Potential future exploration opportunities, UK Rockhall Basin

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Potential future exploration opportunities, UK Rockall Basin

154/1-1NW SE

2.0

1.0

3.0

4.02 km

TWT(s)

1. Introduction

Since 1999, the Department of Energy and Climate Change (DECC) (formerly the Department of Trade and Industry) has conducted Strategic Environmental Assessments (SEAs) prior to offshore licensing rounds.

SEA7 lies within the Atlantic Margin area, and its assessment was completed during 2007.

SEA7 incorporates Rockall Basin Quadrants 127-132, 138-142, 147-154, 157-165, 168-171 and 173-174, as well as parts of the adjacent Outer Hebrides Platform and Rockall High, plus parts of the Hatton Basin and Hatton High. However, only the area to the east of 13°W is currently available for licensing.

The remaining unlicensed acreage in SEAs 1 to 6, and SEA8 will also be available for licensing in the next offshore licensing round.

Fig. 1 Areas potentially open for licensing in the next offshore licensing round. Actual blocks on offer (including terms) and the timing of any Round will be announced on the DECC website .www.og.decc.gov.uk

Proven source rocks

Proven hydrocarbon systems

Proven traps

Proven reservoirs in post-rift and pre-rift plays:

- Benbecula Paleocene

Gas discovery

- Dooish (Irish Sector) Permo-Triassic and Middle

Jurassic

G a s c o n d e n s a t e

Fig. 2 Licensed areas and water depths acrossRockall Basin

2

3

5

41

713°W

7

6

8

ATLANTIC MARGIN

Extension

22

IRISHSEA

NORTHSEA

Completed SEAs

SEA7: not available for licensing at present

SEA7: available for licensing

SCOTLAND

ENGLAND

WA

LE

S

The Rockall Basin has:

Continent-O

cean Boundary

5°W

5°W10°W15°W20°W25°W

0°E

0°E

10°W

55°N

60°N

Roc

kall

Bas

in

Hatton H

igh

Fig. 7

Rockal

l H

igh

Hatton B

asin

Ireland

Scotland

England

Shetland

FaroeIslands

Dooish discovery

Heb

ridea

n

Platfo

rm

Steeply dippingpre-Tertiary reflectorsof Keser Neish (1993)

Synrift dippingreflectors of Boldreeland Andersen (1994)

Synrift prospectidentified by Smith

et al. (1999)

Faro

e-She

tland

Bas

in

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High Igneous centre

Eastern limit ofbasalt in Faroe-Shetland Basin

Southern limit ofthick basalt in Rockall Basin

0~1000 m

27th Round potentialaward (November 2012)

27th Round application block

Licensed blocks(November 2012)

Oil field/discovery

Gas field/discovery

1000~2000 m

Water depth

2000~3000 m

250 km

Benbecula discovery

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Continent-O

cean Boundary

Roc

kall

Bas

in

Hatton H

igh

Fig. 7

Rockal

l H

igh

Hatton B

asin

Ireland

Scotland

England

Shetland

SlyneBasin

Corrib gasdiscovery

Erris B

asin

Wyville-Thom

son

Transfer

Judd

Transfer

Faroe-ShetlandEscarpment

Heb

ridea

n

Platfo

rm

Steeply dippingpre-Tertiary reflectorsof Keser Neish (1993)

Synrift dippingreflectors of Boldreeland Andersen (1994)

Synrift prospectidentified by Smith

et al. (1999)

Iceland-Faroe

Ridge

Faro

e-She

tland

Bas

in

North-East

Rockall Basin

High Igneous centre

Eastern limit ofbasalt in Faroe-Shetland Basin

Southern limit ofthick basalt in Rockall Basin

0~1000 m

27th Round extantaward (November 2013)

27th Round application block

Licensed blocks(November 2013)

Oil field/discovery

Gas field/discovery

1000~2000 m

Water depth

2000~3000 m

250 km

Dooish discovery

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154/1-1NW SE

2.0

1.0

3.0

4.02 km

TWT(s)

UK

UK

Faroes

Ireland

14°W 13°W 12°W 11°W 10°W 9°W 8°W 7°W

57°N

58°N

59°N

60°N

0 30 60 90 120 150

Kilometres

150 154151 153152 155

144

134 135

140 141 143142

130131

133132

139

128 129127

138

148 149

158 159 160 161

157

147

137

169

164163162 165

174175

SulaSgeir

164/7-1

164/25-2

164/25-1Z

154/3-1

154/1-2

154/1-1

164/27-1

164/28-1A

153/5-1

163/6-1A

Anton Dohrn

Rockall

132/15- 1

Fig. 7

Fig. 6

Fig. 5

132/6- 1

St.Kilda

Hebrides Terrace

Modified after BGS 2007 & 2002

Fig. 3 Principal structural elements, Rockall Basin area

OuterHebridesPlatform

BarraBasin

StantonBasin

Sea of theHebrides -

Little MinchBasin

North-EastRockallBasin

WestFlannanBasin

RonanBasin

East RockallHigh Basin

WestLewisBasin

WestLewisHigh

Darwin-GeikieHigh

Wyville-ThomsonRidge

FlannanBasin

Rosemary Bank

Sigmundur

Lousy High

?

Darwin

Drekaeya

Faroe Bank Channel Knoll

Geikie

RockallHigh

NorthRockall Basin

SouthRockall Basin

HattonHigh

Ymir Ridge

WestGeorgeBligh

EastGeorgeBligh

2. Structural Elements

The Rockall Basin is a N-S to NNE-SSW trending graben lying between the Rockall High in the west, and the Outer Hebrides Platform in the east. The North-East Rockall Basin is separated from the Faroe-Shetland Basin to the north-east by the Wyville-Thomson Ridge. Late Cretaceous to Early Eocene igneous intrusions are present within the basin and on the bounding highs. Associated lavas and tuffs cover much of the basin, and older strata in large parts of the basin are obscured on seismic data by thick extrusive rocks. The oldest sedimentary rocks penetrated within the UK sector of the Rockall Basin are Early Cretaceous (South Rockall Basin well 132/15-1); however, Jurassic rocks are inferred from seismic interpretation to be present across at least the eastern part of the Rockall Basin (Spencer et al. 1999).

Tertiary and Mesozoic/Palaeozoic on basement

Fault

Lava escarpment

Cretaceous and older Mesozoic/Palaeozoic on basement

Mapped limit of Paleogenelavas within Rockall Basin

Possible Cretaceous and older basin beneath lavas

Limit of SEA7

Jurassic and older Mesozoic/Palaeozoic on basement

Permo-Triassic on basement

Platform, including Palaeozoic basins, Paleogene lavas

Buried high (inferred basement high)

Igneous centre

High (top Paleogene lavas), little or no Tertiary cover

High, origin unknown

Fig. 8



154/1-1NW SE

2.0

1.0

3.0

4.02 km

TWT(s)

Seabed

Seabed

Seabed

Seabed

Basalt/tuff

Dacite

Dolerite

Basalt breccia

Sandstone - volcanigenic

Sandstone/conglomerate

Post-Eocene

Eocene

Paleocene

Cretaceous

Age unknown

Permo-Triassic

Basement

132/6-1

South RockallBasin

North-EastRockall Basin

North RockallBasin

West LewisHigh

West LewisBasin

132/15-1 164/28-1A153/5-1Benbecula

154/1-1 164/25-1Z164/25-2

0

2000 ft

Vertical scale

163/6-1A 154/3-1164/7-1

Fig. 4 Distribution of sandstones in released UK exploration wells, Rockall Basin area. See Fig. 3

3. Rockall Basin area wells

Seven released hydrocarbon exploration wells have been drilled in the UK Rockall Basin, with two in the South Rockall Basin, four in the North-East Rockall Basin, and one in the North Rockall Basin. Two further wells were drilled on the adjacent West Lewis High and one in the West Lewis Basin.

Two of these wells found hydrocarbons. The Paleocene post-rift play was proven by the discovery of gas in the Vaila Formation at well 154/1-1 (Benbecula discovery), and oil shows were found within the Vaila Formation in well 164/28-1A. However, the remaining five released Rockall Basin wells were dry holes.

In the Irish sector of the South Rockall Basin, the Dooish gas condensate discovery (see Fig. 2) is reported to comprise Permian reservoir sandstones (Shannon et al. 2005). Thick Permo-Triassic sandstones were proven in the West Lewis Basin, and equivalent beds are likely to be present locally in the Rockall Basin, at least along its eastern margin.

Quartzose sandstones were penetrated in the Paleocene sections of 5 of the UK Rockall area wells (Fig. 4). Volcanigenic sandstones with poorer reservoir potential make up the clastic component of the Paleocene at well 132/15-1. Wells 163/6-1A and 164/7-1 drilled through very thick Palaeogene volcanic sections, although this is probably due to their proximity to the Darwin igneous centre (Fig. 3).

Eocene sandstones were penetrated in 7 of the 10 Rockall area wells.

Seabed

Seabed

Seabed

Seabed Sea

bed

Seabed



154/1-1NW SE

2.0

1.0

3.0

4.02 km

TWT(s)

1

2

3

5

4

TWT(s)

WESTLEWISHIGH

Fig. 5 Seismic section and geoseismic interpretation across the North-EastRockall Basin. See Fig. 3 for location of section.

NORTH-EAST ROCKALL BASIN

10 kmBasement (Precambrian)

Jurassic to Cretaceous(base conjectural)

Paleocene to early EoceneEocene

Oligocene

Miocene to Recent

Intrusives

Top Balder Fm

Post-rift plays

Syn-rift and latepre-rift plays

Pre-rift plays

1

2

3

5

4

TWT(s)

SENW

WESTLEWISHIGH

NORTH-EAST ROCKALL BASIN

10 km MC3D seismic data courtesy of PGS

4. North-East Rockall Basin

A range of pre-, syn- and post-rift plays are envisaged in the North-East Rockall Basin. Five hydrocarbon exploration wells have been drilled on the eastern margin of the basin (Fig. 3). The Paleocene post-rift play was proven by the discovery of gas in the Vaila Formation at well 154/1-1 (Benbecula discovery), and the occurrence of oil shows within the Vaila Formation in well 164/28-1A. However, wells 153/5-1

and 164/27-1 were dry holes. The remaining well has not been released into the public domain.

Eocene mass-flow complex play:

slope channel, proximal fan

channel and fan lobe stratigraphic

traps cf. Tobermory gas discovery,

Faroe-Shetland Basin

Paleocene mass-flow

complex play: slope channel, proximal fan


traps e.g. Benbecula gas discovery, NE Rockall Basin

Late Jurassic-Early Cretaceous basinal sand play:

conjectural

Palaeozoic-basement play:

Devono-Carboniferous

and/or fractured basement fault trap

cf. Clair Field, Faroe-Shetland

Basin

Permo-Triassic play:

e.g. Dooish gas condensate

discovery, Irish

1

2

3

4

4

1

2

3

4



Fig. 6 The Benbecula gas discovery was made in Upper Palaeocene-aged Vaila-equivalent sandstones, slightly down dip from the crest of a foot-wall syncline exhibiting four-way dip closure. The overlaying Kettla Member-equivalent acts as the reservoir seal (Seismic data courtesy of PGS).

5. Hebridean Margin Plays(North east)

Seismic data across the North east-ern Rockall Basin reveals the po-tential for various styles of play along the basin margins. Four wells have been drilled to data, p r o v i n g t h e p r e s e n c e o f Palaeocene-and Cretaceous-aged successions within the ba-sin. Well 154/1-1, which made the Benbecula gas discovery proved the existence of a working petro-leum system, with the subsequent well 165/28-1A encountering hy-drocarbon stained sandstones w i th in the Pa leocene- and Eocene-aged succession. As of yet, the source rock for these hy-drocarbons has not been encoun-tered in any wells within the basin. However, the presence of a work-ing petroleum system suggests that Jurassic- or Carboniferous-aged source rocks occur at depth. Although intrusive igneous activity is pervasive within the basin, sills

Post-rift plays


Pre-rift plays


slope channel, proximal fan channel and fan lobe stratigraphic traps cf.

Tobermory oil discovery, Faroe-Shetland Basin

Paleocene mass-flow complex play:

slope channel, proximal fan channel and fan lobe stratigraphic traps cf.

Benbecula gas discovery, NE

Turonian sandstone play: basin-floor fan traps in

hanging wall of basin-margin faults cf. well 206/3-1, Faroe-

Late Jurassic-Early Cretaceous basinal sand

play: conjectural


Devono-Carboniferous and/or fractured basement fault trap cf. Clair Field, Faroe-Shetland

Basin

Permo-Triassic play: e.g. Dooish gas condensate discovery, Irish Rockall Basin

1

2

3

4

5

5

See Upper Cretaceous sandstoneplay, Atlantic Margin (click here)

are typically confined to depths be-tween 3000 – 10,000 ft (1 – 3 km), potentially sparing any deeper source rocks from undue heating.

154/1-1NW SE

2.0

1.0

3.0

4.02 km

TWT(s)

W E

Middle/Upper Eocene

Lower Eocene

Middle Cretaceous (Turonian to Cenomanian) Potential stratigraphic trap

Lower Cretaceous

Jurassic

Triassic

Precambrian basement

Sills (Palaeogene intrusives)

Paleocene

Upper Cretaceous (Santonian to Maastrichtian)

Post-rift

Syn-rift

Pre-rift

2.5

4.0

3.5

4.5

5.0

5.5

TWT(s)

2 km

Potential deep Jurassic trap

Potential Cretaceousstratigraphic trap

1

3

4 4

5

5Pre-Cretaceous basin

2

Basementridge

Fig.7 Hebridean Margin Plays

Top Fan

Top Fan

Top EoceneUnconformity

Top VailaSandstone

Top VailaSandstone

Sill



6. Post-rift Plays

Paleocene plays

Eocene deepwater channel/fan complexes are clearly imaged on seismic data across the Rockall Basin. These bear a close similarity to the Eocene channel/fan com-plexes of the Faroe-Shteland Basin, as proven by several wells, and hydrocarbon-bearing at Tobermory well **-1. This play is documented in the poster ********

Eocene channel/fan com-plexes

Eocene deepwater channel/fan complexes are clearly imaged on seismic data across the Rockall Basin. These bear a close similarity to the Eocene channel/fan com-plexes of the Faroe-Shteland Basin, as proven by several wells, and hydrocarbon-bearing at Tobermory well **-1. This play is documented in the poster ********

Fig. 8 Seismic section and geoseismic interpretation across the western margin of the South Rockall Basin. See Fig. 3 for location of section.

Post-rift plays


Pre-rift plays

2

2

3

3

5

5

4

4

TWT(s)

TWT(s)

SENW

ROCKALLHIGH

SOUTH ROCKALL BASIN

SOUTH ROCKALL BASIN

10 km

6. Western margin of Rockall Basin

No hydrocarbon exploration wells have been drilled as yet along the western margin of the Rockall Basin, and there is limited seismic data available. However, a range of pre-, syn- and post-rift plays is envisaged on the western margin of the Rockall Basin, similar to those identified along its eastern margin.


slope channel, proximal fan


traps cf. Tobermory gas discovery,

Faroe-Shetland Basin

Paleocene mass-flow

complex play: slope channel, proximal fan


traps e.g. Benbecula gas discovery, NE Rockall Basin

Late Jurassic-Early Cretaceous basinal sand play:

conjectural


Devono-Carboniferous

and/or fractured basement fault trap

cf. Clair Field, Faroe-Shetland

Basin

Permo-Triassic play:

e.g. Dooish gas condensate

discovery, Irish Rockall Basin

1

2

3

4

4

10 km

Basement(Precambrian)

Late Eoceneto Recent

Top Balder Fm

Eocene(Prograding

wedge)Paleogenelavas

Cretaceous-?Jurassic or ?Permo-Triassic(base conjectural)

?

?

Cretaceous(? and Jurassic)

10 km

Paleoceneto early Eocene

Intrusives

SOUTH ROCKALL BASIN

1

2

3

3

4

4



8. Future Challenges and Summary

The Benbecula gas discovery and oil shows observed in 154/1-1 demonstrate the existence of a working hydrocarbon charge system in the North-East Rockall Basin. Additionally, the Dooish discovery in the Irish sector demonstrates the potential of a working hydrocarbon system within the south Rockall Basin of the UK sector.

Gravity and magnetic modelling of the Rockall Basin suggests that 4-6 km of sediment has accumulated across most of the Rockall Basin, with potentially more than 10 km of sediment at the centre of the North-East Rockall Basin.

From reconnaissance mapping, one Upper Cretaceous sandstone lead and three Eocene channel/fan complex leads have been recognised. Migration of hydrocarbons into the reservoir is likely to be the principal risk for the Eocene play due to the uncertainty of distribution of source rocks, and the localised presence of thick Paleogene volcanics.

Successful sub-basalt imaging is a key enabling technology for exploration of all Paleocene and sub-Paleocene Rockall Basin plays.

ReferencesBritish Geological Survey and Petroleum Affairs Division, Ireland. 2002. Central Rockall Basin, Sheet 56°-58°N, 08°-15°W, 1: 500,000 Series, Solid

Geology. British Geological Survey.

British Geological Survey. 2007. North Rockall Basin, Sheet 58°-60°20’N, 06°-13°W, 1: 500,000 Series, Bedrock Geology. British Geological Survey.

Grant, N, Bouma, A & McIntyre, A. 1999. The Turonian play in the Faroe-Shetland Basin. In: Fleet, AJ & Boldy, SAR (eds) Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference, 661-673. Geological Society, London.

Kimbell, G. S., Ritchie, J. D., Johnson, H. & Gatliff, R. W. 2005. Controls on the structure and evolution of the NE Atlantic margin revealed by regional 3D gravity modelling. In: Doré, A. G. & Vining, B. A.. (eds) Petroleum Geology: Northwest Europe and Global Perspectives - Proceedings of the 6th Conference, Geological Society, London, 933-945.

Shannon, PM, Faleide, JI, Smallwood, JR & Walker, IM. 2005. The Atlantic Margin from Norway to Ireland: geological review of a frontier continental

margin province. In; Doré, AG and Vining BA. (eds) Petroleum Geology: North-West Europe and Global Perspectives - Proceedings of the 6th Petroleum Geology Conference. Geological Society, London.

Spencer, AM, Birkeland, Ø, Knag, GØ & Fredsted, R. 1999. Petroleum systems of the Atlantic margin of northwest Europe. In; Fleet, AJ and Boldy, SAR (eds) Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference, 231-246. Geological Society, London.

The material presented on this panel is for information only. Whilst every effort has been made to ensure that the information provided is accurate, it does not constitute legal, technical or professional advice.

For more information contact:

Joy Gray ( ) [email protected] Nick Loizou ( ) [email protected]

7. Leads and dicoveries in the Rockall Basin

Examples of discoveries and undrilled leads in the Rockall Basin are shown in:

W e s t o f B r i t a i n opportunities

Click here for link

8°W10°W12°W14°W16°W

60°N

58°N

59°N

57°N

Sed

imen

t T

hic

kn

ess (

km

)0-0.5

0.5-1

1-2

2-3

3-4

4-6

6-8

8-10

10-18

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&##

&

###%

$

N.E.RockallBasin

NorthRockallBasin

SouthRockallBasin

OuterHebridesPlatform

RosemaryBank

FaroesUK

UKIreland

Fig. 8 Thicknesses of sediments accumulatedacross the Rockall Basins

(Kimbell et al., 2005)

0 80 200(km)

The Rockall Basins situated within the SEA7 area is a lightly explored, very challenging, mainly deep-water, frontier area with no existing infrastructure.

A range of hydrocarbon plays has been identified in the pre-, syn- and post-rift sections.

Documents

Potential future exploration opportunities, UK Rockhall Basin