No well shall be drilled within the city limits without using mud as the drilling fluid after the setting of surface casing as provided in § 170.14(b) of this chapter. Prior to the time the well reaches a total depth of 5,000 feet or the depth of the first known or encountered oil or gas-bearing horizon, whichever is the lesser depth, the weight of the mud-laden drilling fluid shall be at all times maintained at not less than ten (10) pounds per gallon. After the well reaches a total depth of 5,000 feet or the depth of the first known or encountered oil or gas-bearing horizon, whichever is the lesser depth, the weight of the mud-laden drilling fluid shall be at all times maintained at such weight as will provide a hydrostatic head of not less than five hundred (500) pounds per square inch in excess of the formation pressure. In reworking a well, a drilling fluid shall be at all times maintained at such weight as will provide a hydrostatic head of not less than five hundred (500) pounds per square inch in excess of the formation pressure.
(Ord. 39817, passed 10-2-79) Penalty, see § 170.99