Characterization of paraffinic deposits in crude oil storage tanks using high temperature gas chromatography

Problems related to the crystallization and deposition of heavy organic fractions during production, transportation and storage of crude oils can lead to considerable financial losses for the petroleum industry. The heavy organic fractions may include paraffins or waxes, resins, asphaltenes, and organometallic compounds that exist in crude oils in various quantities, states, and forms. The severity of the deposition problems varies widely and depends on factors such as the crude oil composition, operating conditions in the reservoir and production procedures. Problems associated with the solid deposits may be encountered anywhere in the production process from the reservoir to the refinery. In this paper, it is proposed to focus on production problems associated with certain fields in Tunisia. The problems manifested themselves through the accumulation of solid deposits in the storage tanks at a Tunisian terminal and originated from the mixtures of various crude oils transported to the terminal by pipeline. The principal analytical method for the characterization of the solids was high temperature gas chromatography following concentration of the wax fraction through a modification of the conventional acetone precipitation technique.     

Evaluating the timing of oil expulsion: about the inverse behaviour of light hydrocarbons and oil asphaltene kinetics

This paper deals with natural temperature records in the heavy (asphaltenes) and the light fractions (C₇—light hydrocarbons) of petroleum. Two sets of marine oils formed from different source rocks and petroleum systems were studied using asphaltene kinetics and light hydrocarbon analysis. Both fractions have been reported to contain information about the temperature the respective oils have been exposed to in the subsurface. These indicated temperatures generally correspond to the conditions in the source rock when expulsion occurred. Bulk kinetic analysis of reservoir oil asphaltenes as well as light hydrocarbon (LH) analysis (of dimethylpentanes) were used here in order to evaluate the expulsion temperatures. Surprisingly, when considering information coming from both fractions, an inverse trend between LHs expulsion temperatures (Ctemp) and asphaltenes (Tasph.) can be observed—high T_asph (asphaltene temperatures) occur with low LH C_temp (light hydrocarbon expulsion temperatures) and low T_asph can be observed when Ctemp is high. These differences are of fundamental importance for the use of such geochemical data in calibrating numerical basin models. The reason for this inverse behaviour is possibly due to the different expulsion behaviour of light hydrocarbons and the heavy fraction of oils, especially when the source rocks contain only moderate amounts of organic matter. In addition it has to be considered that the temperature predictions obtained using asphaltene kinetic analysis are related to the onset temperature of petroleum expulsion, while light hydrocarbons provide, at best, average expulsion temperatures.     

Terrigenous plant wax inputs to the Arabian Sea: Implications for the reconstruction of winds associated with the Indian Monsoon

We have determined the accumulation rates and carbon isotopic compositions (δ¹³C) of long-chain (C₂₄-C₃₂) terrigenous plant wax fatty acids in 19 surface sediment samples geographically distributed throughout the Arabian Sea in order to assess the relationship between plant wax inputs and the surrounding monsoon wind systems. Both the accumulation rate data and the δ¹³C data show that there are three primary eolian sources of plant waxes to the Arabian Sea: Africa, Asia, and the Arabian Peninsula. These sources correspond to the three major wind systems in this region: the summer (Southwest) monsoon, the winter (Northeast) monsoon, and the summer northwesterlies that blow over the Arabian Peninsula. In addition, plant waxes are fluvially supplied to the Gulf of Oman and the Eastern African margin by nearby rivers. Plant wax δ¹³C values reflect the vegetation types of the continental source regions. Greater than 75% of the waxes from Africa and Asia are derived from C₄ plants. Waxes delivered by northwesterly winds reflect a greater influence (25-40%) of C₃ vegetation, likely derived from the Mesopotamian region. These data agree well with previously published studies of eolian dust deposition, particularly of dolomite derived from the Arabian Peninsula and the Mesopotamian region, in surface sediments of the Arabian Sea. The west-to-east gradient of plant wax δ¹³C and dolomite accumulation rates are separately useful indicators of the relationship between the northwesterly winds and the winds of the Southwest monsoon. Combined, however, these two proxies could provide a powerful tool for the reconstruction of both southwest monsoon strength as well as Mesopotamian aridity.     

Characterization of high molecular weight biomarkers in crude oils

High-temperature gas chromatography (HTGC) has enhanced our ability to characterize hydrocarbons extending to C₁₂₀ in crude oils. As a result, hydrocarbons in waxes (> C₂₀) have been observed to vary significantly between crude oils, even those presumed to originate from the same source. Prior to this development, microcrystalline waxes containing hydrocarbons above C₄₀ were not characterized on a molecular level due to the analytical limitations of conventional gas chromatography. Routine screenings of high pour-point crude oils by high-temperature gas chromatography has revealed that high molecular weight hydrocarbons (> C₄₀) are very common in most oils and may represent 2% of the crude oil. Precise structures, origins, and significance of these high molecular weight compounds remain elusive. As a preliminary step to expand our knowledge of these compounds their general molecular structures and formulas have been investigated in this study. Initial results suggest that the major high molecular weight compounds include a homologous series of n-alkanes, methylbranched alkanes, alkylcyclopentanes, alkylcyclohexanes, alkylbenzenes and alkylcycloalkanes.     

The influence of marine and terrestrial source material on the composition of petroleum

This paper consists of two interrelated parts. In the first part, the influence of the composition of sediment organic matter on crude oil composition is discussed. The second part deals with the origin of normal paraffins in petroleum.Source beds with abundant terrestrial plant matter generate heavy hydrocarbons rich in five-ring naphthenes. Unless such source beds are exposed to a high temperature for a prolonged time, the oils released are also rich in five-ring naphthenes. Such oils are rare; thus far the only examples found are some Eocene Wilcox oils from the Texas Gulf Coast and some Eocene Green River oils from the Uinta Basin, Utah. Normally, oil source beds are not rich in terrestrial plant matter and the five-ring naphthene content of the source bed hydrocarbons, as well as that of the produced oils, is low.The n-paraffins generated by oil source beds rich in terrestrial plant matter are characterized by abnormally low (C₂₁ + C₂₂)/(C₂₈ + C₂₉) ratios of 0.6–1.2. In oils of dominantly marine origin, this ratio is in the range 1.5–5.0. The ratio of marine to terrestrial organic matter in source beds appears to influence both the naphthene composition and the n-paraffin composition of the generated oils.Evidence is presented that petroleum n-parainns originate from slow thermal cracking of fatty acids contained in fats and waxes. Reaction equations are discussed which explain the major geochemical observations, including the difference in carbon-number distribution of the assumed parental fatty acids and of their descendant n-paraffins. In normal oils, which originate mostly from fat rich marine organic matter, the n-paraffin concentration tapers off above C₂₀. The molecular weight range of the fatty acids of plant waxes is considerably higher than that of fats. If plant waxes contribute strongly to the oil source material, the molecular weight distribution of the petroleum n-paraffins formed is abnormal and high carbon numbers in the C₂₄-C₃₂ range dominate.     

Thermal alteration experiments on organic matter from recent marine sediments in relation to petroleum genesis

Three fractions of organic matter: lipid (benzene:methanol-extractable), humic acid (alkali-extractable) and kerogen (residue) were extracted from a young marine sediment (Tanner Basin, offshore southern California) and heated for different times (5–116 hr) and temperatures (150°–410°C). The volatile (gases) and liquid products, as well as residual material, were then analyzed. On a weight basis, the lipid fraction produced 58% of the total identified n-alkanes, the kerogen fraction 41%, and the humic acid <1%. Whereas n-alkanes produced from lipid show a CPI > 1.0, those produced by thermal alteration of kerogen display a CPI < 1.0. The volatiles produced by heating the lipid and humic acid fractions were largely CO₂ and water, whereas those produced from heated kerogen also included methane, hydrogen gas and small amounts of C₂–C₄ hydrocarbons. A mechanism for hydrocarbon production due to the thermal alteration of organic constituents of marine sediment is discussed.     

The effect of material properties on growth rates of folding and boudinage: Experiments with wax models

The growth of unstable structures was studied experimentally in layered wax models. The rheological properties of the two wax types were determined independently by a series of cylinder compression tests. Both waxes enhibited (1) a non-Newtonian stress vs strain-rate relationship (2) strain softening and (3) temperature-dependent viscosity. The stress-strain-rate relationships approximated a power-law, with stress exponents of 5 for the microcrystalline wax and 1.8 for paraffin wax.Blocks of paraffin with a single embedded layer of microcrystalline wax were deformed in two-dimensional pure shear with the layer oriented either parallel to the compressive strain axis so that it shortened and folded, or perpendicular to that axis so that it would stretch and boundinage would form. The growth rates of tiny initial disturbances were measured. The growth rates for folding and boudinage were much higher than could be accounted for by theories assuming Newtonian material properties. Theories taking non-Newtonian behaviour into account (Smith, R. B. 1975. Bull. geol. Soc. Am.86, 1601–1609; Fletcher, R. C. 1974. Am. J. Sci.274, 1029–1043) better describe the folding growth rates. Boudinage, however, grew almost three times faster than would be predicted even by existing non-Newtonian theory. A possible reason for this discrepancy is that the waxes do not exhibit steady-state creep as assumed in the theory. We, therefore, extend the theory to include strain-softening. The crucial step in this theory is the use of a scalar measure of the deformation as a state variable in the constitutive law. In this way the isotropic manifestation of strain-softening can be taken into account. The analysis shows that strain-softening can lead to greatly increased boudinage growth rates while having little influence on the growth rates of folds, which is in agreement with the experiments.     

The use of carbon and sulfur isotopes as correlation parameters for the source identification of beach tar in the southern California borderland

Carbon and sulfur isotope ratios and total sulfur content are used to correlate beach tars depositing near Los Angeles with their probable sources. Analysis is confined strictly to the asphaltene fraction of petroleum owing to the insensitivity of this fraction to weathering processes.The δ¹³C, δ³⁴S and % S of the asphaltene fraction of natural offshore seep oils range from ?22.51 to ?23.20%., +7.75 to + 15.01%. and 4.45 to 8.27%, respectively. Values for local offshore production wells overlapped those for the natural seepage, ranging from ?22.10 to ?22.85%., ?2.96 to 13.90%., and 0.81 to 8.00%. Analytical values for these parameters show that tanker crudes imported into the area are not similar to the California oils. Analysis of the same parameters in beach tars collected during 1976–1977 indicates a close match with the potential source oils, thus it is concluded that these parameters are useful for identifying petroleum sources, even after 2–4 weeks of weathering. Results indicate that 55% of the tars in Santa Monica Bay are derived from natural oil seepage 150km to the northwest at Coal Oil Point, 26% are derived from natural oil seepage in Santa Monica Bay, and 19% are derived from unknown sources.Models of tar transport are inferred which are consistent with the seasonal deposition pattern. Tar from Coal Oil Point natural oil seeps is transported southward in the southern California gyre during the spring, summer and fall seasons, but probably undergoes northward transport during the winter season due to the surfacing of the Davidson Current. Tar from the Santa Monica Bay natural oil seeps moves onshore, but deposition rate seems to depend on seepage flow rate.     

石油沥青质的吸附、沉淀机理及其影响因素

对于原油中石油沥青质的存在状态尚无统一认识,存在多种石油胶体体系理论模型。沥青质有两种方式从石油中分离出来,即吸附和沉淀,它们具有完全不同的机理。吸附的沥青质不能被溶解,要通过解吸才能消除,且解吸过程相对溶解而言很慢。沉淀是由于石油胶体体系的变化引起的,而吸附则是由石油胶体体系以及体系外的水介质环境和周围岩石矿物特征等所控制的。影响吸附的主要因素有:矿物本身的化学性质和结构特征、矿物质表面水层的性质、原油组成。影响沉淀的因素主要有:原油的组成、温度和压力、石油所处的状态、孔隙特征。低渗储层比高渗储层更容易导致沥青质的沉淀。     

Biomarker lipids of the freshwater fern Azolla and its fossil counterpart from the Eocene Arctic Ocean

Eocene sediments recovered from the Lomonosov Ridge in the central Arctic Ocean during Integrated Ocean Drilling Program Expedition 302 contain high amounts of fossil remains of the free floating freshwater fern Azolla. Both extant Azolla and the sediments from the Arctic Azolla interval were found to contain relatively high quantities of compounds identified as 1,ω20 C₃₀–C₃₆ diols. Furthermore, structurally related mid-chain hydroxy fatty acids, long chain n-alkanols and keto-ols were discovered. The different series have a common feature: there is always a hydroxy group at the ω20 position. In addition, structurally related C₂₉ ω20,ω21 diols, C₂₉ 1,20,21 triols, C₂₉ dihydroxy fatty acids as well as a series of wax esters containing these mono- and dihydroxy lipids are reported. Selective extraction of Azolla surface lipids revealed that these compounds are most likely present in the leaf waxes of the fern. The suite of long-chain, mid-chain ω20 hydroxy wax constituents is described for the first time. As they are well preserved in the Eocene sediments, these lipids may serve as palaeo-environmental indicators of the Arctic Azolla interval and as markers for the past occurrence of Azolla in general.     

Re-Os elemental and isotopic systematics in crude oils

Analysis of 12 worldwide oil samples show that Re and Os abundances are positively correlated with the asphaltene content of oil. Light oils with <1% asphaltene content have basically no measurable Re or Os. Within oil, Re and Os are present dominantly in the asphaltene fraction (>83%), with <14% Re and Os found in the maltene fraction, this distribution is similar to other trace metals such as V and Mo. Rhenium and Os could be present in oil as metalloporphyrin complexes, but given their abundance in the asphaltene component they are also likely bound by heteroatomic ligands. The ¹⁸⁷Re/¹⁸⁸Os and ¹⁸⁷Os/¹⁸⁸Os values in asphaltene calculated at the estimated time of oil generation (Os_i) are similar to those of the whole oil, as expected from the elemental results. This suggests that the asphaltene fraction can be used to approximate the Re-Os isotopic compositions of the whole oil. Os isotopic compositions in oils show a considerable range, from ¹⁸⁷Os/¹⁸⁸Os of 1.9-6.0, and they correlate positively with the age of the proposed source rock. Re/Os ratios also show a large range and overlap the Re/Os ratios found in typical oil source rocks such as organic rich shale.     

Hydrocarbon source potential and depositional environment of the Surma Group shales of Bengal basin,Bangladesh

Surma Group is the most important geological unit of Bengal basin, Bangladesh, because petroleum resources occur within this group. It is mainly composed of alternation of shale and sandstone and the shale fraction has long been considered as source rocks and the sandstone fraction as reservoir. These source and reservoir rocks have been studied by different authors by different approach but none of them adopted organic geochemistry and organic petrology as a means of study of source rock and their possible depositional environment. A total of thirty shale core samples have been collected from eight different gas fields to fulfill the short coming. The collected samples have been subjected to Source Rock Analysis (SRA) and/or Rock-Eval (RE) followed by pyrolysis gas chromatography (PyGC), gas chromatography mass spectrometry (GCMS), elemental analysis (EA) and organic petrological study such as vitrinite reflectance measurement and maceral analysis. The analyzed organic matter extracted from the shales of Surma Group consists mainly of Type III along with some Type II kerogen. The studied shales are mostly organically lean (TOC ±1%) and the extracted organic matter is fair to moderate. Based on these results, the analyzed shales have been ranked as poor (mostly) to fair quality source rock. The organic matter of the analyzed shale samples is thermally immature to early mature for hydrocarbon generation considering their T_max and measured mean vitrinite reflectance values. The hopane 22S/(22S + 22R), moretane/hopane ratio and sterane parameters are also in good agreement with these thermal maturity assessments. The predominance of odd carbons over even carbons (most common) and/or even carbons over odd carbon numbered n-alkanes, moderate Pr/Ph ratio, low to high Tm/Ts ratio, comparative abundance of sterane C₂₉ (i.e., C₂₉ >C₂₇>C₂₈), Pr/nC₁₇ — Ph/nC₁₈ values, C/S ratio and dominance of vitrinite macerals group with the presence of liptinite macerals demonstrate that the organic matter has derived mainly from terrestrial inputs with an insignificant contribution from the marine sources. The condition of deposition alternates from oxic to anoxic.     

Thermal treatment of the Athabasca oil sand bitumen and its component parts

The Athabasca oil sand bitumen, and its major component fractions, have been heated with and without added montmorillonite to simulate natural geological diagenesis. The products of the treatment of the whole bitumen were found to be essentially the sum of the products of the treatment of the component parts. The saturated hydrocarbon fraction underwent little change, with only minor cracking apparent. Some cracking and polymerization of the aromatic hydrocarbon fraction was noted. Geochemical analysis of these products indicated that the simulation had caused a continuation of the normal petroleum maturation sequence towards coke and gas. Treatment of the polar fraction and asphaltenes caused a continuation of the maturation sequence towards a ‘crude oil’, further treatment of which continued towards coke and gas. Geochemical examination of this ‘crude oil’ yielded information on the past history of the bitumen from the time of asphaltene formation. The geochemical evidence indicates that the Athabasca bitumen may have originated in an unusual marine environment, and that the maturation and exodus from its source rock differed from that of conventional crude oils. The overall results indicate that, except for the maturation of the polar and asphaltene fractions, the bio-degradation of a crude oil is not reversible by diagenetic means.     

Solubility of crude oil in methane as a function of pressure and temperature

The solubility of a 44° API (0.806 sp. gr.) whole crude oil has been measured in methane with water present at temperatures of 50 to 250°C and pressures of 740 to 14,852 psi, as have the solubilities of two high molecular weight petroleum distillation fractions at temperatures of 50 to 250°C and pressures of 4482 to 25,266 psi. Both increases in pressure and temperature increase the solubility of crude oil and petroleum distillation fractions in methane, the effect of pressure being greater than that of temperature. Unexpectedly high solubility levels (0.5–1.5 grams of oil per liter of methane—at laboratory temperature and pressure) were measured at moderate conditions (50–200°C and 5076–14504 psi). Similar results were found for the petroleum distillation fractions, one of which was the highest molecular weight material of petroleum (material boiling above 266°C at 6 microns pressure). Unexpectedly mild conditions (100°C and 15,200 psi; 200°C and 7513 psi) resulted in cosolubility of crude oil and methane. Under these conditions, samples of the gas-rich phase gave solubility values of 4 to 5 g/l, or greater.Qualitative analyses of the crude-oil solute samples showed that at low pressure and temperature equilibration conditions, the solute condensate would be enriched in C₅–C₁₅ range hydrocarbons and in saturated hydrocarbons in the C₁₅₊ fraction. With increases in temperature and especially pressure, these tendencies were reversed, and the solute condensate became identical to the starting crude oil.The data of this study, compared to that of previous studies, shows that methane, with water present, has a much greater carrying capacity for crude oil than in dry systems. The presence of water also drastically lowers the temperature and pressure conditions required for cosolubility.The data of this and/or previous studies demonstrate that the addition of carbon dioxide, ethane, propane, or butane to methane also has a strong positive effect on crude oil solubility, as does the presence of fine grained rocks.The n-paraffin distributions (as well as the overall composition) of the solute condensates are controlled by the temperature and pressure of solution and exsolution, as well as by the composition of the original starting material. It appears quite possible that primary migration by gaseous solution could ‘strip’ a source rock of crude-oil like components leaving behind a bitumen totally unlike the migrated crude oil. The data of this study demonstrate previous criticisms of primary petroleum migration by gas solution are invalid; that primary migration by gaseous solution cannot occur because methane cannot dissolve sufficient volumes of crude oil or cannot dissolve the highest molecular weight components of petroleum (tars and asphaltenes).     

Characterization of nC7-soluble fractions of the products from mild oxidation of asphaltenes

A significant quantity of hydrocarbons (including alkanes) is occluded in the skeleton of the asphaltene molecule. The hydrocarbons are probably remnants of the “original oil” which had been retained within the asphaltene matrix and protected from the secondary alteration processes that occurred subsequently in the oil reservoirs. In this work we report that oxidation of asphaltenes by stirring with 30%H₂O₂–HAc or NaIO₄–NaH₂PO₄ can release nC₇-soluble oxidized products, including the occluded hydrocarbons. Characterization of the nC₇-soluble fractions of oxidized products can be applied to highlight some geochemical problems, such as in studies of oil–oil correlation, oil–source correlation and secondary alterations of oil reservoirs. It will be especially useful to recover the original geochemical information of some oil reservoirs heavily degraded by post-depositional processes.     

Distribution patterns and stable carbon isotopic composition of alkanes and alkan-1-ols from plant waxes of African rain forest and savanna C3 species

Leaf wax components of terrestrial plants are an important source of biomass in the geological records of soils, lakes and marine sediments. Relevant to the emerging use of plant wax derived biomarkers as proxies for past vegetation composition this study provides key data for C₃ plants of tropical and subtropical Africa. We present analytical results for 45 savanna species and 24 rain forest plants sampled in their natural habitats. Contents and distribution patterns of long chain n-alkanes (n-C₂₅ to n-C₃₅) and n-alkan-1-ols (n-C₂₄ to n-C₃₄) as well as bulk and molecular carbon isotopic data are presented. The variations of the analysed parameters among different growth forms (herb, shrub, liana and tree) are small within the vegetation zones, whereas characteristic differences occur between the signatures of rain forest and savanna plants. Therefore, we provide averaged histogram representations for rain forest and savanna C₃ plants.The findings were compared to previously published data of typical C₄ grass waxes of tropical and subtropical Africa. Generally, trends to longer n-alkane chains and less negative carbon isotopic values are evident from rain forest over C₃ savanna to C₄ vegetation. For n-alkanols of rain forest plants the maximum of the averaged distribution pattern is between those of C₃ savanna plants and C₄ grasses. The averaged presentations for tropical and subtropical vegetation and their characteristics may constitute useful biomarker proxies for studies analysing the expansion and contraction of African vegetation zones.     

Source rock-crude oil correlation by isotopic type-curves

An isotopic type-curve has been defined based on the ${}^{13}\text{C}{}^{12}\text{C}$ ratios of the saturated, aromatic, heterocomponent (NOSs), and asphaltene fractions of crude oils. These fractions show ¹³C enrichments with increasing polarity or polarizability. This systematic pattern can be used to estimate the ${}^{13}\text{C}{}^{12}\text{C}$ ratio of the kerogen from which the oil had been generated. Genetically associated source rock oil pairs have been used to show that the difference between the measured and the estimated δ-values of kerogen is about ?0.5%., and between the δ-values of the kerogen and the asphaltene fraction is approximately +0.6%.     

Biomarker distributions in asphaltenes and kerogens analysed by flash pyrolysis-gas chromatography-mass spectrometry

Biomarker distributions in a suite of asphaltenes and kerogens have been analysed by flash pyrolysis directly coupled to a GCMS system. Attention has been focussed on biomarkers of the sterane and triterpane types. The sample suite under investigation consists of sediments with different kerogen types and some crude oils. Biomarker distributions in the pyrolysates have been compared with the “free” biomarkers in the corresponding saturated hydrocarbon fractions.The analyses show significant differences between the distributions of the free biomarkers and those in the pyrolysates. The latter have lower amounts of steranes while diasteranes are absent or present at low concentrations only. In the triterpane traces a shift of maximum intensity from C₃₀ (free compounds) to C₂₇/C₂₉ is observed. Furthermore, the pyrolysates contain a set of triterpenes (not present among the free compounds), and there is a selective loss of “non-regular” triterpanes that are present in the saturated hydrocarbon fractions. The observed differences between pyrolysates and free hydrocarbons can be explained partly by the processes occurring during pyrolysis such as bond rupture and subsequent stabilisation of primary pyrolysis products. To a certain extent these differences also show that maturation processes occurring in sediments have effects on free biomarker molecules different from those on molecules that are enclosed in a macromolecular matrix (kerogen or asphaltenes).Differences between biomarker distributions of asphaltene and kerogen pyrolysates are relatively small. A comparison with the pyrolysates from extracted whole sediments suggests that these differences are mainly caused by interactions between the organic material and the mineral matrix during pyrolysis.Oil asphaltenes behave differently from sediment asphaltenes as their pyrolysates are more similar to the corresponding saturated hydrocarbon fractions, i.e. the differences described above are observed to a much smaller extent. This different behaviour appears to be the result of coprecipitation of a part of the maltene fraction with the oil asphaltenes.     

Biodegradation of petroleum by <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> isolated from drilling fluid

The removal of petroleum and petroleum-based products from the environment is of great importance. The objectives of this study were to investigate the most suitable physiological conditions and the effects of additional carbon, nitrogen and surfactant sources on petroleum biodegradation by Klebsiella pneumoniae ATCC13883 isolated from drilling fluid and to evaluate petroleum biodegradation with detailed hydrocarbon analysis by GC–MS. The results indicated that the highest biodegradation rate of 66.5% for K. pneumoniae was obtained under the conditions of pH 7, petroleum concentration 1% (v/v) and 7-day incubation at 150 rpm and 25 °C, proving to be the most effective physical conditions for petroleum biodegradation in this present study. Additional sources such as Triton X: 100, glucose and yeast extract significantly enhanced the petroleum biodegradation of K. pneumoniae to 68, 71 and 72.5%, respectively. In the last stage of this study, biodegradation rates were above 90% for hydrocarbons ranging from C₁₀ and C₂₀, above 70% for hydrocarbons ranging from C₂₁ and C₂₂ and above 40% for hydrocarbons ranging from C₃₁ and C₃₂. In conclusion, oil field adapted K. pneumoniae could efficiently degrade short-, medium- and long-chain alkanes in petroleum and thus is a potential source for advanced petroleum treatment.     

Higher plant vegetation changes during Pliocene sapropel formation

The δ¹³C values of higher plant wax C_27–33 n-alkanes were determined in three, time-equivalent Pliocene (2.943 Ma) sapropels and homogeneous calcareous ooze from three different sites forming an east-west transect in the eastern Mediterranean Basin in order to study the composition of the vegetation on the continents surrounding the Mediterranean Sea. A two-end member mixing model transformed the measured δ¹³C values into the contribution of C₄ plants to the terrestrial vegetation. These calculations indicated a high C₄ plant contribution (i.e. 40–50%) in the periods just before and just after sapropel formation. During sapropel deposition the C₄ plant contribution increased by up to 20% at all sites. This is interpreted to record the increased overall plant coverage of the Mediterranean borderlands resulting from the change in formerly barren desert areas into C₄ grass-dominated savannahs as a response to the wetter climate during sapropel deposition. Enhanced accumulation rates (ARs) of long-chain n-alkanes (C_27–33) and n-alkan-1-ols (C_26–30) towards the middle of the sapropel in concert with a decrease in the Ti/Al ratio confirm an increased delivery of terrigenous organic matter at all sites. These biomarkers were probably predominantly fluvially transported to the Mediterranean Sea, not only by the Nile but by fossil wadi river systems on the northern African continent.