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HMRC internal manual

Oil Taxation Manual

Capital Gains: Undeveloped Areas - Appraisal Work

This is defined at TCGA 92\S196(6):

Appraisal Work in relation to any area means work carried out for the purpose of ascertaining the extent or characteristics of any oil bearing area the whole of part of which lies in the area concerned, or what the reserves of oil of any such oil bearing area are.