RELINQUISHMENT REPORT Block 50/16 Southern North Sea UK · Relinquishment report block 50/16 3 Fig....
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Relinquishment report block 50/16 RELINQUISHMENT REPORT Block 50/16 Southern North Sea UK Dec 2007 Revision: 0 Date: 17-Jan-08
Transcript of RELINQUISHMENT REPORT Block 50/16 Southern North Sea UK · Relinquishment report block 50/16 3 Fig....
Relinquishment report block 50/16
RELINQUISHMENT REPORT
Block 50/16
Southern North Sea
UK
Dec 2007
Revision: 0
Date: 17-Jan-08
Relinquishment report block 50/16
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License Situation Block 50/16 was awarded to Shell (50%, operator) and its co-venturer Esso (50%) as part of the UK 21st offshore licensing round in Sept 2003. The initial 4 year license period expired end Sept 2007.
Geological setting
The 50/16 block is located in the southern part of the Cleaver Bank High area. The generalised stratigraphy is shown in Fig. 1.
The Upper Rotliegend Group consists dominantly of undifferentiated aeolian/fluvial coarse deposits of the Leman Sandstone Formation. Intercalation with the playa sediments of the Silverpit formation starts immediately north of the block.
Considerable movement of the Zechstein salt has taken place, creating salt ridges in some areas, and leaving behind only the Zechstein hard rock in other areas.
The Base Cretaceous Unconformity cuts deep into the Triassic Bacton Group over most of the area, with the Bunter Sandstone only preserved in places. Locally, pods of Haisborough Group sediments have been preserved. Based on seismic evidence no Haisborough Group sediments are present over the area.
Seismic Data The area is covered by the Cleaver Bank High 3D survey acquired in 1993. There are two seismic datasets available over block 50/16: A Post-Stack Time Migration (PosSTM) processed in 1993 and a Pre-Stack Depth Migration (PreSDM) processed in 2006. A North-South seismic section over the northern part of the block from the 2006 PreSDM is shown in Fig.2.
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Fig.1: Stratigraphic column in the area
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Fig. 2: SW/NE 3D Seismic section over the northern part of 50/16 block Well data Only one exploration well has been drilled in the 50/16 block. Well 50/16-1 was drilled in 1984 by BG and found the Rotliegend formation water-bearing within a high relief structural closure. The structure is most likely dry because of lateral seal failure along the bounding fault. Another reason for failure is lack of access to charge, as long distance migration is required from the north.
Prospectivity Prospectivity in the block is limited to the Rotliegend level. All prospects rely on long distance gas migration. Some low relief structural closures remain at Top Rotliegend in the northern part of the block. Due to the complex overburden these structures also suffer from a high uncertainty in gross rock volume and gas column height. Top and lateral seal are provided by Zechstein salt. A major risk is that of no recovery due to short column height. The low relief also adversely affects the recovery factor due to expected early water breakthrough. Reservoir modeling undertaken on the Shamrock fields to the west indicates that there should be no commercial recovery in case a crestal gas column <40m is encountered.
SW NE
TW
T
Top Rotliegend
Top Salt
SW NE
TW
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Top Rotliegend
Top Salt
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Fig. 3: Block 50/16 Top Rotliegend Depth Map
