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Noble Energy (Europe) Limited Blocks 15/14 and 15/15, Licence P1172, UKCS - Relinquishment Report

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Relinquishment Report

Blocks 15/14 and 15/15 (Licence P1172)

UK North Sea

February 2008


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Document Title:

Relinquishment Report, Blocks 15/14 and 15/15 (Licence P1172), UK North Sea

Revision History:

Revision Date Description Originator

1.0 25/02/08 First Draft Owen Stephens

2.0 25/02/08 Final Draft Owen Stephens

Distribution List:

Copy No. Recipient Location

1 Chris Newton, Exploration Manager NE Europe, Sevenoaks

2 Department of Trade & Industry London

3 P1172 file NE Europe, Sevenoaks


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1. HEADER

Licence Number P1172

Licence Round 22nd Offshore Licensing Round

Licence Type Traditional

Block Numbers 15/14, 15/15

Equity Noble Energy (Europe) Limited, 100%

Work Programme Summary

Drill-or-drop Work Programme Part 1: Firm commitment Within one year of the beginning of the Initial Term, the Licensee shall obtain 270km of 2D seismic data. Part 2: The Licensee shall drill one well to a depth of 2000m or 50m into the Maureen Formation, whichever is the shallower.

2. SYNOPSIS

This report follows complete relinquishment of blocks 15/14 and 15/15 at the end of the licence initial term.

3. EXPLORATION ACTIVITIES

The firm licence commitment to obtain 270km of 2D seismic data was fulfilled by licensing 2D spec lines from the regional NSR survey shot by TGS. 450km of this data had previously been shot, while the shooting of a further 650km of data was underwritten by Noble.

These newly purchased data were combined with older 2D data, obtained before the licence application, and interpreted to refine the predicted volumes. Some of the seismic lines included offset data, and these were used to try to predict the presence of hydrocarbons from rock physics analysis and thereby reduce geological risk.

4. PROSPECTIVITY ANALYSIS

Reservoir

Three ages of reservoir targets are recognised in areas close to the Fladen Ground Spur, where blocks 15/14 and 15/15 are located. These are the Devonian and lower Carboniferous, Jurassic, and Palaeocene and Eocene. No valid undrilled structures have been identified at Palaeozoic or Mesozoic levels, so study has concentrated on deep-water Palaeocene and Eocene sandstones of the Montrose Group.


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Fig. 2 shows a well correlation across the licence. Sand is present in the Maureen Formation and Andrew and Balmoral Sandstone Members of the Lista Formation, with the highest sands pinching out to the east such that only the oldest Maureen sand is present in well 15/15- 1.

In this area, Palaeocene deep-water sandstones form good quality, laterally-continuous reservoirs, with average porosities generally between 25% and 30%. Net-to-gross is also generally high, in the 60% to 90% range, though the youngest sands deposited during abandonment of the depositional axis are often more shaly at the very top.

Sandstones within the Eocene Balder Formation are present in block 15/14, but no structural closure is present at this level.

Source and Migration

The Jurassic Kimmeridge Clay Formation is the source rock for all fields in the surrounding area. While the Jurassic is not sufficiently deeply buried for hydrocarbon generation on the Fladen Ground Spur, it is in the southern Viking Graben to the east, and in the Witch Ground Graben to the southwest. Of the two, the Viking Graben is considered to be the most likely source for structures on the licence, with oil migrating up the graben-bounding faults, then along the regional dip to the west-northwest. However, the shows in the Eocene in well 15/14b- 3 do suggest that oil may have migrated up major faults directly into the Eocene, bypassing the Palaeocene structures in the process.

Containment

More than 200ft of continuous Lista Formation mudstones are predicted to overlie the potential target sanstones, reaching over 1000ft in parts of Block 15/14. The only exception to this is in the far west of Block 15/14, away from the recognised prospects, at the pinchout edge of deltaic sands of the Dornoch Formation of latest Palaeocene age.

Trap

Two structures are mapped on the licence, both four-way-dip closures at Top Balmoral level. One of this lies in the east of Block 15/14 and the other in the northeast of Block 15/15.

Prospect Volumetrics and Risking

The 15/14 lead mapped as containing P90/P50/P10 resources of 2.3/8.5/31.1 mmbo, including oil and dissolved gas. The 15/15 lead is mapped at 1.71/5.21/30.1 mmbo.

Unfortunately, the seismic offset stacks provided no evidence for the presence of hydrocarbons within the mapped prospects, even though rock physics analysis of the surrounding wells implies that hydrocarbons should be identifiable as either class IIp or class III AVO anomalies. One possible explanation for this is that any oil sourced from the South Viking Graben migrated up the bounding faults directly into the Eocene and then updip to the west. As such, the leads are considered to be very high risk and therefore uneconomic to drill.


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5. RESERVES SUMMARY

No remaining potential is seen on Blocks 15/14 and 15/15.

6. MAPS AND FIGURES

Figure 1 Top Montrose Group Sands Depth Map (ft)

Figure 2 Well Correlation

Figure 3 Seismic line across 15/15 prospect

7. CLEARANCE

Seismic line SUK 92-109 shown in figure 3 is public data.


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Figure 1. Top Montrose Group Sands Depth Map (ft)

15/1

5 le

ad

1° E

58°

40’ N

0° 3

6’ E

15/1

4 le

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Figure 2 Well Correlation


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Figure 3 Seismic line across 15/15 prospect

W

E

Top

Bal

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Int

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N

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Bal

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Top

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