GEOSYNTHESIS OF ORGANIC-COMPOUNDS .1. ALKYLPHENOLS

Methylation, isopropylation, and sec-butylation are proposed as geosyn thetic processes to account for the alkylphenol compositions of crude oils with phenol distributions dominated by ortho and para substituted compounds. Phenol distributions in eleven crude oils and four kerogen pyrolysates were analysed using GC-MS (gas chromatography-mass spectr ometry). Ten of the crude oils show high relative abundances of ortho and para substituted phenol isomers and some were also enriched in C-3 -C-5 alkylphenols compared to the kerogen pyrolysates. Because the dis tributions of products obtained from the laboratory alkylation of cres ols closely resemble those of phenols in these crude oils, we propose that similar alkylation processes occur in source rocks. Alkylation ra tios reflecting the degree of methylation, isopropylation, and sec-but ylation, which were based on the relative abundance of the dominant al kylation products compared to their likely precursor ortho-cresol, ind icate that high levels of methylation occurred in crude oils over a wi de range of maturities, whereas high levels of isopropylation and sec- butylation were observed only in mature samples. Dissolution of the ph enols in crude oils by water contact was discounted as an explanation for the observed phenol distributions based on the relative distributi on coefficients of phenols between a hydrocarbon phase and water.