D.W. Bennion

Low-Temperature Oxidation Kinetic Parameters for In-Situ Combustion Numerical Simulation

The principal objective of this study was to provide low temperature oxidation (LTO) reaction models which are suitable for use in numeric simulators in in situ combustion for bitumen and heavy oil reservoirs. A systematic study was conducted to investigate the LTO reactions of the liquid phase components of bitumen and heavy oils. Kinetic models are established for the liquid phase reaction components involved in the LTO reactions of a mixture of complex hydrocarbons. Based on the experimental kinetic data, 2 main types of reaction models are proposed. There are (1) a nonsteady state kinetic model to represent the overall rate of oxygen consumption, and (2) 4 nonsteady multiresponse kinetic models representing the oxidation reactions of the liquid phase components. 18 references.

Thermal Cracking Models For Athabasca Oil Sands Oil

The prime purpose of this work was to provide thermal cracking reaction models which can be incorporated into numerical simulators of thermal recovery processes for the Athabasca oil sands. Athabasca bitumen, free of water and minerals, was thermally cracked at constant temperatures in a closed system under an inert atmosphere. The products of cracking were separated into 6 pseudo components: coke, asphaltenes, heavy oils, middle oils, light oils, and gases. Experimental runs were made over temperature range from 303/sup 0/C to 452/sup 0/C. Three series of runs were made at 360/sup 0/C, 397/sup 0/C, and 422/sup 0/C in which the reactions were terminated at various degrees of cracking. For these runs, reaction time vs. product concentration curves were obtained for the above 6 pseudo components. Several pseudo reaction mechanisms are proposed to simulate the experimental results. The reaction rate constants were represented by an Arrehnius-type expression; the activation energies and corresponding frequency factors were determined for each reaction mechanism proposed. (23 refs.)

New Insights Into Enriched-Air In-Situ Combustion

This paper presents the results of 10 enriched-air in-situ combustion-tube tests performed on core from the Athabasca oil sands deposit. The tests show that at high pressures, the use of oxygen-enriched air results in increased low-temperature reactions between the oxygen and the oil, resulting in an increased fuel load and decreased burn stability. Although water injection may enhance the performance of oxygen combustion, it may also lead to increased oxygen storage in the swept zone.

Effect Of Relative Permeability On The Numerical Simulation Of The Steam Stimulation Process

Thermal numeric simulators have been used to predict the performance of the steam stimulation processes. The experience is that room temperature relative permeability curves measured on extracted core samples need to be adjusted to match field performance. This work describes a study which was conducted to observe the effects of temperature on initial water saturations and residual oil saturations. A preserved core was mounted, stressed back to reservoir conditions and saturated with live reservoir oil, then waterfloods and oil floods were run at reservoir and elevated temperatures. Two single cycle simulations were run. Both sets of simulations used temperature functional relationships for the residual oil saturations and connate water saturations. The simulation which used the preserved core relative permeabilities resulted in matching the water production much closer than the simulation using extracted core relative permeabilities. 14 references.

The thermal behavior of vertically-operated near-adiabatic in-situ combustion tubes

Abstract A commonly used approach for studying in-situ combustion processes has employed vertically-operated adiabatic combustion tubes. The data obtained from such apparatus are sometimes subject to interpretation problems because of convective circulations in the annulus, which are induced by the operation of the guard heaters. The main objective of this study was to systematically investigate the operational domain and impact of these convective heat transfers, and, in general, to provide a comprehensive framework for interpreting such experimental data. A microcomputer-based system was developed to automate the operation of the guard heaters and to provide a record of the power outputs of each heater with time. The automated system was used to gather data from five combustion experiments in which operating pressure, injected oxygen concentrations, water/oxygen ratio, and the type of gas in the annulus were varied. The experimental results showed that thermal energy from the heaters, as they responded to the combustion front, was transported upward by convection in the annulus. This energy elevated temperatures in the core behind the front. The tendency for annular convection to occur was found to increase with operating pressure, the on-time of the heaters, and with the Rayleigh number of the gas used in the annulus. Also, as the severity of convection increased there was (a) a reduction in the thermal efficiency of the heaters, and (b) an overall increase in heat loss from the combustion zone which required higher oxygen fluxes in order to avoid declining peak temperatures and to improve oxygen utilization. An analysis of the thermophysical properties of the annulus gases used explained these experimental observations, and demonstrated that gases of lower thermal conductivity may not necessarily reduce heat loss from the combustion tube.

Using Combustion Tube Data To Tune A Numerical Simulation

Using the Computer Modelling Groups ISCOM simulator, 3 Athabasca Oil Sands combustion tube tests were matched: 2 wet combustion tests with water-air ratios of 6.91 and 2.25 kg water/cu m (ST) air and dry test. In this work, laboratory measurements of oil viscosity, density, and thermal cracking kinetic parameters, as well as a description of the crude oil characterization technique employed are presented. The simulated results, using the above data and characterization, compared well with the experimental runs. The only problem area pertained to matching the superheated steam bank in the second wet combustion run. A quantitative comparison between empirical and simulated temperature profiles, production histories, and fuel lay-down is included. 11 references.

In-situ combustion process study with a combined experimental/analytical approach

Analysis of combustion-tube data produced from experiments performed under realistic reservoir conditions is currently the most valid method of investigating the in-situ combustion process. Description of an approach that uses a differential moving-frame descriptive model to analyze data from stabilized combustion processes produced in combustion-tube experiments. The approach is applied to a set of dry-air combustion runs. This study revealed consistent values for the fuel-combustion-reaction-kinetics parameters and gave insight into the relationship between injected-gas flux and the distribution of energy liberation rate with implications for process stability

COMPARISON OF ENRICHED AIR AND NORMAL AIR IN SITU COMBUSTION

ABSTRACT The application of enriched air (oxygen) in situ combustion as a thermal recovery process for both heavy and conventional oils has a number of theoretical advantages over normal air combustion. The reservoirs for which enriched air combustion broadens the scope of application are those with low injectivity and those for which sand errosion of the production wells is a major operating problem. Enriched air combustion, with the high concentrations of produced carbon dioxide, also shows potential as a tertiary recovery process for those reservoirs which are sufficiently confined to allow for operation above the minimum miscibility pressure, providing sufficient fuel remains for the process. This paper will compare enriched air and normal air in situ combustion based on literature and laboratory combustion tube tests. It will discuss the theoretical advantages and disadvantages of oxygen combustion with regard to the observed laboratory behavior.