

The basement rocks are unconformably overlain by Miocene deposits which are developed in three different facies: m1, m2 and m3 series (Fig. 2). The m1 series at the base of the Miocene sequence is composed mainly of sandstone and clay stone. Pebbles of conglomerate have been derived from the basement rocks of various types. The upper portion of the m1 series is a red, yellowish grey, gray, light gray but mostly brownish red thick to very thick bedded sandstone-claystone sequence [12].

This sequence is overlain by the m2 series which is, from bottom to top, composed of alternating, partly pebbly green claystone, coal, gray sandstone, dark gray-green siltstone, oil shale, claystone, coal and green claystone-sandstone fine-grained conglomerate. The sequence is mostly green and yellow in color and partly multicolored. The lower levels of thin-bedded claystone and marls are reddish and purplish and change to green to the top. Yellow parts are generally the upper levels of claystone and marls. Very thin bedded limestone bands occur between marls and clays. North of Sevinc-Agapinar coal and oil shale are found at depths between 250 and 450 m. In deeper parts of the basin the thickness of the m2 series is 350-600 m; however, in the study area its thickness reaches 400 m [16]. The upper parts of the Miocene sequence comprise the m3 series, which consists of limestone and conglomerate. Limestone is pale white and gray in color and occurs as lenses. In the study area, this unit has a thickness of 30-40 m.

Palynological analysis of the samples collected from the lower and upper levels of coal zones show that the coal and oil shale-bearing unit (m2) was deposited in the Lower-Middle Miocene. The amount of various forest trees and swamp-freshwater plants is high whilst river-side and open field plants are in low quantity. Bortyococcus ovoidites forms detected in the unit are in support of freshwater conditions. Palynological data indicate that the coal and oil shale-bearing unit in the Eskisehir graben was deposited under wet and hot conditions [17].

Pliocene deposits in the basin are composed of pale, light brown claystone and loosely compacted conglomerate. Conglomerate levels in the m3 series contain pebbles of all units older than conglomerate itself. This unit has a thickness of 15-25 m. Quaternary alluvium, modern deposits and slope wash unconformably cover all the underlying deposits.

3. Material and methods

In the current study, boreholes 37, 52 and 53 drilled in the central part of the basin (north of Agapinar village) cut 20-30 m thick oil shale in the deeper sections of the Eskisehir Basin. The distance between boreholes 37-52 was 1 km, between boreholes 37-53 1.5 km and between boreholes 52-53 600 m. In borehole 37, 355 m claystone, siltstone, sandstone and conglomerate, 20 m oil shale (between 355 and 378 meters) and 20 m coal were cut and the borehole was completed at a depth of 410 m. In borehole 52, 295 m claystone, siltstone, sandstone and conglomerate, 25 m oil shale (between 295 and 321 meters), 10 m coal and 10 m claystone were cut and the borehole was completed at a depth of 340 m. In borehole 53, 355 m claystone, siltstone, sandstone and conglomerate, 25 m coal, 30 m oil shale (between 353 and 378 meters) and 10 m coal were cut and the borehole was completed at a depth of 430 m (Fig. 3).

Pyrolysis and TOC analyses were performed for 14, 15 and 16 samples selected respectively from boreholes 37, 52 and 53 drilled in the Eskisehir Basin. From borehole 37, one coal sample, one coaliferous claystone sample and 12 oil shale samples were taken. Two coal and 13 oil shale samples were collected from borehole 52. From borehole 53, three were coal samples and 13 oil shale samples (Tables 1, 2 and 3).

Rock-Eval pyrolysis and TOC analyses of all the samples were made using a Rock-Eval 6 instrument equipped with a TOC module. The samples were heated from 300[degrees]C (hold time 3 min) to 650[degrees]C at 25[degrees]C/min. The crushed rock was heated from 400[degrees]C (hold time 3 min) to 850[degrees]C (hold time 5 min) at 25[degrees]C/min for oxidation. Following Rock-Eval, TOC analysis, gas chromatographic (GC) (bulk extract) and gas chromatographic-mass spectrometric (GC-MS) (saturated hydrocarbons sterane and terpane) analyses of extracts obtained from three samples (37-9, 52-12, 53-9) were conducted.

The [C.sub.15+] soluble organic matter (SOM) was isolated following Soxhlet extraction (40 hr) of the powdered rock with dichloromethane ([C.sub.H2][C.sub.l2]). Whole rock extracts were analysed using a Varian 3400 gas chromatograph equipped with flame photometric (FPD) and flame ionisation detectors (FID). A fused capillary column (60 m, 0.20 mm i.d.) coated with cross-linked dimethylpolysiloxane (J&W, 0.25 pm film thickness) was used. Helium was the carrier gas. The oven temperature was programmed from 40[degrees]C (hold time 8 min) to 270[degrees]C (hold time 60 min) at 4[degrees]C/min.

The oil shale extracts were deasphaltened using n-pentane and fractionated by thin-layer chromatography (MK-Iatroscan). n-Hexane, toluene and methanol were used for separation of extracts into saturated hydrocarbons, aromatic hydrocarbons and NSO fractions, respectively. GC-MS analyses of saturated fractions were performed using an Agilent 5975C quadrupole mass spectrometer coupled to a 7890A gas chromatograph and a 7683B automatic liquid sampler. The gas chromatograph was equipped with an HP-1MS fused silica capillary column of 60 m length, 0.25 mm i.d. and 0.25 pm film thickness. Helium was used as the carrier gas. The oven temperature was programmed from 50[degrees]C (hold time 10 min) to 200[degrees]C (hold time 15 min) at 10[degrees]C/min, to 250[degrees]C (hold time 24 min) at 5[degrees]C/min and then to 280[degrees]C (hold time 24 min) at 2[degrees]C/min. Finally, the oven temperature was increased to 290[degrees]C (hold time 40 min) at 1[degrees]C/min. The mass spectrometer was operated in EI mode at an ionisation energy of 70 eV and a source temperature of 300[degrees]C. The biomarker contents were determined using single ion recording at m/z 191 (190.7-191.7) for terpanes and tricyclic triterpanes, and at m/z 217 (216.7-217.7) for steranes and rearranged steranes. Compounds were identified by their retention time and elution order matching.

4. Results

4.1. TOC and pyrolysis analyses

Pyrolysis and TOC values of oil shale and coal samples from boreholes 37, 52 and 53 are given in Tables 1, 2 and 3. TOC values of oil shale samples from boreholes 37, 52 and 53 are 6.39-37.15% wt., 6.32-20.22% wt. and 6.87-14.46% wt., respectively (Tables 1, 2 and 3; Fig. 4a). The oil shale samples from these boreholes have very low [S.sub.1] (0.35-2.78 mg HC/g rock) and very high [S.sub.2] (34.60-158.25 mg HC/g rock) values as it is common for oil shale. In general, the Eskisehir oil shale is characterised by high to very high HI (392-777 mg HC/g rock) (Fig. 4b) and low OI (13-92 mg C[O.sub.2]/g TOC) values (Tables 1, 2 and 3). In the oil shale samples, [S.sub.2]/[S.sub.3] values are quite high (5.49-56.79) but in coal samples, very low (1.55-4.23). The residual carbon value is also high (21.32-47.84%) in coal and coal bearing claystone samples and low (3.16-7.97%, except one sample) in oil shale samples. Coal and coaliferous clay samples are distinguished from oil shale samples by their very high [S.sub.3] (13.69-26.94 mg C[O.sub.2]/g rock) and low HI (59-184 mg HC/g rock) values. All the samples are characterized by very low PI (0.01-0.05), but very high PY (23.72-159.32 mg HC/g rock) values (Tables 1, 2 and 3).

Almost all oil shale samples with high HI values are plotted in Type II kerogen area which is close to Type I kerogen area, and only a few samples are found within the Type I kerogen field. Coal and claystone samples are within the Type II-Type III kerogen field (Figs. 5a-b). All the oil shale samples with high [S.sub.2] and TOC values show excellent source rock characteristics (Fig. 6).

4.2. Molecular compounds

4.2.1. n-Alkanes and isoprenoids

On the gas chromatograms of oil shale samples, n-alkanes are more abundant than isoprenoids (Fig. 7). Pr/n-[C.sub.17] and Ph/n-[C.sub.18] ratios are very low (Table 4). n-Alkanes are more dominant than neighboring isoprenoids and only in one sample Pr is slightly more predominant than n-[C.sub.17]. For all oil shale samples phytane (Ph) is more dominant than pristane (Pr) and Pr/Ph ratios are between 0.17 and 0.96 (Fig. 7; Table 4). On the gas chromatograms oil shale samples show high peaks in the biomarker area (Fig. 7).

4.2.2. Steranes and terpanes

On m/z 217 mass chromatograms pregnanes were recorded in all the oil shale samples. These compounds are quite abundant in one sample from borehole 37, low in one sample from borehole 52 and moderately abundant in one sample from borehole 53 (Fig. 8). Diasteranes were recorded in low quantities in three oil shale samples. The diasterane/sterane ratio was calculated to be very low (0.42-0.14) (Table 5). For all the oil shale samples n-steranes are more abundant than iso- and diasteranes. 20S/(20S + 20R) and [beta][beta]/([beta][beta] + [alpha][alpha]) [C.sub.29] sterane ratios were computed to be very low (0.46-0.18 and 0.14-0.04, respectively) (Table 5).

On m/z 191 mass chromatograms [C.sub.19]-[C.sub.29] tricyclic terpanes were recorded in very low abundance and in this range [C.sub.23] is the dominant tricyclic terpane (Fig. 9). Contrary to low-numbered tricyclic terpanes, [C.sub.30] tricyclic terpane (S + R) was measured in high concentrations, being a major component on the m/z 191 mass chromatogram. Ts was recorded in trace quantities whilst Tm in high concentrations. The concentrations of [C.sub.29] norhopane and [C.sub.30] hopane are generally low and [C.sub.29] norhopane is slightly dominant over [C.sub.30] hopane. [C.sub.30] norhopane was recorded in high concentrations in two samples and in low quantity in one sample. In all the oil shale samples the homomoretane abundance is quite high, whilst that of homohopanes is low. Only the [C.sub.31] homohopane abundance is slightly higher and high-numbered homohopanes are either present in trace amounts or their existence was never recorded (Fig. 9). 22R homohopanes are more abundant than 22S epimers and the 22S/(22S + 22R) homohopane ratio of oil shale samples is very low (Table 6).

5. Discussion

The TOC content of oil shale in the Eskisehir Basin is high to very high (Tables 1, 2 and 3), ranging from 6.32 to 37.15% wt. TOC consists mostly of pyrolysable carbon and shows correspondingly high PY values (35.50159.32 mg HC/g rock), which implies that the Eskisehir oil shale has quite high hydrocarbon generation potential (Tables 1, 2 and 3). HI values of oil shale samples from all boreholes are relatively high (392-777 mg HC/g TOC) and the [S.sub.2]/[S.sub.3] ratio, which defines the type of organic matter and the variety of hydrocarbon to be derived, was computed to be high as well (5.99-56.79). High HI and [S.sub.2]/[S.sub.3] values and the dominant Type II (to a lesser degree, Type I) kerogen indicate that when exposed to excessive temperature, the organic matter in the Eskisehir oil shale can generate a significant amount of oil.

The Pr/Ph ratio of oil shale samples from boreholes 37, 52 and 53 is rather low (0.17-0.96) showing that oil shale was deposited under anoxic conditions. Palynological analysis of oil shale and coal performed by Senguler et al. [17] indicates that the oil shale and coal were deposited in a freshwater swamp and lacustrine environment when the climate was predominantly humid and hot. On the m/z 191 mass chromatograms of oil shale samples, gammacerane, which is indicative of salinity [18-22], is practically absent, implying that the environment was of a freshwater type.

Low sterane concentrations and low regular sterane/hopane ratio suggest terrigenous or microbial reworked organic matter [23]. According to Moldowan et al. [24], the sterane/hopane ratio in oils derived from nonmarine sources is lower than that of marine sources. In the oil shale samples from all the boreholes, both the sterane abundance and sterane/hopane ratio are very low (0.08-0.20) (Fig. 8; Table 5). On the m/z 191 mass chromatograms of oil shale samples, no oleanane was recorded, which also supports terrigenous organic matter input [25-30] (Fig. 9). Typically, [C.sub.27] sterane is a major component in lacustrine source rock or oils [19]. Indeed, [C.sub.27] is dominant in the oil shale samples from boreholes 37 and 53 whilst C28 sterane is prevailing in those from borehole 52. On the other hand, [C.sub.29] sterane which also reflects terrigenous organic matter input [19] was recorded in low quantities in all samples (Table 5). Moreover, the low tricyclic terpane abundance (except for [C.sub.30]), and low (CJ9 + C20)/C23 tricyclic terpane ratio show that terrigenous organic matter is almost absent (Fig. 9; Table 6). For all the samples [C.sub.30] tricyclic terpane (S + R) was recorded in a surprisingly high abundance and is the most prevailing component as revealed on the m/z 191 mass chromatogram. Ourisson et al. [31] state that tricyclic terpanes were derived from prokaryotic membranes. In addition, high tricyclic terpane concentrations are indicative of algae in tasmanite-rich rocks deposited at high paleo-latitudes [32-34]. The unusually high [C.sub.30] tricyclic terpane concentrations in the Eskisehir oil shale which was deposited in a lacustrine environment might be related to a high algal contribution to organic matter. In the shale Senguler et al. [17] found Bortyococcus ovoidites forms which are indicative of a freshwater environment and in this respect, [C.sub.30] tricyclic terpane abundance may have been derived from these algae.

Contrary to our expectations, the investigated oil shale samples show high [C.sub.29]/[C.sub.30] hopane and [C.sub.31]R homohopane/[C.sub.30] hopane ratios (Fig. 9; Table 6). The high [C.sub.29]/[C.sub.30] hopane ratio is suggested to be an indicator of carbonate presence, being especially characteristic of carbonate-rich rocks and oils [22, 35, 36]. Considering that oil shale has very low carbonate content, the high value of this ratio is confusing. The [C.sub.31]R homohopane/[C.sub.30] hopane ratio is also used to discriminate between the lacustrine and marine environments and its value < 0.25 is suggested to be typical of lacustrine deposits [22]. Although geological data indicate that the Eskisehir oil shale was deposited in the lacustrine environment, this ratio is quite high (1.69-2.45), which is in conflict with geological interpretation (Table 6).

Ts/(Ts + Tm) and diasterane/sterane ratios are affected by both maturity and lithology of source rock. It was shown that these two parameters are increased with increasing maturity [20, 19, 36]. Furthermore, the ratio of these two biomarkers tends to be higher in clay-rich source rocks and oils derived from these rocks in comparison with that in carbonate units [19, 20, 36]. Although oil shale has a high clay content, these two ratios are found to be very low in it (Table 6). Low Ts/(Ts+Tm) and diasterane/sterane ratios in oil shale are in contradiction with its lithology but are consistent with its low maturity level.

[T.sub.max] values of oil shale samples from boreholes 37, 52 and 53 are between 421 and 435[degrees]C, indicating that the rock is immature and did not enter into the oil window. Very low PI values of oil shale (0.01-0.05) also demonstrate its low maturity level and the very low rate of transformation of kerogen to hydrocarbon. On the gas chromatograms of oil shale samples from boreholes 37, 52 and 53, peaks with high concentrations particularly in the biomarker area are indicative of an immature character of organic matter [19]. 20S/(20S + 20R) and [beta][beta]/([beta][beta] + [alpha][alpha]) sterane and 22S/(22S + 22R) homohopane ratios are used for analyzing the maturity of oil and source rock [19, 20, 36, 37]. The 22S/(22S + 22R) homohopane ratio of about 0.60 attains equilibrium at the beginning of the oil window [36]. 20S/(20S + 20R) and [beta][beta]/([beta][beta] + [alpha][alpha]) sterane ratios of 0.55 and 0.70, respectively, attain equilibrium after a maturity level at which oil generation is maximum [37]. Very low 20S/(20S + 20R) and PP/(PP + aa) sterane (for [C.sub.29]) and 22S/(22S + 22R) homohopane (for [C.sub.32]) ratios of oil shale indicate that it has not reached oil generation maturity. The moretane/hopane ratio is decreased with increasing maturity and it is an indicator of immature-early oil generation stages for oil and source rocks [22, 36, 38-40]. This ratio was computed to be very high for oil shale samples (0.52-1.28), implying an immature source rock. It has been suggested in several studies that [C.sub.29]Ts is more stable to maturity in comparison with [C.sub.29] norhopane and the [C.sub.29]Ts/([C.sub.29]Ts + [C.sub.29] H) ratio is increased with increasing maturity [41-45]. For oil shale samples this ratio is very low (0-0.35). Pyrolysis and biomarker data about oil shale samples from the study-area boreholes show that the shale levels cut in these boreholes are generally of similar maturity.

6. Conclusions

The very high values of TOC (6.32-37.15% wt.), PY ([S.sub.1] + [S.sub.2]) (35.50-159.32 mg HC/g rock) and Hydrogen Index (392-777 mg HC/g TOC) of the Eskisehir Basin oil shale show its excellent source rock characteristics and high hydrocarbon generation potential. Oil shale samples with dominantly Type II and, to a lesser extent, Type I kerogen are characterised by organic matter with oil generation potential.

The extremely low Pr/Ph ratio implies that lacustrine shale was deposited under anoxic conditions. Based on biomarker data, the Eskisehir oil shale is characterized chiefly by algal and bacterial organic matter with scarce terrigenous organic matter input.

The very low [T.sub.max] and Production Index values of oil shale samples reflect immature organic matter content. Biomarker data also indicate that oil shale contains organic matter with low maturity level (immature). Results of TOC and pyrolysis analysis and biomarker data imply that although the Eskisehir oil shale has a high hydrocarbon potential and oil generation capacity, it has not experienced any hydrocarbon generation due to not having attained sufficient burial and thermal maturity.

doi: 10.3176/oil.2014.4.02

Acknowledgements

The authors would like to thank the Research Foundation of Karadeniz Technical University (KTU) and the Geochemical Laboratory of the Turkish Petroleum Co. (TPAO) for their support in analyzing the data and the General Directorate of Mineral Research and Exploration (MTA) for their support in field studies and sampling. This study benefitted from guidance by Senior Geologist Y. H. iztan (TPAO). The authors thank anonymous referees for their valuable comments which significantly improved the manuscript.

REFERENCES

[1.] Talu, S. Oil shale of Bahgecik (izmit). Report No. 4667, MTA, Ankara, 1967 (in Turkish).

[2.] Yanilmaz, E., ipeksever, M., Aslan, N. Report on Golpazan (Bilecik) oil shale field. Report No. 7060, MTA, Ankara, 1980 (in Turkish).

[3.] Taka, M., Sener, M. Oil shale facility of Himmetoglu (Goynuk-Bolu) field and their wells. Report No. 8533, MTA, Ankara, 1988 (in Turkish).

[4.] Sener, M., Senguler, I. Geology and economic usage of Beypazari oil shale. Report No. 9202, MTA, Ankara, 1991 (in Turkish).

[5.] Sener, M., Senguler, I. Geology, usage facility and firing test results in fluid bed of Seyitomer oil shale. Report. No. 9441, MTA, Ankara, 1992 (in Turkish).

[6.] Sener, M., Senguler, I. Geology and technologic usage facility of Hatildag (Bolu-Goynuk) oil shale. Report No. 9445, MTA, Ankara, 1992 (in Turkish).

[7.] Sener, M., Senguler, I., Kok, M. V. Geological considerations for the economic evaluation of oil shale deposits in Turkey. Fuel, 1994, 74(7), 999-1003.

[8.] Kara Gulbay, R. Rhenium and molybdenum in Tertiary oil shale deposits in Northwestern Anatolia, Turkey. Oil Shale, 2007, 24(3), 450-464.

[9.] Kara-Gulbay, R., Korkmaz, S. Element contents and organic matter-element relationship of the Tertiary oil shale deposits in northwest Anatolia, Turkey. Energ. Fuel, 2008, 22, 3164-3173.

[10.] Kara Gulbay, R., Korkmaz, S. Organic geochemistry, depositional environment and hydrocarbon potential of the Tertiary oil shale deposits in NW Anatolia, Turkey. Oil Shale, 2008, 25(4), 444-464.

[11.] Kok, M. V. Geological considerations for the economic evaluation of Turkish oil shale deposits and their combustion--pyrolysis behavior. Energ. Source. Part A, 2009, 32(4), 323-335.

[12.] Siyako, F., CoSar, N., Cokyaman, S., CoSar, Z. Tertiary geology and coal possibilities of Bozuyuk-Inonu-Eskisehir-Alpu-Beylikova-Sakarya areas. MTA Report No. 9281, Ankara, 1991 (in Turkish).

[13.] Gozler, Z., Cevher, F., Ergul, E., Asutay, J. H. Geology of the Central Sakarya and its southern area. MTA Report No. 9973, Ankara, 1996 (in Turkish).

[14.] Steffens, P. Sivrihisar Polatli (Eskisehir, Ankara) region lignite report. MTA Technical Report No. 6386, Ankara, 1970 (in Turkish).

[15.] Ocakoglu, F. A re-evaluation of the Eskisehir Fault Zone as a recent extensional structure in NW Turkey. J. Asian Earth Sc., 2007, 31(2), 91-103.

[16.] Senguler, I. Geology and coal potential of Eskisehir-Sivrihisar Basin (Turkey). Technical Report No. 11473, MTA, Ankara, 2011 (in Turkish).

[17.] Senguler, I., Akkiraz, M. S., Yanik, G. Palynology, Palaeoecology and Clay Mineralogy of Miocene Deposits in the Eskisehir Basin. Bulletin of Turkish Association of Petroleum Geologist (in press), Ankara, 2013.

[18.] Connan, J. Molecular geochemistry in oil exploration. In: Applied Petroleum Geochemistry (Bordenave, M. L., ed.). Editions Technip, Paris, 1993, 175-204.

[19.] Peters, K. E., Moldowan, J. M. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments. Prentice-Hall, Englewood Cliffs, N. J., 1993.

[20.] Hunt, J. M. Petroleum Geochemistry and Geology. W. H. Freeman and Company, New York, 1995.

[21.] Sinninghe Damste, J. S., Kenig, F., Koopmans, M. P., Koster, J., Schouten, S., Hayes, J. M., De Leeuw, J. W. Evidence for gammacerane as an indicator of water column stratification. Geochim. Cosmochimic. Ac., 1995, 59(9), 1895-1900

[22.] Peters, K. E., Walters, C. C., Moldowan, J. M. The Biomarker Guide. Biomarkers and Isotopes in Petroleum Exploration and Earth History, vol. 2, 2nd ed. Cambridge University Press, Cambridge, 2005.

[23.] Tissot, B. P., Welte, D. H. Petroleum Formation and Occurrence. Springer-Verlag, Heidelberg, 1984.

[24.] Moldowan, J. M., Seifert, W. K., Gallegos, E. J. Relationship between petroleum composition and depositional environment of petroleum source rocks. Am. Assoc. Petr. Geol. B., 1985, 69, 1255-1268.

[25.] Whitehead, E. V. The structure of petroleum pentacyclanes. In: Advances in Organic Geochemistry (Tissot, B., Biener, F., eds.), Editions Technip, Paris, 1974, 225-243.

[26.] Ekweozor, C. M., Okogun, J. I., Ekong, D. E. U., Maxwell, J. R. Preliminary organic geochemical studies of samples from the Niger delta (Nigeria): II. Analyses of shale for triterpenoid derivatives. Chem. Geol., 1979, 27(1-2), 29-37

[27.] Grantham, P. J., Posthuma, J., Baak, A. Triterpanes in a number of far-eastern crude oils. In: Advances in Organic Geochemistry (Bjoroy, M. et al., eds.). J. Wiley and Sons, New York, 1983, 675-683.

[28.] ten Haven, H. L., Rullkotter, J. The diagenetic fate of taraxer-14-ene and oleanene isomers. Geochim. Cosmochim. Ac., 1988, 52(10), 2543-2548.

[29.] Riva, A., Caccialanza, P. G., Quagliaroli, F. Recognition of 18b(H) oleanane in several crudes and Tertiary-Upper Cretaceous sediments. Definition of a New Maturity Parameter. In: Advances in Organic Geochemistry 1987 (Mattevelli, L., Novelli, L., eds.). Pergamon Press, Oxford, 1988, 671-675.

[30.] Udo, O. T., Ekweozor, C. M. Significance of oleanane occurrence in shales of Opuama Channel Complex, Niger Delta. Energ. Fuel., 1990, 4, 248-254.

[31.] Ourisson, G., Albrecht, P., Rohmer, M. Predictive microbial biochemistry from molecular fossils to prokaryotic membranes. Trends Biochem. Sci., 1982, 7(7), 236-239.

[32.] Volkman, J. K., Banks, M. R., Denwer, K., Aquino Neto, F. R. Biomarker composition and depositional setting of Tasmanite oil shale from northern Tasmania, Australia. In: 14th International Meeting on Organic Geochemistry, September 22, 1989, Abstract No 168, Paris.

[33.] Azevedo, D. A., Aquino Neto, F. R., Simoneit, B. R. T., Pinto, A. C. Novel series of tricyclic aromatic terpanes characterized in Tasmanian tasmanite. Org. Geochem., 1992, 18(1), 9-16.

[34.] Simoneit, B. R. T., Schoell, M., Dias, R. F., de Aquino Neto, F. R. Unusual carbon isotope compositions of biomarker hydrocarbons in a Permian tasmanite. Geochim. Cosmochim. Ac., 1993, 57(17), 4205-4211.

[35.] Riva, A., Riolo, J., Mycke, B., Ocampo, R., Callot, H. J., Albrecht, P., Nall, M. Molecular parameters in Italian carbonate oils: Reconstruction of past depositional environments. Abstract. In: 14th International Meeting on Organic Geochemistry, Paris, September 18-22, 1989, pp. 335.

[36.] Waples, D. W., Machihara, T. Biomarkers for Geologists: A Pratical Guide to the Application of Steranes and Triterpanes in Petroleum Geology. AAPG Methods in Exploration Series, No. 9, 1991.

[37.] Seifert, W. K., Moldowan, J. M. Use of biological markers in petroleum exploration. In: Methods in Geochemistry and Geophysics (Johns, R. B., ed.), 1986, 24, 261-190.

[38.] Seifert, W. K., Moldowan, J. M. The effect of thermal stress on source-rock quality as measured by hopane stereochemistry. In: Advances in Organic Ggeochemistry (Douglas, A. G., Maxwell, J. R., eds.). Pergamon Press, Oxford, 1980, 229-237.

[39.] Grantham, P. J. Sterane isomerisation and moretane/hopane ratios in crude oils derived from Tertiary source rocks. Org. Geochem., 1986, 9(6), 293-304.

[40.] Kvenvolden, K. A., Simoneit, B. R. T. Hydro thermally derived petroleum examples from Guaymas Basin, Gulf of California, and Escanaba Trough, northeast Pacific Ocean. Am. Assoc. Petr. Geol. B., 1990, 74, 223-237.

[41.] Hughes, W. B., Holba, A. G., Mueller, D. E., Richardson, J. S. Geochemistry of greater Ekofisk crude oils. In: Petroleum Geochemistry in Exploration of the Norvegian Shelf (Thomas, B. M., Dore, A. G., Eggen, S. S., Home, P. C., Larsen, R. M., eds.). Graham and Trotman, London, 1985, 75-92.

[42.] Sofer, Z., Zumberge, J. E., Lay, V. Stable carbon isotopes and biomarkers as tools in understanding genetic relationship, maturation, biodegradation, and migration of crude oils in Northern Peruvian Oriente (Maranon) Basin. Org. Geochem., 1986, 10(1-3), 377-389.

[43.] Cornford, C., Christie, O., Endresen, U., Jensen, P., Myhr, M.-B. Source rock and seep oil maturity in Dorset, southern England. Org. Geochem., 1988, 13(13), 399-409.

[44.] Kolaczkowska, E., Slougui, N. E., Watt, D. S., Marcura, R. E., Moldowan, J. M. Thermodynamic stability of various alkylated, dealkylated, and rearranged 17 aand 170-hopane isomers using molecular mechanics calculations. Org. Geochem., 1990, 16(4-6), 1033-1038.

[45.] Fowler, M. G., Brooks, P. W. Organic geochemistry as an aid in the interpretation of the history of oil migration into different reservoirs at the Hibernia K-18 and Ben Nevis I-45 wells, Jeanne d'Arc Basin, offshore eastern Canada. Org. Geochem., 1990, 16(1-3), 461-475.

[46.] Mukhopadhyay, P. K., Wade, J. A., Kruge, M. A. Organic facies and maturation of Jurassic/Cretaceous rocks, and possible oil-source rock correlation based on pyrolysis of asphaltenes, Scotian Basin, Canada. Org. Geochem., 1995, 22(1), 85-104.

[47.] Espitalie, J., Madec, M., Tissot, B., Mennig, J. J., Leplat, P. Source rock characterization methods of petroleum exploration. In: Proc. Offshore Technology Conference, 3(9), 1977, 439-444.

[48.] Dembicki Jr., H. Three common source rock evaluation errors made by geologists during prospect or play appraisals. Am. Assoc. Petr. Geol. B., 2009, 93(3), 341-356.

Presented by K. Kirsimae

Received October 2, 2013

Corresponding author: e-mail korkmaz@ktu.edu.tr

ILKER SENGULER (a), REYHAN KARA-GULBAY (b), SADETTIN KORKMAZ (b) *

(a) Energy Department, General Directorate of Mineral Research and Exploration, Ankara, Turkey

(b) Department of Geological Engineering, Karadeniz Technical University, Trabzon, Turkey

Table 1. Results of total organic carbon analyses (TOC) and
Rock-Eval pyrolysis for oil shale, coal bearing claystone and
coal samples from well 37 in the Eskisehir Basin

Sample    Depth, m   Lithology       TOC, %   [S.sub.1], mg
                                              HC/g rock

37-1      360        Oil Shale       9.34     0.97
37-2      361        Oil Shale       9.09     1.57
37-3      362        Oil Shale       10.49    1.15
37-4      363        Oil Shale       12.36    1.21
37-5      365        Oil Shale       6.39     0.56
37-6      367        Oil Shale       9.39     1.02
37-7      369        Oil Shale       11.43    1.39
37-8      371        Oil Shale       10.27    0.76
37-9      373        Oil Shale       11.77    1.55
37-10     375        Oil Shale       21.01    1.57
37-11     377        Oil Shale       37.15    2.78
37-12     383        Oil Shale       7.63     0.62
37-13     385        Coal            49.07    0.90
37-14     394        Coal bearing    34.17    1.52
                       claystone
Average                              17.11    1.26

Sample    [S.sub.2], mg   [S.sub.3], mg   [T.sub.max],
          HC/g rock       C[O.sub.2]/g    [degrees]C
                          rock

37-1      47.13           8.58            428
37-2      45.91           3.42            426
37-3      56.46           6.42            428
37-4      67.96           4.19            428
37-5      37.33           1.24            433
37-6      47.80           7.88            429
37-7      59.37           4..49           427
37-8      74.96           1.32            460
37-9      61.01           4.59            426
37-10     151.77          3.86            435
37-11     156.01          19.4            426
37-12     36.42           2.46            425
37-13     72.05           26.94           427
37-14     52.13           21.27           426

Average   69.02           8.29            430

Sample    HI, mg     OI, mg             PI, ([S.sub.1]/
          HC/g TOC   C[O.sub.2]/g TOC   [S.sub.1] +
                                        [S.sub.2])

37-1      505        92                 0.02
37-2      505        38                 0.03
37-3      538        61                 0.02
37-4      550        34                 0.02
37-5      584        19                 0.01
37-6      519        84                 0.02
37-7      519        39                 0.02
37-8      730        13                 0.01
37-9      518        39                 0.02
37-10     722        18                 0.01
37-11     420        52                 0.02
37-12     477        32                 0.02
37-13     147        55                 0.01
37-14     153        62                 0.03

Average   492        46                 0.02

Sample    [S.sub.2]/   PY, ([S.sub.1] +   RC, %
          [S.sub.3]    [S.sub.2])

37-1      5.49         48.1               5.01
37-2      13.42        47.48              4.93
37-3      8.79         57.61              5.42
37-4      16.22        69.17              6.34
37-5      30.10        37.89              3.16
37-6      6.07         48.82              4.95
37-7      13.22        60.76              6.13
37-8      56.79        75.72              3.86
37-9      13.29        62.56              6.31
37-10     39.32        153.34             7.97
37-11     8.04         158.79             22.81
37-12     14.80        37.04              4.35
37-13     2.67         72.95              41.20
37-14     2.45         53.65              28.40

Average   16.48        70.28              10.77

Sample    PC, %   Min C, %

37-1      4.33    0.77
37-2      4.16    0.99
37-3      507     0.63
37-4      6.02    0.73
37-5      3.23    0.20
37-6      4.44    0.90
37-7      5.3     0.23
37-8      6.41    0.23
37-9      5.46    0.21
37-10     13.04   1.38
37-11     14.34   8.64
37-12     3.28    1.54
37-13     7.87    5.58
37-14     5.77    1.09

Average   42.19   1.65

Table 2. Results of total organic carbon analyses (TOC) and
Rock-Eval pyrolysis for oil shale and coal samples from well
52 in the Eskisehir Basin

Sample    Depth, m   Lithology   TOC, %   [S.sub.1], mg
                                          HC/g rock

52-1      294        Oil Shale   8.29     0.67
52-2      295        Oil Shale   9.69     1.05
52-3      296        Oil Shale   11.7     0.76
52-4      298        Oil Shale   6.32     0.37
52-5      300        Oil Shale   10.16    1.05
52-6      303        Oil Shale   7.61     0.55
52-7      305        Oil Shale   11.06    1.13
52-8      307        Oil Shale   7.36     0.48
52-9      309        Oil Shale   11.03    1.50
52-10     311        Coal        47.18    1.05
52-11     312        Oil Shale   11.49    1.08
52-12     314        Oil Shale   8.27     2.37
52-13     316        Oil Shale   7.26     0.40
52-14     318        Oil Shale   20.22    1.00
52-15     323        Coal        51.76    0.57
Average                          15.29    0.94

Sample    [S.sub.2], mg   [S.sub.3], mg   [T.sub.max],
          HC/g rock       C[O.sub.2]/g    [degrees]C
                          rock

52-1      41.18           6.10            441
52-2      49.42           8.06            429
52-3      55.80           4.29            432
52-4      36.42           1.13            432
52-5      52.19           7.27            428
52-6      45.14           1.46            431
52-7      57.74           6.02            426
52-8      43.15           1.54            432
52-9      53.46           4.51            431
52-10     86.75           20.51           428
52-11     59.88           5.51            424
52-12     41.17           2.16            423
52-13     40.56           1.77            430
52-14     155.38          3.12            435
52-15     45.02           20.41           422
Average   57.55           6.26            429

Sample    HI, mg     OI, mg             PI, ([S.sub.1]/
          HC/g TOC   C[O.sub.2]/g TOC   [S.sub.1] +
                                        [S.sub.2])

52-1      497        74                 0.02
52-2      510        83                 0.02
52-3      477        37                 0.01
52-4      576        18                 0.01
52-5      514        72                 0.02
52-6      593        19                 0.01
52-7      522        54                 0.02
52-8      586        21                 0.01
52-9      485        41                 0.03
52-10     184        43                 0.01
52-11     521        48                 0.02
52-12     498        26                 0.05
52-13     559        24                 0.01
52-14     768        15                 0.01
52-15     87         39                 0.01
Average   492        41                 0.02

Sample    [S.sub.2]/   PY, ([S.sub.1] +   RC, %
          [S.sub.3]    [S.sub.2])

52-1      6.75         41.85              4.55
52-2      6.13         50.47              5.17
52-3      13.01        56.56              6.74
52-4      32.23        36.79              3.18
52-5      7.18         53.24              5.43
52-6      30.92        45.69              3.71
52-7      9.59         58.87              5.88
52-8      28.02        43.63              3.63
52-9      11.85        54.96              6.20
52-10     4.23         87.8               38.45
52-11     10.87        60.96              6.14
52-12     19.06        43.54              4.49
52-13     22.92        40.96              3.73
52-14     49.80        156.38             6.95
52-15     2.21         45.59              46.26
Average   16.98        58.49              10.03

Sample    PC, %   Min C, %

52-1      3.14    1.19
52-2      4.52    0.83
52-3      4.96    0.98
52-4      3.14    0.11
52-5      4.73    0.83
52-6      3.90    0.44
52-7      5.18    0.42
52-8      3.73    0.21
52-9      4.83    0.99
52-10     8.73    1.65
52-11     5.35    0.48
52-12     3.78    0.3
52-13     5.53    0.40
52-14     13.27   0.66
52-15     5.50    0.20
Average   5.35    0.65

Table 3. Results of total organic carbon analyses (TOC) and
Rock-Eval pyrolysis for oil shale, coal bearing claystone
and coal samples from well 53 in the Eskisehir Basin

Sample    Depth, m   Lithology      TOC, %   [S.sub.1], mg
                                             HC/g rock

53-1      355        Coal           48.95    1.06
53-2      366        Coal           50.44    0.81
53-3      382        Coal bearing   24.21    0.84
                       claystone
53-4      384        Oil Shale      8.82     0.71
53-5      386        Oil Shale      9.98     1.05
53-6      389        Oil Shale      9.20     0.73
53-7      393        Oil Shale      6.87     0.35
53-8      396        Oil Shale      11.04    1.06
53-9      398        Oil Shale      8.44     1.38
53-10     400        Oil Shale      20.37    1.07
53-11     402        Oil Shale      8.21     0.67
53-12     403        Oil Shale      6.92     0.90
53-13     405        Oil Shale      12.18    1.35
53-14     407        Oil Shale      7.94     0.71
53-15     409        Oil Shale      14.46    1.21
53-16     420        Coal           54.63    1.04
Average                             18.92    0.93

Sample    [S.sub.2], mg   [S.sub.3], mg   [T.sub.max],
          HC/g rock       C[O.sub.2]/g    [degrees]C
                          rock

53-1      28.81           18.55           396
53-2      48.49           25.00           423
53-3      22.88           13.69           416

53-4      40.09           5.53            421
53-5      51.00           8.52            424
53-6      36.11           4.65            424
53-7      37.84           1.53            430
53-8      58.82           5.97            426
53-9      41.20           2.16            427
53-10     158.25          3.06            437
53-11     49.89           1.39            431
53-12     34.60           1.57            425
53-13     63.11           4.50            424
53-14     44.72           1.40            428
53-15     81.31           3.76            424
53-16     60.12           22.57           421
Average   53.58           7.74            424

Sample    HI, mg     OI, mg             PI, ([S.sub.1]/
          HC/g TOC   C[O.sub.2]/g TOC   [S.sub.1] +
                                        [S.sub.2])

53-1      59         38                 0.04
53-2      96         50                 0.02
53-3      95         57                 0.04

53-4      455        63                 0.02
53-5      511        85                 0.02
53-6      392        51                 0.02
53-7      551        22                 0.01
53-8      533        54                 0.02
53-9      488        26                 0.03
53-10     777        15                 0.01
53-11     608        17                 0.01
53-12     500        23                 0.03
53-13     518        37                 0.02
53-14     563        18                 0.02
53-15     562        26                 0.01
53-16     110        41                 0.02
Average   426        39                 0.02

Sample    [S.sub.2]/   PY, ([S.sub.1] +   RC, %
          [S.sub.3]    [S.sub.2])

53-1      1.55         29.87              44.77
53-2      1.94         49.3               44.58
53-3      1.67         23.72              21.32

53-4      7.25         40.8               5.16
53-5      5.99         52.05              5.31
53-6      7.77         36.84              5.89
53-7      24.73        38.19              3.58
53-8      9.85         59.88              5.76
53-9      19.07        42.58              4.74
53-10     51.72        159.32             6.86
53-11     35.89        50.56              390
53-12     22.04        35.5               3.85
53-13     14.02        64.46              6.53
53-14     31.94        45.43              4.05
53-15     21.63        82.52              7.31
53-16     2.66         61.16              47.84
Average   16.23        54.51              37.97

Sample    PC, %    Min C, %

53-1      4.18     1.51
53-2      5.86     1.65
53-3      2.89     1.08

53-4      3.66     0.73
53-5      4.67     0.90
53-6      3.31     0.49
53-7      3.29     0.47
53-8      5.28     0.75
53-9      3.70     0.33
53-10     13.51    0.66
53-11     4.31     0.21
53-12     3.07     0.18
53-13     5.65     0.39
53-14     3.89     0.22
53-15     7.15     0.58
53-16     6.79     1.41
Average   5.08     0.72

Table 4. Parameters calculated from gas chromatograms
for oil shale from the Eskisehir Basin

Sample ID   Pr/Ph   Pr/n-C17   Ph/n-C18

37-9        0.67      1.30       0.47
52-12       0.17      0.35       0.38
53-9        0.96      0.97       2.20

Table 5. Biomarker composition based on m/z 217 mass chromatograms and
calculated parameters for oil shale samples from the Eskisehir Basin

Sample ID   [C.sub.27,28,29]   Iso-, normal and    20S/(20S + 20R)
               steranes           diasterane

37-9           36, 34, 30         35, 44, 21             0.40
52-12          27, 59, 14         22, 62, 16             0.31
53-9           36, 30, 34         14, 76, 10             0.05

Sample ID    [beta][beta]/    Diasterane/      Regular
            ([beta][beta] +    sterane      sterane/hopane
            [alpha][alpha])

37-9             0.46            0.42            0.17
52-12            0.39            0.37            0.08
53-9             0.18            0.14            0.20

Remark: 20S/(20S + 20R) sterane (for [C.sub.29]),
[beta][beta]/([beta][beta] + [alpha][alpha]) sterane (for [C.sub.29]),
diasterane/sterane (for [C.sub.27]), regular sterane/hopane =
[[C.sub.27,28,29] [alpha][alpha]/[beta][beta] (20S + 20R) steranes]/
[C.sub.29-33] hopanes.

Table 6. Biomarker composition based on m/z 191 mass
chromatograms and calculated parameters for oil shale
samples from the Eskisehir Basin

Sample ID   (1)    (2)    (3)    (4)    (5)

37-9        1.24   1.69   0.34   0.19   0.52
52-12       1.47   2.45   0.29   0.08   1.28
53-9        1.25   1.69   0.33   0.13   0.62

Sample ID   (6)    (7)    (8)    (9)    (10)

37-9        0.43   0.33   0.47   0.35   0.07
52-12       0.27   0.32   0.52   0.10   -53-9
0.46   0.34   0.54   0.19   0.14

(1)--[C.sub.29]/[C.sub.30] hopane; (2)--[C.sub.31] R homohopane/
[C.sub.30] hopane; (3)--22S/(22S + 22R) homohopane (for [C.sub.32]);
(4)--Ts/(Ts + Tm); (5)--moretane/hopane (for [C.sub.30]);
(6)--[C.sub.22]/[C.sub.21] tricyclic terpane; (7)--[C.sub.24]/
[C.sub.23] tricyclic terpane; (8)--([C.sub.19] + [C.sub.20])/
[C.sub.23] tricyclic terpane; (9)--[C.sub.23] tricyclic terpane/
([C.sub.23] tricyclic terpane + [C.sub.30]hopane);
(10)--[C.sub.29]Ts/([C.sub.29]Ts + [C.sub.29]H).
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