Hydrogen isotope type‐curves of very hot crude oils

Abstract

Several crude oil accumulations in the Pannonian Basin are trapped in uncommonly hot (>170°C) reservoirs. Their maturities range from mature to very mature on the basis of cracking parameters of their biological marker homologous series (ratio of products to reactants). A stable carbon isotopic study of these oils, poor in biological markers commonly used for correlation purposes, did not provide a reliable oil-to-oil correlation. As an alternative tool, the hydrogen isotope compositions of oil fractions separated on the basis of different polarities were measured, and hydrogen isotope type-curves were generated for a set of mature to very mature crude oil samples. This method of presenting hydrogen isotope composition of fractions as type-curves is novel. Nineteen samples (17 crude oils from SE-Hungary, 1 oil condensate and 1 artificial oil) were chosen for the present study. The aim was to examine the applicability of hydrogen isotope type-curves in oil-to-oil correlation and to test the simultaneous application of carbon and hydrogen isotope type-curves in the field of petroleum geochemistry. We have shown that, although the conventionally used co-variation plots proved to be inadequate for the correlation of these hot and mature oils, the simultaneous use of carbon and the newly introduced hydrogen isotope type-curves allows us to group and distinguish oils of different origins.

The effect of oil expulsion or retention on further thermal degradation of kerogen at the high maturity stage: A pyrolysis study of type II kerogen from Pingliang shale, China

“…Oil fractions are expected to be increasingly enriched in 13 C and D in the order asphaltenes > resins > aromatics > saturates (Stahl, 1978), although carbon isotopic compositions of oil fractions in natural samples could display more complicated variations (Fekete et al, 2009). The oil expulsion process generally leaves residual bitumen in the kerogen with more NSO compounds than in the expelled oils and aromatics are more retained in kerogen than the saturates (Sandvik et al, 1992;Ritter, 2003;Kelemen et al, 2006a).…”

H and C isotope trends and anomalies in hot and mature oils from the Pannonian Basin

“…The results are given in the conventional δ value (δ = (R sample /R standard )*1000, where Rsample and Rstandard are the D/H and 13 C/ 12 C ratios in the sample and standard, respectively) relative to V-SMOW (H) and V-PDB (C) in ‰. Based on sample reproducibility and differences in δD and δ 13 C values obtained for standards from their theoretical values, the results are accurate at ±3‰ for δD and better than ±0.1‰ for δ 13 C. See Fekete et al (2011) for detailed description.…”

“…Oil traces of the Makó-Hódmezõvásárhely-trough (M-H-trough), Pannonian Basin have been studied recently (Fekete et al 2009(Fekete et al , 2010(Fekete et al , 2011. The isotope typecurves formed from the stable carbon and hydrogen isotope compositions of different oil fractions were found to be good tools to group these oils of different origins.…”

“…Ten of the fifteen samples was investigated former (Fekete et al 2011). Our aim is to present the isotopic features of high temperature oils (from 170°C to 215°C) and we also try to briefly interpret the effects of the extreme reservoir conditions.…”

Isotopic compositions and biomarkers in crude oils from the Tarim Basin: Oil maturity and oil mixing

“…Hydrogen isotopic analysis may provide further information about oil genesis. dD values of total oils and their fractions were used in characterizing the oil source and mixing (Yeh and Epstein, 1981;Peters et al, 1986;Santos Neto and Hayes, 1999;Fekete et al, 2009). During the past decade, compound specific hydrogen isotopic analysis, which is the same as the carbon isotopic approach, achieved its great potential for use in various fields of petroleum geochemistry, including tracing oil source (Li et al, 2001;Schimmelmann et al, 2004;Dawson et al, 2007;Aboglila et al, 2010), elucidating the depositional environment of source rocks (Li et al, 2001;Schimmelmann et al, 2004;Dawson et al, 2005), determining maturity (Radke et al, 2005;Dawson et al, 2007), and evaluating the impact of biodegradation on oils Asif et al, 2009).…”