The Effect Of Oxygen Functions On The Properties Of Bitumen Fractions
Authors: Speight J.G. , Moschopedis S.E. 
Published: March 2010

Various in-situ methods of recovery have been proposed for the Athabasca bitumen which rely on the reaction of the bitumen with an oxygen-containing gas, but the properties of the products are usually ill-defined or, at best; largely speculative. Therefore, methods of introducing oxygen functions into the bitumen have been investigated. Comparisons of the product properties with those of the untreated bitumen are described in order to study the effects of these functions and to evaluate their performance during in-situ recovery.

Introduction

Current methods of bitumen recovery from the Athabasca oil sands are centred around a mining process whereby mined oil sand is conveyed to the plant and bitumen is recovered by hot-water washing, with the bitumen thermally upgraded to a "synthetic" crude oil(1). The mining method is, of course, subject to the limitation of easy access to the deposit through the overburden and as only about 10 per cent of the deposit lies within the economical limit of 150 feet from the surface(1), it is conceivable that, in the foreseeable future, bitumen recovery by in-situ techniques will become a reality.

Thus, it is not surprising that a variety of methods have been proposed, and investigated, for the in-situ recovery of the Bitumen(2). Recognition that the bitumen in the oil sands is too -viscous to flow at reservoir conditions(1) has resulted/in the development of methods that are not usually employed as conventional secondary oil recovery techniques for example, the bitumen is quite mobile at temperatures above 30 °C (formation temperature – 4 °C) and successful application of a combination of forward combustion followed by water flooding (COFCAW) to bitumen recovery has been recorded(3).

Other methods involve flooding the formation with aqueous solutions(3) and one method in particular, which involves fracturing the formation between two spaced wells add flushing the bitumen out of the formation using steam and dilute aqueous alkali, was recognized as having the disadvantage that recovered materials periodically plug the formation adjacent to the production well(4). Following from this, an in-situ method has been proposed which requires: initial contact of the bitumen in the formation with an oxidizing gas and subsequent treatment with alkaline solutions of sulphites and/or bisulphites(2). The resulting water-soluble bituminous derivatives were successfully applied to the removal of part of the bitumen from packed columns of oil sand(2).

The course of the reaction of the bitumen with an oxygen-containing gas is extremely complex(5,8), but there are indications(9,10) that, in addition to the formation of higher-molecular-weight material by condensation esters, other oxygen functions, such as carbonyl, carboxylic and hydroxyl groups, are formed in the bitumen. The major introduction of oxygen functions occurs in the higher molecular-weight fractions(9–11) and it therefore seemed worthwhile to study the effects of these particular oxygen functions on the properties of the asphaltenes.

Methods of introducing oxygen functions into bitumens, without severe oxidative degradation, are limited and subject to uncertainty and speculation(12,13). However, coals and humic acids react with diazonium salt(14,15), although, in contrast, asphaltenes have been reported to be inert towards diazonium salts(14,15)

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