Isotopic and Molecular Studies of Biodegraded Oils and the Development of Chemical Proxies for Monitoring In Situ Upgrading of Bitumen.

摘要

The world oil inventory is dominated by heavy oils and oil sands bitumens generated almost entirely by the process of biodegradation of conventional oil. This study uses geochemical and isotopic tools to assist in addressing some of the technical challenges in the more efficient and environmentally friendly recovery of these heavy and extra-heavy oil reserves. In particular, the study aimed to develop and assess chemical routes to using the composition of produced oils as a means of assessing temperature and sources of hydrogen in an in situ reservoir reactor during heavy oil recovery.;Two main chemical proxies for monitoring in situ upgrading of heavy oil and bitumen were assessed: oil molecular transformation during non-catalytic and catalytic upgrading and hydrogen isotope systematics for assessing hydrogen transfer between oil and water/H2. When oil sand samples were heated under simulated in situ non-catalytic and catalytic upgrading conditions, i.e. under hydrous pyrolysis and hydrocracking conditions, the generation of a significant amount and variety of new or neoformed hydrocarbons were evident. These included compounds that had been removed by severe biodegradation and also newly generated compounds that appear to be authentic thermal stress indicators under process conditions. The first group of compounds included nalkanes, alkylcycloalkanes, alkylbenzenes, alkyltoluenes and polycyclic aromatic hydrocarbons. The second group was mainly comprised by alkylanthracenes. The generation of the latter is proposed as suitable proxy to track process oil temperature histories during recovery operations. Heating experiments with hydrogen labelled water and hydrogen gas were also conducted. These indicated that variations in delta2H values of oil fractions of produced oil may also be used as a proxy for monitoring temperatures and the sources of hydrogen during in situ non-catalytic and catalytic upgrading operations. The study has significant implications for the development of recovery strategies for heavy and extra-heavy oil reserves. For example: (1) understanding the generation and distribution and production of newly formed pollutants aids in reducing environmental impacts and design of clean up facilities, and (2) understanding the variability of oil quality in individual reservoirs assists in assessing well placements and more suitable recovery methods.;This thesis combines studies of native oil reservoirs and laboratory simulations of upgrading processes. The Alberta basin constituted the study area. The molecular and isotopic studies of the heavy oil and oil sand bitumen across the Alberta basin showed that the severe biodegradation process caused a high variability in the molecular composition of oils. This is seen regionally and locally, with increasing biodegradation occurring with increasing depth of individual oil columns, with several hydrocarbon groups being progressively removed, synchronously but at different rates of biological alteration. Not only hydrocarbons components, but also polar non-hydrocarbon compounds were found to be altered by biodegradation. Despite this, delta34S and delta15N values of whole oil proved to be unaffected by the severe biodegradation process. This confirms that sulfur and nitrogen isotopic signatures can be used in very degraded oils as stable source signatures.