60th Annual Report on Research 2015

This project is designed to investigate the controlling factors of carbon and hydrogen isotope fractionations between light hydrocarbons (including CO₂) following their generation and/or expulsion from source rocks in sedimentary basins, by conducting a series of laboratory experiments. Despite the wide use of isotope data to understand hydrocarbon generation, fundamental knowledge is still limited on light hydrocarbons and CO₂ during the expulsion of oil and natural gas from source rocks and subsequent migration and accumulation processes, and corresponding hydrogen and carbon isotope partitioning. The objective of this study is to identify the key variables controlling fractionations of carbon and hydrogen isotopes by equilibrium exchange experiments under an array of physical and chemical conditions, including temperature, pressure, mineral compositions, and fluid chemistry (dissolved Cl-). The successful completion of this study will help establish a model describing carbon and hydrogen isotope fractionations between low molecular weight hydrocarbons and CO₂under different conditions encountered in sedimentary basins. This project can be considered basic and fundamental to the understanding of formation and evolution of hydrocarbons in sedimentary basins.

This project gives the PI an opportunity to work in the area of organic and stable isotope geochemistry where my interests are focused, and demonstrate profound commitment to graduate student research as well. It will establish a firm foundation for the PI’s contributions to research and education. The graduate students working on this project are responsible for conducting all proposed experiments under PI’s supervision. They also are involved in chemical and isotope analyses of experimental products and data processing. This project engages them in performing scientific research and learning laboratory/analytical techniques, expand their knowledge base in petroleum geochemistry and benefit their future career. Due to visa issues and subsequent enrollment delay for an international graduate student, however, another graduate student has been working with PI on this project for only 3 months in the first year (see Personnel Report).

As planned in the proposal, the first year studies of this 2-year project largely involves experimental apparatus setup and testing under the range of proposed conditions, material preparations and characterizations, and analytical instrument calibration. The key research work is described as follows:

1) The setup of an experimental apparatus has been completed. It is connected to a high-pressure fluid delivery system (HPLC pump) on the inlet side, and a back pressure regulator on the outlet side to maintain constant pressure. The heating element is a series of heating bands external to the reactor. Temperature control is performed by 3 type-J thermocouples, 2 of which are located inside the reactor. A key aspect of this system is that multicomponent gases along with fluid can be delivered to the reactor at constant flow rates and constant pressures. The 2-position gas injection valve controls the dissolved gas compositions. The test runs under different temperature and pressure conditions will be conducted following the installation of a sample holder inside the reactor.

2) Magnetite and Ni-bearing magnetite, the minerals which will be used in experiments, were synthesized from inorganic compounds in laboratory. Their crystal characterization was confirmed by XRD analysis.

3) The Gas Chromatography - Isotope Ratio Mass Spectrometry (GC-IRMS) system was calibrated for chemical composition and compound specific carbon isotope analyses. The calibration included multiple analyses of standard gas mixes: NIST 8559 and 8561. Repeated analyses have shown that the reproducibility is less than 0.20 per mil.

The studies in year 2 will primarily be devoted to the completion of experimental apparatus setup and experimentation under proposed conditions with subsequent product analysis.