RE: Actual production Numbers17 Aug 2020 17:23
Mirasol,
Glad you reminded us about Wytch Farm. The geology of the accumulation clearly demonstrates why ‘young’, Tertiary-age structures in the Weald and Wessex Basins are dry because they formed AFTER oil was generated in the source kitchens. In contrast, structural traps present BEFORE oil was generated, like Wytch Farm, tend to be full of oil.
Anglo-Persion figured this out in Iran/Iraq before moving on to licence the whole of Albania to discover `Europe’s biggest (1 bnbbl) onshore oilfield, Patos-Marinza, in 1938. At roughly the same time they looked at UK and drilled Ashdown-1 on the crest of the enormous Weald anticline, only to realise it had formed after peak oil generation. Known as BP by then, two other dry holes followed, Portsdown-1 and Arreton-1 - both failures, but with weak shows. The only success was Broadbench-1 - which became known as Kimmeridge-1, still producing today.
BP’s chief geologist at the time reviewed Arreton-1 (1952) and concluded ‘only very slight traces of oil were encountered and the lack of success is ascribedto early early migration of oil towards the edges of the basin before formation of the Arreton structure’.
They had mapped the structure on surface geology and tested 2 Purbeck intervals, and the basal Purbeck - all with no flow nor reservoir pressure. Same for one test in Inferior Oolite.
Later, Gas Council drilled Arreton-2 (1974) at exactly same place, but were actually looking for the eastern extent of the Bridport and Sherwood Sandstones - but they are absent at Arreton.
Strangely, trap timing is barely mentioned in UKOG’s CPR despite it being the single most important fact for discovery.
The American philosopher Santayana once said “those wearing red trousers who do not learn from the past are doomed to repeat it”.