Kerogen composition

Relationship between kerogens and asphaltenes have taken on new meaning in the last few years especially for relatively low maturity oils. Asphaltene composition can give inferences about the source kerogen composition when kerogen data are unavailable (53.58-59). Asphaltenes are defined as materials soluble or peptized in oil or bitumen that precipitate when... 

Artificial Maturation. Laboratory maturation studies provide a means to determine the influence of temperature on kerogen composition, since other variables (e.g. source input) can be eliminated. In order to study the behaviour of organically bound sulfur under these controlled conditions, Py-GC-FID/FPD was performed on a suite of solvent-extracted residues from sealed vessel (hydrous pyrolysis) experiments aimed at simulating maturation over the range involved in petroleum generation. 

The purpose of this paper is to report the preliminary results of a study of Upper Devonian shales by NMR in an attempt to understand regional variations in kerogen composition as related to the evolution of oil and gas. 

Fig. 4.15 A van Krevelen plot showing the evolutionary trends of the main kerogen types (shaded bands after Behar Vandenbroucke 1987) and most coals (between solid lines after Killops etal. 1998). With increasing maturity kerogens follow a path towards the origin, as shown for the low/high-H coals boundary.The main hydrocarbon-generation zones are shown, with their approximate rank boundaries (as vitrinite reflectance values, %Ro), together with the effect of loss of various volatiles from different kerogen compositions (CH2 = oil). Points represent the composition of kerogens in Fig.4.14.

Fig. 4. 29 Trends in petroleum generation (gen) and expulsion (exp) for source rocks of varying kerogen composition (at a mean heating rate of 5°C MyE1 after Mackenzie Quigley 1988). Concentrations refer to kg of kerogen per tonne of rock.

Tissot, B.P., and D.H. Welte Kerogen, composition and classification. In Petroleum formation and occurrence, ed. by B.P. Tissot and D.H. Welte. Berlin Heidelberg New York Springer. 1978. 

Their chemical compositions are very complex and depend essentially on their age, that is, the phase of development of the kerogene, regardless of the origin of the crude (Speight, 1991) (see Chapter 1). 

Oil shale deposits were formed in ancient lakes and seas by the slow deposition of organic and inorganic remains. The geology and composition of the inorganic minerals and organic kerogen components of oil shale vary with deposit locations throughout the world (1) (see also Fuel RESOURCES Petroleum). 

Geochemists tiy to determine where hydrocarbons begin to be liberated and how their quantity and composition may vaiy with increasing maturity. This is equivalent to evaluating the amount and type of kerogen present m the rocks as well as the maturity... 

The recovery of petroleum from sandstone and the release of kerogen from oil shale and tar sands both depend strongly on the microstmcture and surface properties of these porous media. The interfacial properties of complex liquid agents—mixtures of polymers and surfactants—are critical to viscosity control in tertiary oil recovery and to the comminution of minerals and coal. The corrosion and wear of mechanical parts are influenced by the composition and stmcture of metal surfaces, as well as by the interaction of lubricants with these surfaces. Microstmcture and surface properties are vitally important to both the performance of electrodes in electrochemical processes and the effectiveness of catalysts. Advances in synthetic chemistry are opening the door to the design of zeolites and layered compounds with tightly specified properties to provide the desired catalytic activity and separation selectivity. 

The isotopic composition of carbon in carbonaceous organic material (kerogen) from ancient sedimentary rocks gives information on whether photosynthetic organisms were present during rock formation or not. It can also provide information on biological activities if cellular structures had already been destroyed. Sulphur can be used in a similar way (Schopf, 1999). 

The Murchison meteorite shown in Figure 6.7, like all meteorites, is named after the place from which it was recovered and in this case it is the town of Murchison, Victoria in Australia about 100 km north of Melbourne. The fall occurred in 1969 and was followed by an analysis of the chemical composition in some considerable detail. The Murchison meteorite is a carbonaceous chondrite containing about 2 per cent carbon, some as inorganic carbonates, and some as soluble compounds such as amino acids but the bulk as a macromolecular heterogeneous material referred to as kerogen. 

Combined stable isotope analysis ( C, D, N, has been used successfully in petroleum exploration (Stahl 1977 Schoell 1984 Sofer 1984). The isotopic composition of crude oil is mainly determined by the isotopic composition of its source material, more specifically, the type of kerogen and the sedimentary environment in which it has been formed and by its degree of thermal alteration (Tang et al. 2005). Other secondary effects like biodegradation, water washing, and migration distances appear to have only minor effects on its isotopic composition. 

Kerridge JF (1983) Isotopic composition of carbonaceous-chondrite kerogen evidence for an interstellar origin of organic matter in meteorites. Earth Planet Sci Lett 64 186-200 Kerridge JF, Haymon RM, Kastner M (1983) Sulfur isotope systematics at the 21°N site. East Pacific Rise. Earth Planet Sci Lett 66 91-100... 

Kerridge JF, Chang S, Shipp R (1987) Isotopic characterization of kerogen-hke material in the Murchison carbonaceous chondrite. Geochim Cosmochim Acta 51 2527-2540 Kharaka YK, Berry FAF, Friedman I (1974) Isotopic composition of oil-field brines from Kettle-man North Dome, California and their geologic implications, Geochim Cosmochim Acta 37 1899-1908... 

Redding CE, SchoeU M, Monin JC, Durand B (1980) Hydrogen and carbon isotopic composition of coals and kerogen. In Douglas AG, Maxwell JR (eds.) Phys Chem Earth 12 711-723 Rees CE (1978) Sulphur isotope measurements using S02and SFg. Geochim Cosmochim Acta 42 383-389... 

The similarity of kerogen and trona acids is indicated by their elemental compositions shown in Table I. In both materials the carbon to oxygen ratio indicates the presence of considerable quantities of oxygen functional groups. 

Table I. Elemental Composition of Kerogen and Trona Acids...

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