Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane

Shale-gas resource plays can be distinguished by gas type and system characteristics. The Newark East gas field, located in the Fort Worth Basin, Texas, is defined by thermogenic gas production from low-porosity and low-permeability Barnett Shale. The Barnett Shale gas system, a self-contained source-reservoir system, has generated large amounts of gas in the key productive areas because of various characteristics and processes, including (1) excellent original organic richness and generation potential; (2) primary and secondary cracking of kerogen and retained oil, respectively; (3) retention of oil for cracking to gas by adsorption; (4) porosity resulting from organic matter decomposition; and (5) brittle mineralogical composition. The calculated total gas in place (GIP) based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf/section (5.78 × 10 9 m 3 /1.73 × 10 4 m 3 ). We estimate that the Barnett Shale has a total generation potential of about 609 bbl of oil equivalent/ac-ft or the equivalent of 3657 mcf/ac-ft (84.0 m 3 /m 3 ). Assuming a thickness of 350 ft (107 m) and only sufficient hydrogen for partial cracking of retained oil to gas, a total generation potential of 820 bcf/section is estimated. Of this potential, approximately 60% was expelled, and the balance was retained for secondary cracking of oil to gas, if sufficient thermal maturity was reached. Gas storage capacity of the Barnett Shale at typical reservoir pressure, volume, and temperature conditions and 6% porosity shows a maximum storage capacity of 540 mcf/ac-ft or 159 scf/ton.

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Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment

The second edition of The Biomarker Guide is a fully updated and expanded version of this essential reference. Now in two volumes, it provides a comprehensive account of the role that biomarker technology plays both in petroleum exploration and in understanding Earth history and processes. Biomarkers and Isotopes in the Environment and Human History details the origins of biomarkers and introduces basic chemical principles relevant to their study. It discusses analytical techniques, and applications of biomarkers to environmental and archaeological problems. The Biomarker Guide is an invaluable resource for geologists, petroleum geochemists, biogeochemists, environmental scientists and archaeologists.

The Biomarker Guide

Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

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Carbon capture and storage (CCS): the way forward

Organic geochemical proxies of paleoceanographic, paleolimnologic, and paleoclimatic processes

Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation—Isotope evidence

The hydrogen and carbon isotopic composition of methane from natural gases of various origins

Natural gases can be characterized genetically using four properties: C2+ concentration, carbon and hydrogen isotope variations in methane, and carbon isotope variation in ethane. Three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters. In these diagrams, compositional fields have been defined for primary gases (biogenic, thermogenic associated, and thermogenic nonassociated) and for gases which result from mixing of these gases. These fields are strictly empirical and comprise compositional variations found in about 500 natural gases. The isotopic and compositional variations in natural gases can be described in terms of (1) processes during formation of the gases such as bacterial fermentation or maturation of organic matter, and (2) processes during secondary migration. Mixing of primary gases is an important and common process. Migration of gases predominantly affects the C2+ concentration, whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged, allowing an assessment of the origin of migrated gases and properties of their source rocks. The formation of gas from humic organic matter and coals is not yet clear from published data. The diagrams use data from various basins and areas. Interstitial gases from the Gulf of California are entirely of bacterial origin: traces of thermogenic gases are formed only in the vicinity of dolerite sills; gases in the south German Molasse basin and in the Vienna basin are of bacterial, mixed, and thermogenic origins. Data from the north Italian Po basin provide examples for genetic characterization of migrated gases.

Martin Schoell

Papers

Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation—Isotope evidence

The hydrogen and carbon isotopic composition of methane from natural gases of various origins

Genetic characterization of natural gases

Multiple origins of methane in the Earth

Fractionation of carbon and hydrogen isotopes by methane-oxidizing bacteria