Assertion: oil well | /r/HasProperty | vertical
Facets:
value: until the 1970s
type: TEMPORAL
Source sentences:
text: Until the 1970s, most oil wells were vertical, although lithological and mechanical imperfections cause most wells to deviate at least slightly from true vertical.
text: Until the 1970s, most oil wells were vertical, although lithological and mechanical imperfections cause most wells to deviate at least slightly from true vertical.