RELINQUISHMENT REPORT FOR LICENCE P.1442 BLOCK 48/9d

Transcription

1 RELINQUISHMENT REPORT FOR LICENCE P.1442 BLOCK 48/9d Licence: P.1442 Block: 48/9d 24 th Round Traditional Licence Operator: Ithaca Energy UK(Ltd) 44.85% Partner: Dyas % EWE 40% Work Programme Summary: Acquire 80km 2 of 3D seismic data fulfilled. Drill or drop decision required by 2 nd anniversary (1 st April 2009). SYNOPSIS The licence was acquired on 1 st April 2007 by Ithaca Energy (UK) Ltd (Operator) and EWE Oil and Gas Ltd as a Traditional licence in the 24th round of licensing. Dyas joined the partnership in Block 48/9d lies on the north-west margin of the Leman Sandstone gas fairway. Analogous producing fields lie km to the NW (North & South Ravenspurn, Johnston), c.5-10 km to the South (Mimas)and Southeast (Saturn) and c.10km to the west (Hoton). In addition to the above, several discoveries remain undeveloped nearby e.g. Seven Seas, Babbage and Cobra. Block 48/9d is bounded to the south by the NE-SW trending Sole Pit Basin and the NE-SW trending Silverpit Basin to the north. Permian (Lower Leman Sandstone Formation) and Carboniferous (Westphalian and Namurian) sandstones form the main reservoir units in the bounding basins. The main Permian sandstone unit, the Leman Sandstone, rests unconformably on older Carboniferous deposits in this area. The Upper Permian Leman is the target reservoir and although a very thick section is expected to be present there are risks associated with the reservoir properties in this area. A robust prospect has been mapped in the block but the depth conversion is difficult because of an adjacent salt wall and there is therefore a significant risk on the GRV of the prospect. In the event the critical factor against further commitments in this licence was the absence of any viable economic opportunities in the block due to the small size (P50 in place reserves, 38bcf ), the risk (0.3) and the absence of easy access to infrastructure for Ithaca of the prospect, the partnership has decided to relinquish the licence Page 1

2 Fig 1. Location Map of Block 48/9d Licence P.1442 EXPLORATION ACTIVITIES A complete 2D and 3D seismic interpretation has been undertaken using available data and maps have been generated on the Base Tertiary, Top Triassic, Top Bunter sandstone, Top Zechstein and Top Rotliegend events. Complex salt structures are recognized locally which severely degrade the seismic expression of the sub-salt geology and imparts strong velocity distortions to the sub-salt structural geometry. This effect has severely hindered previous exploration activity in the area and increases the risk on prospect evaluation. No wells have been drilled on 48/9d but three wells have been drilled on the nearby Mimas Field(48/9-1, 48/9a-2 and 48/9a-3) Page 2

3 PROSPECTIVITY ANALYSIS IN BLOCK 48/9d In summary: The principle reservoir target is the Leman Sandstone, reservoir quality is the critical issue as many wells in this area have poor poroperm although there have also been successful developments in these poor reservoirs. The source of the dry gas encountered in nearby fields is the Carboniferous Westphalian coals. This source is no longer generating gas and therefore timing of migration versus structure formation is a critical factor. The regional seal is the Zechstein evaporates. The Silver Pit Shales can act locally as a top seal. Platten dolomites are present and can act as a thief zone if juxtaposed against the Rotliegend section. The main trap types are structural with a dominant NW-SE orientation but are expected to be complex because of cross-cutting sealing faults. Difficulties of mapping and the depth conversions below the Zechstein are critical issues affecting confidence in the structures. Reserves Summary A structural pop up with three way dip closure against a NW-SE aligned fault has been identified and mapped at the Top Rotliegend level in block 48/9d. This is a robust three way dip closure with considerable amplitude (c.140m) although because of the presence of widely varying salt thicknesses (300m to 1500m) the true structure of the pre-zechstein is difficult to determine and constitutes a major risk. A similar level of risk needs to be factored in for the Leman reservoir because of the poor reservoir quality that has been experienced in many of the adjacent wells although this has not stopped development proceeding. The small volumes and associated risks for this prospect have led to the partnership concluding that a well cannot be justified. Prospect 48/9d Styx Type: An elongate 3-way dip closure with a faulted eastern margin. Risks: Structure: The structure can be readily mapped on the 3D but the amplitude of the structure and therefore volumes are very sensitive to time-depth conversion, amplitude however appears high. (0.7) Page 3

4 Timing/Migration: The structure existed at the time of migration but may have continued to develop after migration and may not therefore be filled to spill. (0.8) Seal: There is a trap integrity risk due to the presence of Platten dolomite which can act as a thief zone when juxtaposed against the Rotliegend section.(0.8) Reservoir: Very likely to be present and at least 100m thick, reservoir quality is a risk in this area. (0.7) Overall Risk = 0.3 Gas in Place: P90 22 bcf P50 38 bcf P10 70 bcf Fault linkage following 3D interpretation Ithaca Depth Map (Feet) Fig 2. Top Rotliegend map on Prospect Styx in Block 48/9d Page 4

5 Fig 3. Seismic section across the Styx Prospect in Block 48/9d Page 5