Geochemical Reaction Proxies (Parameters) to Remotely Monitor In Situ Chemical Reactions and Assess the Extent of Bitumen Upgrading during Thermal Recovery Processes
Creators: name: Koksalan, Tamer
Publisher: name: Graduate Studies
Year: 2013
Subjects: subject: Geochemistry
subject: FOS: Earth and related environmental sciences
subject: Geology
subject: Engineering--Petroleum
subject: geochemical
subject: proxy
subject: CSS
subject: SAGD
subject: Biodegradation
subject: HT-SIMDIS
subject: Oil
subject: GC-MS
subject: reaction
subject: naphtha
subject: VGO
subject: vacuum
subject: residue
subject: maturity
subject: Thermal

description: Elevated temperatures and pressures in combination with the possible catalytic effect of rock matrix during thermal recovery processes could cause significant changes in the physical and chemical properties of the heavy oil and bitumen. A series of simulated thermal recovery experiments, under steam present conditions at temperatures of 300°C and 350°C and for up to 21 days, using oils sands where the residual bitumen (Athabasca and Peace River) was at different levels of biodegradation, were performed in the laboratory. The main goals were to; (a) examine the influence of thermocatalytic and water mediated reactions on the geochemical conversion of hydrocarbon compounds, (b) determine the potential for geochemical reaction proxies (parameters) to remotely monitor (i) in situ chemical reactions to assess the extent of bitumen upgrading and (ii) steam chamber growth during thermal recovery processes such as Cyclic Steam Stimulation (CSS) and Steam Assisted Gravity Drainage (SAGD) by which steam and/or catalysts are involved in the conversion of heavy oil and bitumen. The molecular studies of the bitumen extracted from horizontal well cutting samples and from core representing an individual oil column from the Peace River study area exhibit small compositional changes on lateral scales and large scale compositional and fluid property variations on the vertical scale, with several hydrocarbon compounds progressively altered and/or removed towards the oil-water-contact caused by the biodegradation process. Simulated thermal recovery results suggest that temperature and heating time are the dominant control for depleting hydrocarbon compounds and yields. Higher depletions and yields occur with longer heating time and dramatically increasing depletions and yields during simulated thermal recovery experiments performed at 350°C. The amount and properties of hydrocarbons formed during thermal reactions are also influenced by the nature of the original starting composition of the oil with the more biodegraded oil contributing to higher yields. Results suggest that thermal stress leads to significant changes in the oil composition with vacuum residue, higher end vacuum gas oil fractions and concentrations of heavy hydrocarbons such as steranes, terpanes and mono- and triaromatic steroid hydrocarbons decreasing, whereas naphtha, atmospheric distillate, lower end VGO fractions and lighter hydrocarbons such as n-C9 to n-C17 alkanes, isoprenoid alkanes, naphthalenes, phenanthrenes, anthracenes, dibenzothiophenes increasing. Established reaction proxies, which are a variety of molecular ratios used in geochemical source rock evaluation procedures, concentration data and vacuum residue fraction show strong correlation with the direction of thermal stress (alteration), suggesting they may be employed to remotely monitor (a) in situ chemical reactions to assess the extent of thermal alteration of heavy oil and bitumen, thus bitumen upgrading, (b) steam chamber growth, using produced oil composition during thermal recovery processes such as CSS and SAGD. Results also indicate that, without the involvement of catalysts, temperatures of at least ~320-330°C during thermal processes are needed to reach the initiation threshold for significant cracking reactions and light hydrocarbon generation, thus permanent reduction of oil viscosity. The field application of this important work will allow companies to alter their operating practices to increase recovery of a better grade of bitumen, faster, and at a lower cost than was previously possible.