This paper was presented at the 2000 CSPG conference in Calgary.

Late Jurassic Source Rocks in the northern Flemish Pass Basin, Grand Banks of

Newfoundland

Jock N. McCracken* (Petro-Canada, P.O. Box 2844, Calgary, AB T2P 3E3 jmccrack@petro-

canada.ca),

Annemone Haager (Target GeoConsulting Ltd.), Ken I. Saunders (Petro-Canada) and Byron W.

Veilleux (Petro-Canada)

Recent expansion of exploration on the Grand Banks, Newfoundland, requires consideration of

the nature, distribution, and potential of petroleum source rocks. For the Jeanne d’Arc Basin, an

established petroleum province, (approximately 2 billion barrels recoverable, discovered to

date) the Late Jurassic (Kimmeridgian) Egret Formation has been identified as the contributor to

fields at Hibernia, Terra Nova, Hebron, and Whiterose. From geochemical and geophysical

evidence, this paper proposes that the Late Jurassic organic-rich beds reach northeastward,

approximately 100 km, from the Jeanne d’Arc Basin to the northern Flemish Pass Basin, thereby

enhancing the petroleum potential of that tectonic region.

Approximately 1.1 million hectares (8 exploration blocks) in the Flemish Pass Basin were made

available to industry in 1998 and 1999. Only 4 wells were drilled in this extensive and remote

area. One of these wells, Esso PAREX et al Baccalieu I-78, drilled to 5135 m in 1985, was key to

establishing the existence of the critical petroleum system. This well was drilled with an invert

emulsion drilling fluid using Esso Sarnia A DMO base oil. It is well known that the effects of oil

based mud on the geochemistry analysis can be unpredictable. Biostratigraphic data and Rock

Eval analysis indicated a thick source rock interval at this location. It was fortunate that an 18 m

core was cut within these source rock beds so the geochemistry could be reanalyzed and

calibrated.

This cored interval was sampled and analyzed by detailed organic geochemistry. Rock Eval

resulted in TOC ranging from 0.92 to 4.83% (average 2.1%) and HI ranging from 109 to 510

(average 355 mg HC/g TOC). Thus the majority of the samples can be classified as type II

kerogen bearing marine source rocks. Based on the Genetic Potential (S1+S2) this interval

contains excellent source rocks for oil. Tmax values are between 428 and 449 o C with an

average of 438 o C. Since 430 o C marks the onset of hydrocarbon generation, we can say that

these samples have reached the early stage of oil generation. Twelve samples were selected for

Soxhlet extraction, then fractionation by liquid chromatography and analysis by capillary gas

chromotography and gas chromotography-mass spectrometry. Eight of the investigated

samples had extract yields ranging from 1247 to 3779 ppm and hydrocarbon yields between

991 and 2770 ppm both indicating excellent source rock potential. The samples from the

Baccalieu core are shown to be genetically related in general to Jeanne d’Arc Basin oils from the

biomarker analysis. The Baccalieu source beds are at a lower level of maturity than Jeanne

d’Arc Basin oils. In conclusion, there was no indication that the oil based drilling fluid had

contaminated these source rocks and that the source rock component in the risking equation

was accordingly adjusted.

The Baccalieu I-78 well lies about 100 km NE of a cluster of Jeanne d’Arc Basin wells (Lancaster

G-70, South Tempest G-88, South Merasheen K-55, North Dana I-43, and Panther P-52) all of

which penetrated Kimmeridgian source beds. Those wells lie along a prominent NE-trending,

linear, gravity and magnetic anomaly that reaches the Flemish Pass Basin (and the Baccalieu

well). We suggest that the anomaly represents a continuous basin trend of Cretaceous, Jurassic

and perhaps older sediments, along which Late Jurassic deposition localized the organic-rich

facies.

Biographical Information:

Jock McCracken is a geologist with the Grand Banks Asset Team at Petro-Canada. He has been

involved in exploration for 19 years, with the first 16 years at Mobil Oil Canada. His experience

has been principally with Grand Banks exploration as well as in the Scotian Shelf, North Sea and

onshore and offshore basins in China.