A well drilled as part of an appraisal drilling program.
A well drilled for the purpose of determining the size of an oil or gas discovery.
A well drilled to confirm the size or quality (commercial potential) of a hydrocarbon discovery. Before development, a discovery is likely to need at least two or three such wells.
A well drilled as part of an appraisal drilling programme which is carried out to determine the physical extent, reserves and likely production rate of a field.
a well drilled to further confirm and evaluate the presence of hydrocarbons in a reservoir that has been found by a wildcat well.
a well or wells drilled to follow up a discovery and evaluate its commercial potential.