dr andy alvey – badley geoscience prof. nick kusznir ... · the octek team: dr andy alvey –...

The OCTek Team:Dr Andy Alvey – Badley GeoscienceProf. Nick Kusznir – Liverpool UniversityDr Alan Roberts – Badley Geoscience

BADLEY GEOSCIENCE LIMITED www.badleys.co.uk/products/octek.htm

http://www.badleys.co.uk/products/octek.htm

OCTek combines gravity inversion and plate reconstructions to support new ventures exploration strategy and petroleum-systems modelling at deepwater rifted continental margins

The OCTek project (tectonics of the Ocean-Continent Transition) is a collaboration between Badley Geoscience and Prof. Nick Kusznir, leader of the Geodynamics Research Group at Liverpool University

Overview

Studies and reports currently available:• OCTek Atlantic

• OCTek Arctic/North Atlantic

• OCTek Asia-Pacific

• OCTek Indian Ocean

OCTek uses a new gravity inversion technique plus bathymetry and sediment thickness data to produce maps and grids of:

1. Depth to Moho

2. Crust & lithosphere thinning/beta factor

3. Total crustal thickness, incl. volcanic addition

4. Residual continental-crustal thickness

5. Residual thermal gravity anomaly

at global rifted continental margins and their ocean-continent transitions

Overview

Overview

OCTek applies the 3D gravity inversion technique of:

• Greenhalgh & Kusznir (2007, Geophysical Research Letters)

• Chappell & Kusznir (2008, Geophysical Journal International)

• Alvey et al (2008, Earth and Planetary Science Letters)

Available at: www.badleys.co.uk/products/octek.htm

complemented by new plate reconstructions which progressively restore the OCTekcrustal thickness maps back through their sea-floor spreading history to the time of breakup


Key to the OCTek gravity inversion technique is the incorporation into the inversion scheme of:

• The lithosphere thermal gravity anomaly resulting from breakup

• A prediction of new volcanic crustal addition during breakup, leading to the formation of oceanic crust

Published results have shown the importance of incorporating both these parameters in the inversion when investigating deepwater margins

Overview

Input Data• Free air gravity• Bathymetry• Ocean isochrons• Sediment thickness

Outputs• Moho depth• Crustal thickness• Lithosphere thinning factor• Crustal cross-sections

Rifted Margin Crustal Thickness & OCT Location from Gravity Inversion

Bathymetry

Free Air Gravity Ocean Isochrons

Crustal Thickness

Thinning Factor

Sediment Thickness

Greenhalgh & Kusznir, Geophys. Res. Lettr., 2007Chappell & Kusznir, Geophys. J. Int., 2008Alvey, Gaina, Kusznir & Torsvik, EPSL, 2008


Technique Validation

• Why is the thermal correction important?

• Gravity inversion without thermal correction predicts oceanic crustal thicknesses that are much too large


(Chappell & Kusznir 2008)

Crustal thickness

A

A’

Traditional Method ‐ no thermal correction OCTek Method ‐ using a thermal correction

Compare these predictions of crustal thickness

Without the correction the ocean floor and mid-ocean ridge are predicted to be far too thick and this effect also propagates into the rifted continental margins

Why is the thermal correction important?Technique Validation


Overview

• Petroleum Systems modelling, for which we produce maps of (i) beta/thinning factor & (ii) residual-continental-crustal-basement, across rifted margins and their ocean-continent transitions, plus (iii) a software tool to convert maps of beta/thinning factor into maps of top basement heat flow

We believe that the output from OCTek will be of particular assistance to:

• New Ventures exploration strategy in deepwater areas, helping to:

(i) determine location of the ocean-continent-transition

(ii) discriminate crustal type prior to any specific data acquisition

OverviewOCTek uses public domain data and published proven technology, which has also delivered confidential results on a proprietary basis working in the following geographic areas:

A study applying the OCTek gravity inversion methodology to the conjugate South Australia – Antarctic margins has been made available for free public download by Geoscience Australia Link to GA study

• South America

• West Africa

• Gulf of Mexico

• Arctic Ocean

• Asia-Pacific

• Indian Ocean

• Australia

• The Mediterranean

https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&catno=68655

• South America, inc. all of offshore Brazil

• West Africa, South Africa north to Morocco

• Atlantic southern Europe, Iberia and Biscay

• The eastern American/Canadian seaboard

The OCTek-Atlantic study investigated the conjugate margins of the Atlantic between 65oS and 60oN, an area which includes the South, Equatorial and Central Atlantic. The results will therefore be of interest to those exploring or evaluating the offshore basins of:

OCTek-Atlantic

• Papua New Guinea and Northern Australia

• The Indonesian, Malaysian, Philippine archipelago

• Gulf of Thailand, Andaman Sea, offshore Vietnam

• South China Sea and East China Sea

• Sea of Japan and Sea of Okhotsk

The OCTek-Asia/Pacific study investigated the complex rifted margins and associated extensional basins of the Asia-Pacific region between 20oS and 60oN, an area which includes the Pacific-rimming basins of SE Asia, East Asia and NE Asia. The results will therefore be of interest to those exploring or evaluating the offshore basins of:

OCTek-Asia/Pacific

• The east and west coasts of India, inc. the Bay of Bengal and Arabian Sea

• East Africa north to the Gulf of Aden

• Madagascar and the Mozambique Channel

• The Seychelles/Mascarene microcontinent

The OCTek-Indian Ocean project investigated the margins, rift basins and micro-continents of the Indian Ocean from its northern margin south to 35oS. The results will therefore be of interest to those exploring or evaluating the offshore basins of:

OCTek-Indian Ocean

• Arctic Canada & Alaska, incl. Beaufort & Chukchi Seas

• Arctic Russia, incl. East Siberia, Laptev, Kara & Barents Seas

• Arctic Norway & Greenland, incl. the Spitsbergen area

• Norwegian & East Greenland Atlantic margins, incl. Jan Mayen

• West Greenland, incl. Baffin Bay & Labrador Sea

• Western UK/Ireland Atlantic margin

The OCTek-Arctic/North Atlantic study has investigated the rifted margins and basins of the Arctic and North Atlantic, south to 50oN, where the study joins with OCTek-Atlantic . The results will therefore be of interest to those exploring or evaluating the offshore basins of:

OCTek-Arctic/North Atlantic

The primary output from all OCTek studies is a suite of digital grids for the full project area, plus a supporting digital report and atlas of maps, showing:

OCTek results

1. Depth to Moho

2. Total crustal thickness, including volcanic addition

3. Residual continental-basement crustal thickness, excluding volcanic addition

4. Crust and lithosphere thinning factor and beta factor

5. The residual thermal gravity anomaly at the present-day

The results grids in all OCTek reports:

• Are tuned to local breakup/rift age along the margins and within the basins of the study area

• Are tuned to local crustal reference thickness

- Typically in the range 35 - 45km

• Explore a range of plausible scenarios for the amount of volcanic addition during breakup:

- No volcanic addition (magma poor margin)

- 7km volcanic addition (normal margin)

- 10km volcanic addition (volcanic margin)

OCTek results

The purchase of any OCTek report allows the purchasing

company/institution unrestricted use of the grids in any

form they choose. A single report may be distributed around

multiple locations within the company. The grids are

supported by a digital report which documents the

techniques used and all of the maps produced.

OCTek results

Studies and reports currently available:

• OCTek Atlantic

• OCTek Arctic/North Atlantic

• OCTek Asia-Pacific

• OCTek Indian Ocean

OCTek heat-flow

Heat flow (mWm-2)

Each OCTek study also includes a simple software tool which will convert OCTek maps of thinning factor into maps of top basement heat-flow, constrained by your own input for local radiogenic heat productivity within the crust

As well as presenting the grids in their present-day coordinate framework the Atlantic Ocean crustal thickness grids have been sequentially restored, using recently-published stage-poles, from the present-day back to their palaeogeographic coordinates at the time of break-up. The restorations are included in the Atlantic report

OCTek-AtlanticPlate reconstructions

As well as presenting the grids in their present-day coordinate framework the Indian Ocean crustal thickness grids have been sequentially restored from the present-day back to their palaeogeographic coordinates at the time of break-up. This has shed new light on the complex breakup of the East Africa – Madagascar –Seychelles – West India margins. The restorations also extend south to include the Antarctic margin and are included in the Indian Ocean report

OCTek-Indian OceanPlate reconstructions

OCTek-Arctic/North Atlantic Plate reconstructionsAs well as presenting the grids in their present-day coordinate framework the Arctic/North Atlantic crustal thickness grids havebeen sequentially restored, using recently-published stage-poles, from the present-day back to their palaeogeographic coordinates at the time of break-up. The restorations are included in the Arctic/North Atlantic report

OCTek contact

For further information on OCTek please contact:

Dr Alan Roberts

Badley Geoscience Ltd

North Beck House

North Beck Lane

Hundleby, Spilsby

Lincolnshire, PE23 4NB

United Kingdom

[email protected]

+44 (0)1790 753472

www.badleys.co.uk

www.badleys.co.uk/products/octek.htmBADLEY GEOSCIENCE LIMITED

mailto:[email protected]

http://www.badleys.co.uk/


dr andy alvey – badley geoscience prof. nick kusznir ... · the octek team: dr andy alvey –...

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