Chris Parry

OPENING OF THE NORTH ATLANTIC

BASIN – LESSONS FROM THE SOUTH

Talk Outline

Upper Plate, Lower Plate Conjugate Margins.

North Atlantic Fracture Zone:

Continental Crust Morphologies,

Svalbard Upthrust Zone.

South Atlantic Fracture Zones:

Non Rigid Plates,

Continental and Oceanic Crust Morphologies,

Controls on Hydrocarbon Migration and Reservoir Distribution,

Reactivation of Fracture Zones leads to Complex Trap Geometries.

Key message:

The Fracture Zone/Conjugate Margins of the South Atlantic model can be applied to the North Atlantic to develop new exploration concepts for the Mid-Norway region.

Detachment-Fault Model of Passive Continental Margins

with Upper Plate or Lower Plate Characteristics

Lower Plate: Complex Structure,

Bowed up Detachment Faults,

Wide Continental Shelf.

Upper Plate: Relatively Unstructured,

Underplating Uplift,

Narrow Continental Shelf.

Modified after Lister et al.,1986. Detachment Faulting and the

Evolution of Passive Continental Margins. Geology, pp. 246-250.

Modified after Lowell, J.D.,1972 Spitzbergen Tertiary Orogenic

Belt and Fracture Zone. Geol. Soc. Am. Bull., pp. 3091-3102

Convergent Strike Slip or Transform Motion Upthrust Zone

Eurasian

Plate

North American

Plate

• Two plates moving at low

convergent angle causes space

problem.

• Easiest direction for relief is

upwards.

• Upthrusts are not necessarily

symmetrical.

• Faults coalese and anastomose

with depth.

Pre-Rift configuration of the Atlantic Ocean

Simplified and modified after Torsvik et al., 2010, Plate tectonics and net lithosphere

rotation over the past 150 My. Earth and Planetary Science Letters, 106–112.

African

Plate

North

American

Plate

Eurasian

Plate

African micro plates coloured for emphasis

Western limit

of thick

sedimentary

cover

Meyers et al., 1996

Duval et al., 1991

Lower Plate:

Wide Continental Shelf.

Upper Plate:

Narrow Continental Shelf.

Lower Plate:

Wide Continental Shelf.

Upper Plate:

Narrow Continental Shelf.

Fracture Zones of the South Atlantic

Rio Muni & Gabon Basins: Cretaceous Pre Rift Configuration

Lower

Plate

Upper

Plate

Simplified after Meyers et al., 1996. Deep

penetrating MCS imaging of the rift-to

drift- transition, offshore Douala and North

Gabon basins, West Africa, Marine and

Petroleum Geology, pp.791-835.

200 Km

Pan

Afr

ican

Mo

bile B

elt

Pre-Cambrian basement

Cretaceous rift basins

Transfer fault zone

Modern coastline

Mid Atlantic Ridge

Upper

Plate

Some major fracture zones

originate along pre-Cambrian

structural grain

5 KM

Fracture Zones divide the deep water

into discrete depo-centres with

different fill histories.

Fracture Zones in Oceanic Crust

OCEANIC

CRUST

Basement structural highs related to

volcanic activity along “leaky” fracture

zones in the oceanic crust set up the

initial basin structural framework.

Deepwater sedimentation on-lapped

these basement highs whose influence

continues to propagate into younger

strata by differential compaction.

Reservoir

Source Rock

1.0

Se

co

nd

TW

T

Fracture Zone influence on Deepwater Systems

Shaded Relief Bathymetry Map

Differential Compaction related faults,

related to underlying Fracture Zone

the absence of evidence is not evidence of absence.

1 KM

Equatorial Guinea Ceiba Field, Senonian inversion structure

related to reactivation of Ascension Fracture Zone

Reproduced with permission of C and C Reservoirs

Base Ceiba Canyon Channelized Sands

Southern Miocene Canyon Northern

Miocene

Canyon Top Campanian

Laminated Sands

Vøring Margin - Lower Plate

Wide Continental Shelf,

Complex Structure,

Detachment Faults.

Møre Margin - Upper Plate

Narrow Continental Shelf

Relatively Unstructured,

Underplating Uplift.

Lofoten Margin - Upper Plate

Narrow Continental Shelf

Relatively Unstructured,

Underplating Uplift.

Top Crystalline Basement Depth Structure Map

Ebbing & Olesen, in press.

North Atlantic Conjugate Margins: Norway

500m WD

North Atlantic Conjugate Margins: Norway & Greenland

Vøring Margin

Lower Plate

Møre Margin

Upper Plate

Lofoten Margin

Upper Plate

Upper Plate

Underplating Uplift.

Lower Plate

Wide Shelf,

Lower Plate

Wide Shelf,

Offshore/Onshore Basement Lineament Linkage?

2D False Colour Non Caledonide Basement Geology

N

S

N

3D Combined Magnetics/Basement/Topography

Dip-Azimuth display looking from South

Flower Structure – Vøring Basin

• Two plates moving at low convergent angle causes space problem

(plate reorientation due to opening of Fram Strait?)

• Easiest direction for relief is upwards.

• Wrench fault flower structures are not necessarily symmetrical.

• Faults coalese and anastomose with depth.

MNR05-7495 Courtesy of FUGRO/TGS

Extensional Interpretation

Simple ”basin floor” layer cake stratigraphy

Strong Amplitudes Flat Event

Transtensional Interpretation

Now add complex stratigraphy!

Stacked Strong Amplitudes

Flat Event

Conclusions

A simple symmetric spreading model can be used to explain the opening of the North Atlantic.

NW-SE trending, coast perpendicular fracture zones, are

recognized regionally in the deepwater and adjacent shelf, probably linked to onshore pre-Cambrian basement fabric.

Transtensional, transpressional and inversion structuring

associated with reactivation of the mid ocean ridge transform boundaries/fracture zones is obvious throughout the North Atlantic (as seen in the south).

New exploration models can be developed.

Acknowledgements:

I am grateful to ConocoPhillips management for

their support for the publication of this article

Some Concluding Remarks for Reviving Exploration

”The trained mind will focus on the known, at the expense of the unknown.”

Park A Dickey:

”We usually find oil in new places with old ideas.

Sometimes, also, we find oil in old place with a new idea,

BUT we seldom find much oil in an old place with an old idea.”

Matthew 7:7

”Seek and ye shall find”

Takk for oppmerksomheten!

Wallace Pratt:

”Oil is first found in the minds of men (and women!)”