Carbon and hydrogen isotopic compositions of n -alkanes as a tool in petroleum exploration

Abstract

Compound-specific isotope analysis (CSIA) of individual organic compounds is a powerful but underutilized tool in petroleum exploration. When integrated with other organic geochemical methodologies it can provide evidence of fluid histories including source, maturity, charge history and reservoir processes that can support field development planning and exploration efforts. The purpose of this chapter is to provide a review of the methodologies used for generating carbon and hydrogen isotope data for mid-and high-molecular-weight n-alkanes.We discuss the factors that control stable carbon and hydrogen isotope compositions of n-alkanes and related compounds in sedimentary and petroleum systems and review current and future applications of this methodology for petroleum exploration. We discuss basin-specific case studies that demonstrate the usefulness of CSIA either when addressing particular aspects of petroleum exploration (e.g. charge evaluation, source rock-oil correlation, and investigation of maturity and in-reservoir processes) or when this technique is used to corroborate interpretations from integrated petroleum systems analysis, providing unique insights which may not be revealed when using other methods. CSIA of n-alkanes and related n-alkyl structures can provide independent data to strengthen petroleum systems concepts from generation and expulsion of fluids from source rock, to charge history, connectivity, and in-reservoir processes.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.Petroleum geoscientists use organic geochemistry as an essential tool in oil and gas exploration and field development planning. Relatively low-cost, high-throughput bulk data are commonly used to screen for source rock quality (e.g. per cent total organic carbon (%TOC), hydrogen and oxygen indices) and thermal maturity (Tmax, vitrinite reflectance equivalent). More in-depth geochemical analytical techniques are used in the context of full fluid and reservoir properties to correlate source rocks and reservoir oils, to determine fluid generation and migration history, including presentday reservoir connectivity, and to understand in-reservoir processes, such as biodegradation of in-reservoir oils. These tools are especially powerful when coupled with other measurements made during the exploration and development process, such as compositional analysis during drilling, downhole fluid analysis and other wireline measurements, and pressure, volume, temperature (PVT) and chemical analyses, integrated in the context of geological static and reservoir dynamic models.Molecular biomarkers have been employed in petroleum exploration for several decades (Peters et al. 2005). The usefulness of bulk stable isotope measurements of gases and oils was well demonstrated in the petroleum industry through the decades of the 1970s and 1980s (Stahl 1977;Schoell 1984;Sofer 1984). However, the use of compound-specific isotopic composition of light hydrocarbons, alkanes and biomarkers is less common....

Geochemical applications in petroleum systems analysis: new constraints and the power of integration

“…Recent advances in established techniques, such as compound specific isotope analysis, may finally provide a path to constraining such systems. Pedentchouk & Turich (2017), in this volume, review the history of compound-specific carbon and hydrogen isotope analysis of hydrocarbons, and how such data can be used in exploration activities. They provide several case-study examples of how this technique has been used to better understand the origin of hydrocarbons in systems where conventional molecular geochemistry alone may not provide unambiguous results.…”

“…Techniques and approaches presented herein focus on addressing three key hydrocarbon systems issues: (1) source-rock identification and the temperature/ timing of hydrocarbon generation Gao et al 2017;Pedentchouk & Turich 2017;Stolper et al 2017); (2) the mechanisms and timescales associated with hydrocarbon migration, trapping, storage and alteration Moore et al 2018); and (3) the impact of fluid flow on reservoir properties (MacDonald et al 2017).…”

“…Gilfillan et al 2009). Finally, the isotopic approaches described in Eiler et al (2017), Gao et al (2017), Pedentchouk & Turich (2017) and Stolper et al (2017) all have the capability to elucidate the origin of hydrocarbons in the environment.…”

Derivatization‐free method for compound‐specific isotope analysis of nonexchangeable hydrogen of 4‐bromophenol

“…Since the 1990s, compound-specific isotope analysis (CSIA) has evolved into a mainstream tool in environmental chemistry, bio-and geoscience. [1][2][3] CSIA combines chromatography (usually, gas chromatography, GC) for separation of individual compounds present in the sample (e.g., organic contaminants in groundwater, fatty acids in biological samples or individual hydrocarbons in crude oil) with various variants of mass spectrometry, for measurement of isotope ratios of the separated compounds. In this paper, we present a novel method for CSIA of the hydrogen isotope ratios of a brominated anthropogenic contaminant, 4-bromophenol (4BP), contributing to a study of the biodegradation of this compound.…”

Determination of the δ2H values of high molecular weight lipids by high‐temperature gas chromatography coupled to isotope ratio mass spectrometry

“…exploited. Another potential application arises from very long-chain n-alkanes that are major constituents of crude oil; their δ 2 H values could be used to assess source rock potential 17,18,38,39 , or for correlating different oils and source rocks 38,40 .…”