Stephen R. Larter

Water as an oxygen source for the production of oxygenated compounds (including CO2 precursors) during kerogen maturation

Abstract In order to study the generation of oxygen-rich species which may act as CO 2 precursors, the interaction of sedimentary organic matter and water during hydrous pyrolysis has been investigated using 18 O labelled water. Model compound experiments were conducted with a series of compounds (3,4-dimethylphenol, dodecanoic acid and xanthene) in order to assess their levels of simple homogeneous exchange of oxygen with hot water. While dodecanoic acid underwent extensive oxygen exchange (98%), dimethylphenol underwent restricted oxygen exchange (13%) and xanthene showed no exchange. A comparison of the dimethylphenol model compound experiments in H 2 18 O with dimethylphols generated by Kimmeridge Clay kerogen, under identical conditions, showed marked differences in levels of 18 O incorporation (approx. 13% for the model compound and 40% for the kerogen-derived products) suggesting neogenic phenol formation during hydrous pyrolysis. The implications of this inferred water oxygen addition to sedimentary organic matter during kerogen degradation will undoubtedly affect mass balance calculations of the generation of oxygen-rich species from sedimentary organic matter and thus have a potential impact on mass balance assessments of the generation of CO 2 and its precursors in petroleum basins. The results also have major implications for oxygen mobility between organic matter and water in hydrothermal systems and possibly for lower temperature reactions in petroleum systems.

Biomarker binding into kerogens : evidence from hydrous pyrolysis using heavy water (D2O)

Abstract Solvent-extracted Kimmeridge Clay Formation kerogen was heated to 315°C for 72xa0h in the presence of excess water (H2O) or heavy water (D2O). Hydrocarbons generated from the kerogen during the D2O experiments contained variable amounts of deuterium atoms [0 to as high as 12 deuterium atoms per molecule in the compounds we examined (mean of

Determination of stable carbon (δ13C) isotope systematics foralkylphenols and light aromatic hydrocarbons (BTEX) in petroleum formation waters and co-produced oils

Abstract Solid phase microextraction (SPME) techniques coupled with gas chromatography—isotope ratio mass spectrometry (GCIRMS)were used to determine the stable carbon (δ13C) isotopic compositions of aromatic hydrocarbons (BTEX: benzene, toluene, ethylbenzene and xylenes) and phenol in a small suite of co-produced oils and waters from a North Sea oilfield. The δ13C patterns and the compound profiles observed are consistent with the theory that the concentrations and distributions of BTEX and alkylphenols in oilfield waters can simply be explained by partition equilibrium between oil and water. The large difference in δ13C signatures for phenol compared with benzene and toluene (7–8 %o vs. PDB) in both the oil and water phases strongly suggests that, at least for BTEX and phenols, reversible chemical reactions controlled by master geochemical variables (such as fO2) do not appear to be important at the temperatures of most oilfields.