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Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 1 January 2009 UK Offshore Licence P011 (Block 29/20a) 1 st Licensing Round (Traditional Licence) Relinquishment Report Licensee Maersk Oil North Sea UK Limited (100%) January 2009 Synopsis Block 29/20a was previously owned, and recently relinquished, by Maersk Oil North Sea UK Limited which held an undivided 100% interest (Figure 1). By Deed of Assignment dated 22 nd January 2004 Murphy Petroleum Limited assigned and transferred to Kerr-McGee North Sea (U.K.) Limited an undivided 50% participating interest in Licence P.011, Block 29/20a. Following the unsuccessful results of well 29/15-3 (drilled in August 2005) to target the Fyvvie Prospect, an Upper Jurassic Fulmar target that straddled the 29/15 and 29/20a block boundary, by Deed of Assignment dated 11 th August 2006, Murphy Petroleum Limited assigned and transferred to Maersk Oil North Sea UK Limited (previously named Kerr-McGee North Sea (U.K.) Limited) its remaining undivided 50% participating interest in Licence P.011, Block 29/20a and Maersk Oil North Sea UK Limited held an undivided 100% interest in Block 29/20a. Technical work has continued on a second opportunity identified by 29/20-1 well (drilled in October 1973). Attempts to farm out the Zechstein and Rotliegendes lead have been unsuccessful. The licence is at the end of if its term, being a 1 st round license requiring established production by September 2010 for retention. Given the discontinued exploration programme and the short remaining licence period the Block was relinquished in September 2008 at the request of the DECC. All work commitments on Block 29/20a have been fulfilled. Data and Work Programme No formal data or work programme was required for the block.

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Page 1: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 1 January 2009

UK Offshore Licence P011 (Block 29/20a)

1st Licensing Round (Traditional Licence) Relinquishment Report

Licensee Maersk Oil North Sea UK Limited (100%)

January 2009 Synopsis Block 29/20a was previously owned, and recently relinquished, by Maersk Oil North Sea UK Limited which held an undivided 100% interest (Figure 1). By Deed of Assignment dated 22nd January 2004 Murphy Petroleum Limited assigned and transferred to Kerr-McGee North Sea (U.K.) Limited an undivided 50% participating interest in Licence P.011, Block 29/20a. Following the unsuccessful results of well 29/15-3 (drilled in August 2005) to target the Fyvvie Prospect, an Upper Jurassic Fulmar target that straddled the 29/15 and 29/20a block boundary, by Deed of Assignment dated 11th August 2006, Murphy Petroleum Limited assigned and transferred to Maersk Oil North Sea UK Limited (previously named Kerr-McGee North Sea (U.K.) Limited) its remaining undivided 50% participating interest in Licence P.011, Block 29/20a and Maersk Oil North Sea UK Limited held an undivided 100% interest in Block 29/20a. Technical work has continued on a second opportunity identified by 29/20-1 well (drilled in October 1973). Attempts to farm out the Zechstein and Rotliegendes lead have been unsuccessful. The licence is at the end of if its term, being a 1st round license requiring established production by September 2010 for retention. Given the discontinued exploration programme and the short remaining licence period the Block was relinquished in September 2008 at the request of the DECC. All work commitments on Block 29/20a have been fulfilled. Data and Work Programme No formal data or work programme was required for the block.

Page 2: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 2 January 2009

Figure 1: Location of Block 29/20a

Page 3: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009

Prospectivity Review Tectono-Stratigraphic Setting Block 29/20a lies on the south-easterly edge of the Western Platform, adjacent to the West Central Graben. The Auk Zechstein dolomite and Rotliegendes sandstone field lies approximately 5 km east of the block. Exploration Potential The most likely exploration potential remains in the Zechstein and Rotliegendes. Operators View of Remaining Prospectivity Zechstein and Rotliegendes Up-dip of 29/20-1 a Zechstein and Rotliegendes lead has been identified. The lead is a structural and possible stratigraphic trap formed by lateral/vertical change in facies from non-net anhydrite/limestone to fractured dolomite, and a structural trap at Rotliegendes level. The lead extends into 29/20b, however mapping is limited by available seismic data in the neighbouring block. The seismic datasets available in the block are shown on Figure 2. Well 29/20-1 drilled in 1973, penetrates over 600ft of Zechstein anhydrites and carbonates partly hydrocarbon bearing. The net reservoir is a relatively clean, dolomitic interval in the middle of the Zechstein. Re-evaluation of the petrophysics by Maersk Oil on 29/20-1 found 38.5ft net pay in the Zechstein Z1 dolomites with average pay porosities of 18% and average water saturation of 35%. The reservoir quality and hydrocarbon saturations are comparable to the nearby producing Auk field. It is likely the 29/20a area depositional environment for the dolomites with later alterations resembles the conditions prevailing at the Auk ridge. As a result, the dolomites will have developed similar vuggy and fracture secondary porosity. Top and lateral seal is provided by a thick Zechstein anhydrite development. The 29/20-1 well TD’d in wet Rotliegendes, but as shown by the cross-section in Figure 3, there could be hydrocarbons present updip to the south of the well (Figure 5). The 29/20-2 well did not reach the Permian (TD’d in the Triassic). The Zechstein lead has an estimated STOIIP range of 25 to 45 mmbbls. A forced closure to the SW at 8,340ft TVDSS and the Sand SW at the edge of the seismic data delimits the areal extent of the prospect. The Rotliegendes lead has an estimated STOIIP of 54 mmbbls, with an assumed trap closure near 8,525ft TVDSS. Analogue data: The Auk Field, immediately to the east in block 30/16, produces hydrocarbons from fractured Zechstein dolomite and Rotliegendes sands. In Auk, the Zechstein is on average 25-30 ft, and is of fairly uniform thickness (except where eroded). Average Petrophysical properties of the Zechstein are: 2-26% matrix porosity, 53mD average permeability and additional fracture/vuggy porosity (enhanced by sub-aerial weathering).

Page 4: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 4 January 2009

Figure 2: Available Seismic Datasets

Page 5: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 5 January 2009

Figure 3: Petrophysical Evaluation of well 29/20-1 in the Zechstein

Page 6: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 6 January 2009

Figure 4: Top diagram: Arbitary line through 29/20-1 and 29/20b-2 wells. Bottom Diagrams: Top Zechstein Depth Map and thickness map based on CGG Veritas Quad 30 3D Seismic Survey

Page 7: Maersk Oil North Sea UK Limited · Maersk Oil North Sea UK Limited Maersk Oil UK Limited – 29/20a Relinquishment Report 3 January 2009 Prospectivity Review Tectono-Stratigraphic

Maersk Oil North Sea UK Limited

Maersk Oil UK Limited – 29/20a Relinquishment Report 7 January 2009

Figure 5: Top Rotliegendes Depth Map – section line relates to cross-section shown in Figure 2 All other stratigraphic levels No hydrocarbon potential recognised. Geological Risk There is significant exploration risk associated at both stratigraphic levels restricting the prospect potential; the key element being reservoir presence where more accurate prediction requires the understanding of facies distribution and control in the Zechstein. Additional risk is hydrocarbon migration. The source rock in the area is the Kimmeridge Clay or the Carboniferous Scremston Coal formation (gas prone), but both require long distance migration and through tortuous pathways, in the case of the Scremston coal. Summary Based on the evaluation to date the lead identified in 29/20a is not ready for drilling and further work is needed to achieve prospect status. In conclusion, the remaining prospectivity of the block is interesting; however there is the need to acquire further seismic data on the western side of the lead to delimit the structure.