Conclusion

This will be the last note on the blog.

I have chosen the Jeanne d'Arc Basin no without reason.

I wanted to find out a little bit about opening of the Atlantic Ocean and when I was writing the second note I have completed my knowledge about it.

For me the most interesting thing was petroleum resources. Preparing the January note involved broadening my knowledge in petrouleum geology. Right now I know more about structural, sedimentary traps or seals or resource rocks.

I tried to write notes connected with subjects of Paleogeography and Basin Analysis course as much as possible but the availability of free papers about the Jeanne d'Arc Basin was poor.

In the end I want to say that thanks to writing notes in English I have expanded my english geological vocabulary, which is very important to me.

Stay classy and work like crazy, baby! :)

~Weronika

Petroleum Resources of the Jeanne d'Arc Basin

In this note I want to mention a little bit about petroleum resources of the Jeanne d’Arc Basin. 

Hydrocarbon source, migration and trapping

 

It was geochemically traced that the most important and almost exclusive source rock is the Kimmeridgian Egret Member, which I described in November.


The Egret Member occurs all over the Jeanne d’Arc Basin and is buried to depth, which varies from 3300 m and 5000 m. The quality of the source rock is very high, contain oil-prone type I and II Kerogen. The TOC is ranging from 2% to 12%. According to API grades, oils are light and have about 30-35°. This kind of oil is the most desirable from economical point of view. Also heavy oil pools have been discovered. Maturation paths which led to hydrocarbon generation were diverse and that is why maturity is different even in stacked pools within the same field.
Central and northern parts of the basin are overmature, which is connected with gas-prone occurring in these areas (Fig. 1). 

Fig. 1 Egret source maturity map. (from: Enachescu, 2006).

Vertical variations suggest that appeared a few episodes of oil migration and emplacement, which took place between the Mid-Cretaceous till the Early Eocene. Hydrocarbons have migrated:

• vertically (most abundant) along the existing extensional faults.
• laterally along basin flanks

As we know, the HCs move out from source rocks and migrate into reservoir rocks. To stay in this reservoir rock and not move further is necessary trap, which is sealed by impermeable rocks on top and the sides.
The Jeanne d’Arc Basin is rich in rocks which can serves as seals. Oil and gas accumulations in the basin are sealed by thick Late Jurassic to Late Cretaceous shales which constitute among others by the Fortune Bay, White Rose, Dawson Canyon, Nautilus Formations. Another good seal occurring in the basin are Paleogene-Neogene fine-grained clastics from Banquerau Formations.


Structural framework, which has developed during the complicated geological history (rifting, subsidence) of the Newfoundland Margin, had a strong influence on the trapping of the hydrocarbons in the Jeanne d’Arc Basin.


The predominant structural traps occurring in the Jeanne d’Arc Basin are: structural anticlines, faulted anticlines, faults (listric normal, transfer), roll overs, faulted and tilted blocks, folds, transfer folds. Salt induced structures such as pillows, domes, diapirs, allochtonous teardrops also occur.


Sedimentary traps are abundant in the Jeanne d’Arc Basin and most of the discovered fields have this kind of trapping. Sedimentary traps are pinchout, onlap, truncuation, lens.


Reservoirs occur in:


-syn-rift, silicoclastic units (Late Jurrasic to Early Cretaceous): the Jeanne d’Arc, Hibernia, Catalina and Ben Nevis/Avalon Formations (Fig. 2).


-passive, silicoclastic unit (Upper Cretaceous to Eocene), sandstones from the South Mara member belonging to the Banquereau formation (Fig.2).

Fig. 2 Regional geological cross-section (SW-NE) through the Jeanne d'Arc Basin. Main reservoirs are indicated. (from Enachescu, 2006, after: Sinclair, 1994).

The Ben Nevis/Avalon Reservoir

The Avalon/Ben Nevis Reservoir consist of the older Avalon Formation (I described this formation in December) which is uncomformably overlied by the younger Ben Nevis Formation. The Nautilus Formation which occurs above the Ben Nevis Formation consist of siltstones and calcareous shales which provide a great seal. (Fig. 3)

Fig 3. Structural cross section. White Rose area. In this section can be observed the Avalon Formation (reservoir rock), which is covered by the Nautilus Formation (seal). (from: Enachescu, 2006).

Reserves

Total reserves in 18 fields add up to 2,117 MMbbl oil, 5,050 BCF gas, 290 MMbbl condensates. It’s not total amount, researchers estimated that probably 3,3 millions barrels of oil are waiting for discover.


The first discovery (in 1979) and the largest one was in the Hibernia Field. The Hibernia Field is located 300 km to the east, south east from Newfoundland and Labrador. It was estimated that contain 874 million barrels of recoverable oil, which occur in two reservoirs: the Hibernia (Early Cretacous) and The Ben Nevis-Avalon (Aptian-Albian). (Fig.1)

Another very important place is the Whiterose Field, which was discovered in 1984 and is located about 350 km east of Newfoundland and Labrador. This field contain one, very important reservoir: the Ben-Nevis Avalon. (Fig.1)

The Terra Nova Field was also discovered in 1984 and is located near the White Rose field, consist of one reservoir: the Jeanne d’Arc. (Fig. 1)

Table. 1. Oil and gas daily and total annual production in the Jeanne d'Arc Basin from 2005. (from: Enachescu, 2006)

Important terms

MMbbla (million barrels)

1 barrel (bbl)- 42 US Gallons= 35 imperial Gallons= 158,76 litre (volume)

BCF (billion cubic feet)

1 CF = 28.32 litres

Play- it is a larger area with possibly hydrocarbons, a smaller one is called prospect

Seal- is a cap rock, which don’t let hydrocarbons to migrate

API (Amercan Petroleum Institute) gravity- is an indicator, which show how heavy or light is a petroleum liquid in compare to water. The higher the API gravity, the lighter the crude.

Light crude oil: API gravity > 30 °
Normal crude oil: API gravity from 30 ° to 22 °
Heavy crude oil: API gravity < 22 °

TOC (the total amount of organic carbon)

TOC quality (weight in %)
< 0,5 poor
0,5 - 1,0 fair
1,0 - 2,0 good
2,0 - 4,0 very good
> 4,0 excellent

Oil pools- the subsurface traps in which occur petroleum, they are within reservoir rock, can be isolated, or stacked on top of one another, or occur laterally from one another.

Oil field- areas with oil pools.

Bibliography: 

Enachescu, 2010. Petroleum Exploration Opportunities in Jeanne d d’Arc Basin Arc Basin, Call for Bids NL10-01.

Enachescu, 2006. Newfoundland and Labrador, Call for Bids NL06-1. Jeanne d'Arc Basin. 

Spila M., 2005. Application of Ichnology in the Paleoenvironmental Reconstuction and Reservoir Characterization of the Avalon Ben Navis Formations, Hibernia Field, Jeanne d’Arc Basin, Grand Banks of Newfoundland, doctor thesis, University of Alberta/