ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables. Wellhead pressure The pressure exerted by the fluid at the wellhead or casinghead after the well has been shut off for a period of time, typically 24 hours Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV.