Assessment of Sweep Efficiency and Breakthrough Using CO2, H2O, Carbon and Hydrogen Isotope Composition in a Water Alternating with Gas EOR Project in Onshore Abu Dhabi, UAE

Measuring sweep efficiency and understanding breakthrough are the most important parameters to assess an Enhanced Oil Recovery (EOR) project having Water Alternating with miscible CO2 Gas (WAG) injection. The objective of this study was to use CO2, H2O and isotope compositions to assess sweep efficiency and breakthrough in producer wells in an ADNOC Onshore field in order to take the necessary actions for project optimization (e.g., injector and/or future producer well location optimization). CO2 and H2O compositions, along with their respective carbon and hydrogen isotopes, was integrated with downhole pressure gauge data to evaluate the impact of WAG operation on EOR. It was understood at the start of the project that an isotopically distinct injected CO2, compared to the oil associated CO2, would assist in the evaluation of sweep efficiency and breakthrough. The injected CO2 used in the WAG comes from a steel mill that is isotopically very distinct (i.e., significantly light) from the oil associated CO2. CO2 and H2O are injected periodically in the reservoir through designated injectors distributed over the field. The initially produced oil associated CO2, H2O, carbon and hydrogen isotope values were available as reference to measure the extent of sweep efficiency and breakthrough. Injected H2O and CO2 compositions and their respective hydrogen and carbon isotope values are measured at each injection cycle (so called campaigns). This is then followed by periodic compositional and isotopic measurements of the same components in oil and water producer wells to measure the extent of breakthrough. CO2, H2O composition and carbon and hydrogen isotope measurements in injector and producer wells indicate that the injected CO2 is preferentially breaking through in certain parts of the field. This indicates heterogeneous reservoir quality distribution throughout the field with better reservoir quality (e.g. higher permeability) between injector and producer wells having faster breakthrough. The compositional and isotopic measurements are sensitive enough to register compositional changes in the producer wells relatively faster than assessed by downhole pressure gauges.

Stable isotope (δD, δ18O) data on the structural water of two sericite samples from the Cu-Au high-sulphidation deposit Chelopech, Bulgaria – a tentative study

The epithermal high-sulphidation Cu-Au Chelopech deposit is characterized by a well-developed and well-traceable hydrothermal footprint manifested in the volcanic host rocks. The economic ore mineralization is embedded in the strong silicification, included among the advanced argillic zone of alteration, smoothly transitioning to quartz-sericite alteration that evolves into widespread propylitics. The quartz-sericite alteration zone is accessible for exploration only in underground mining galleries and exploration drillings. The main mineral assemblage in this zone is quartz, sericite, pyrite, minor rutile/anatase and relics of apatite and feldspar. According to XRD data from the studied samples, sericite was defined as illite and muscovite/sericite 2M1 polytype. The abundance of heavy stable isotopes (D, 18O) in the structural water of two sericite samples is the object of this study. A special attention was paid to the separation of extraneous waters from the structural one by thermal fractionation. The extracted structural water was converted to hydrogen and carbon dioxide before the isotopic measurements. The obtained results, put into a δD vs. δ18O plot, indicate that sericite structural water is “heavier” than meteoric water, within uncertainty limits.

Of herds and societies—Seasonal aspects of Vinča culture herding and land use practices revealed using sequential stable isotope analysis of animal teeth

Late Neolithic Vinča communities, spread over much of central and northern Balkans during the late sixth to mid-fifth millennium BC and characterised by unusually large and densely population centres, would have required highly organised food production systems. Zooarchaeological analysis indicates that domesticate livestock were herded, but little is known about the seasonal husbandry practices that helped ensure a steady supply of animal products to Vinča farming communities. Here, we present new stable carbon (δ13C) and oxygen (δ18O) isotopic measurements of incremental bioapatite samples from the teeth of domesticated livestock and wild herbivore teeth from two late Neolithic Vinča culture sites: Vinča-Belo brdo and Stubline (Serbia). Our results show a low variation overall within sheep and goats in terms of pasture type that may have been composed of seasonal halophyte plant communities, which have higher δ13C values due to the saline rich growing environments. Cattle feeding strategies were more variable and provided with supplementary forage, such as cut branches or leafy hay, during winter. The sharp distinction in the management of cattle and sheep/goat may be associated with the development of herding strategies that sought to balance livestock feeding behaviours with available forage or, more provocatively, the emergence of household-based control over cattle–an animal that held a central economic and symbolic role in Vinča societies.

Presenting the Compendium Isotoporum Medii Aevi (CIMA) and Bayesian Case Studies

The Compendium Isotoporum Medii Aevi (CIMA) gathers more than 50 000 isotopic measurements for bioarchaeological samples located within Europe and its margins dating between AD 500-1500. This volume of isotopic data, together with collected supporting information, offers multiple research opportunities. This is illustrated here using novel Bayesian modelling methods on selected case studies to reconstruct medieval human lifeways (i.e. human subsistence, spatial mobility), animal management practices, and paleo-environmental conditions. We also discuss how the integration of isotopic data with other types of archaeological and historical data can improve our knowledge of historical developments throughout medieval Europe.

Isotopic evidence for the formation of the Moon in a canonical giant impact

Isotopic measurements of lunar and terrestrial rocks have revealed that, unlike any other body in the solar system, the Moon is indistinguishable from the Earth for nearly every isotopic system. This observation, however, contradicts predictions by the standard model for the origin of the Moon, the canonical giant impact. Here we show that the vanadium isotopic composition of the Moon is offset from that of the bulk silicate Earth by 0.18 ± 0.04 parts per thousand towards the chondritic value. This offset most likely results from isotope fractionation on proto-Earth during the main stage of terrestrial core formation (pre-giant impact), followed by a canonical giant impact where ~80% of the Moon originates from the impactor of chondritic composition. Our data refute the possibility of post-giant impact equilibration between the Earth and Moon, and implies that the impactor and proto-Earth mainly accreted from a common isotopic reservoir in the inner solar system.

IsoSolve: an integrative framework to improve isotopic coverage and consolidate isotopic measurements by MS and/or NMR

ABSTRACTStable-isotope labeling experiments are widely used to investigate the topology and functioning of metabolic networks. Label incorporation into metabolites can be quantified using a broad range of mass spectrometry (MS)and nuclear magnetic resonance (NMR)spectroscopy methods, but in general, no single approach can completely cover isotopic space, even for small metabolites. The number of quantifiable isotopic species could be increased, and the coverage of isotopic space improved, by integrating measurements obtained by different methods; however, this approach has remained largely unexplored because no framework able to deal with partial, heterogeneous isotopic measurements has yet been developed. Here, we present a generic computational framework based on symbolic calculus that can integrate any isotopic dataset by connecting measurements to the chemical structure of the molecules. As a test case, we apply this framework to isotopic analyses of amino acids, which are ubiquitous to life, central to many biological questions, and can be analyzed by a broad range of MS and NMR methods. We demonstrate how this integrative framework helps to i) clarify and improve the coverage of isotopic space, ii) evaluate the complementarity and redundancy of different techniques, iii) consolidate isotopic datasets, iv) design experiments, and v) guide future analytical developments. This framework, which can be applied to any labeled element, isotopic tracer, metabolite, and analytical platform, has been implemented in IsoSolve (available at https://github.com/MetaSysLISBP/IsoSolve and https://pypi.org/project/IsoSolve), an open source software that can be readily integrated into data analysis pipelines.