You can get oil from organic-rich shales, such as those in Dorset’s Kimmeridge Clay Formation, but only if they have previously subsided deep enough (several kilometres) below overlying sediments to reach temperatures in the region of 100°C – what Professor Richard Selley of Imperial College calls “Hells Kitchen”.
Pack-a-clay, pack-a-clay, Jurassic man*,
With organic remains as full as you can.
Compress it and cook it at one hundred C
Deep down in Hell’s Kitchen – and then tell BP!