Jurf ed Darawish

A large variation in the distribution patterns of C20 isoprenoid thiophenes has been encountered upon analysis of sediments and oils ranging from normal marine saline to hypersaline (16). Figure 8 shows that in samples representing a normal marine salinity environment (Monterey Shale-Naples and -El Capitan Beach, Jurf ed Darawish-45) isoprenoid thiophenes VI and VII are dominant whereas in samples from hypersaline palaeoenvironments (Sicily seep oil-E2, Rozel Point oil) isoprenoid thiophene V and the so-called midchain isoprenoid thiophenes (I-IV) are relatively abundant. C20 isoprenoid bithiophenes (VIII-X) only occur when the midchain isoprenoid thiophenes are relatively abundant (Figure 9). 

In many samples reflecting hypersaline palaeoenvironments a series of extended hopanes and/or hop-17(21)-enes dominated by C35 members have been observed (7,8,31,33). It should be noted, however, that similar distribution patterns are also encountered in samples originating from normal marine salinity sediments such as those from the Brazilian marginal basins (31), the Serpiano shale (44), the Phosphoria Retort shale (45) and the Jurf ed Darawish Oil Shale (23, 46). 

Desulfurisation of polar fractions of relative immature oils and sediment from hypersaline palaeoenvironments yields n-alkanes with strong even-over-odd carbon number predominances (20,42 e.g., Figure 11). This phenomenon is, however, not restricted to samples from hypersaline palaeoenvironments (e.g., Jurf ed Darawish Oil Shale, Monterey Shale). 

The upper Cretaceous Jurf ed Darawish oil shale (thickness ca. 120m 45m-165m depth) in the Ghareb Formation is a calcareous, bituminous marl (commercially termed oil shale), which is located 130 km south of Amman, Jordan (14). The organic matter in this sequence is thermally immature ("vitrinite" reflectance = 0.28-0.31 % L. Buxton, pers. comm.)... 

Table I. Samples studied and some geochemical bulk data of the Jurf ed Darawish oil shale...

Figure 1. Lithology, variations with depth of (a) carbonate content, (b) A1203 content, (c) P205 content, (d) total S content (organically and inorganically bound sulfur) and (e) total organic carbon for the Jurf ed Darawish oil shale and the three lithologically defined Facies (bituminous limestone, bituminous calcareous marl and phophorite) are schematicaly depicted.

Jurf ed Darawish-59 bitumen saturated HC fraction Facies A... 

Jurf ed Darawish-137 bitumen saturated HC fraction Facies B... 

Figure 5. Gas chromatograms (HT-5) of the A2 fractions of the indicated samples from Facies A, B and C of the Jurf ed Darawish oil shale. The peak assignments are listed in Table III.

Figure 6. Depth profiles of (a) total extractable alkylthiophenes and (b) thiophenes with linear carbon skeletons, (c) thiophenes with isoprenoid carbon skeletons, (d) thiophenes with highly branched isoprenoid carbon skeletons and (e) thiophenes with mid-chain dimethylalkane carbon skeletons relative to the total alkylthiophenes for the Jurf ed Darawish oil shale.

Figure 9. (a) Depth profiles of C37 and C38 mid-chain 2,5-dialkylthiophenes XI for the Jurf ed Darawish oil shale, (b) Formation of C37 and C38 mid-chain 2,5-dialkylthiophens XI by sulfur (H2S) incorporation into triunsaturated C37 and C38 methylketones IX or hydrocarbons X. 

Figure 13. Carbon number distribution patterns of major isoprenoid thiophenes for the Jurf ed Darawish oil shale samples indicated.

Separation methods. Extraction and fractionation (Figure 1) methods have been described elsewhere (16). The kerogen from Jurf ed Darawish-156 was concentrated by decarbonating the extracted whole rock followed by reextraction. The kerogen from the Monterey-25 was fully isolated using standard HC1/HF techniques. Asphaltene fractions were obtained and purified from bitumens by repeated precipitations with n-heptane. 

Figure 2a shows the total ion chromatogram (TIC) of the flash pyrolysate of a sulfur-rich (Type II-S) kerogen from the Jurf ed Darawish Oil Shale. The major peaks are alkylated thiophenes, shown more clearly in... 

Figure 2. Total ion currents (TIC) of flash pyrolysates of several high-molecular-weight fractions of the Jurf ed Darawish-156.

Table I. Major alkylthiophenes identified in pyrolysates of the Jurf ed Darawish Oil Shale and Monterey kerogens and asphaltenesa...

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