2 of 2 codes

Horizontal well flag — 2 of 2 codes, each with its meaning, normalised form and the years it is valid for
Code Means Normalised Valid
Y Horizontal The permit is for a horizontal wellbore. Horizontal always
N Vertical Anything that is not 'Y', including blank. Vertical always

Where this mapping came from: OilGasDataProcessing process_permits.horizontalOrVertical