RE: Malcy Comment 223 Feb 2021 17:46
Headinsand
The ‘expert’ responsible for the latest seismic interpretation and presentation about Lidsey seems to have enlarged the accumulation by including an area which is part of the Tertiary-age Portsdown Inversion trend. As experienced Weald Basin petroleum geologists know, these Tertiary-age structures formed after oil had been generated and expelled and are all dry.
Years ago D’Arcy (BP) drilled dry wells in the centre of the Weald anticline at Ashdown and it dawned on everyone that the rocks there had originally been part of a huge syncline. In the 1980s Carless plastered the margins of the basin with 48-channel, 12-fold Vibroseis in a four-year programme of drilling and seismic which led to discoveries at Humbly Grove, Herriard, Hordean, West Dean, Storrington and so on.
Huge surface anticlines like Portsdown and Arreton, on the Isle of Wight, were proved dry in the 1950s, again by D’Arcy.
The key success factor was only to drill Middle Jurassic structures where the isopach between the Gault Clay and the Great Oolite was defined on seismic as a ‘paleo-thin’ -i.e. a structure available to receive basin-centre oil charge. That’s why Carless drilled at Lidsey in 1987. But that’s only the seismic problem; far more risk in involved with the permeability of the Great Ooolite - which is almost non-existent at Lidsey. In carbonate reservoirs, early petroleum charge is crucial to prevent deterioration of the reservoir.
Experience suggests Carless got it right - small oil in place and non-commercial. I’m just amazed after more than 30 years that it’s worth wasting more money on Lidsey. And where will Angus find a seismic crew to acquire a single new seismic line - there simply aren’t any in UK.