ABSTRACT

A series of crude oils and condensates from the Beaufort-Mackenzie Basin has been examined for distribution of the biological marker compounds, steranes and triterpanes. It has been shown that, although some of the oils have suffered extensive biodegradation, the distribution of steranes and triterpanes has remained virtually unaltered. Where such distributions have been altered by extreme biodegradation (e.g. Adgo oil), oil-oil correlations are still possible.

On the basis of the biological marker distributions the oils have been categorized into three main groups. All the oils in the Lower Cretaceous reservoirs, two oils in Paleozoic reservoirs (West Atkinson L-17 and Mayogiak), and one in a Tertiary reservoir (Wagnark C-23), located on the southern and eastern flanks of the basin, belong to one group and have a common marine source derivation.

Oils from Parsons/Siku and Kamik, in Lower Cretaceous reservoirs, and also located on the edge of the basin, are grouped and have a common source which is terrestrial in character.

Oils in Tertiary reservoirs (with the exception of Wagnark) from the more central part of the basin are terrestrial in character and are grouped on the basis of novel triterpane distributions, i.e. they contain 18(H)-oleanane and unusual bisnorlupanes. These oils can be further subdivided on the basis of maturity.

GEOCHIMIE DES REPERES BIOLOGIQUES DANS LES PETROLES BRUTS DE LA REGION BEAUFORT-MACKENZIE, ARCTIQUE CANADIEN

RESUME

Une serie de petroles bruts et de condensats du bassin Beaufort-Mackenzie furent analyses afin de determiner la repartition des composes reperes biologiques, steranes et triterpanes. On demontrent que meme lors de biodegradation avancee, la distribution des steranes et triterpanes demeure presque inchangee. Lorsqu'une biodegradation extreme modifie enfin cette repartition (e.g. brut d'Adgo), les correlations entre bruts s'averent neanmoins possibles.

On classe en trois groupes ces petroles bruts a partir des reperes biologiques. Tous les bruts issus de reservoirs d'age Cretace inferieur, deux bruts de reservoirs d'age Paleozoique (West Atkinson L-17 et Mayogiak) ainsi qu'un brut d'un reservoir d'age Tertiaire (Wagnark C-23), situes sur les flancs sud et est du bassin, s'appartiennent au meme groupe et affichent une meme origine marine.

Les bruts de Parsons/Siku et Kamik, de reservoirs d'age Cretace inferieur et situes aussi sur le perimetre du bassin, se regroupent et proviennent d'une source commune d'aspect terrestre.

Les bruts de reservoirs d'age Tertiaire (a l'exception de Wagnark) du centre du bassin affichent un caractere terrestre et se classent a partir des distributions de novel triterpane. Ils renferment donc du 18 < (H)-oleanane et des bisnorlupanes inusites. Ces huiles peuvent etre subdivisees a nouveau en vertu de leur maturite.

Traduit par Jean Pelletier