Intermediate casing must be set to protect fresh water if surface casing was set above the base of the deepest fresh water, if additional fresh water was found below the surface casing shoe, or both. Intermediate casing used to isolate fresh water must not be used as the production string in the well in which it is installed, and may not be perforated for purposes of conducting a hydraulic fracture treatment through it.
When intermediate casing is installed to protect fresh water, the operator shall set a full string of new intermediate casing at least 100 feet below the base of the deepest fresh water and bring cement to the surface. In instances where intermediate casing was set solely to protect fresh water encountered below the surface casing shoe, and cementing to the surface is technically infeasible, would result in lost circulation, or both, cement must be brought to a minimum of 600 feet above the shallowest fresh water zone encountered below the surface casing shoe or to the surface if the fresh water zone is less than 600 feet from the surface. The location and depths of any hydrocarbon-bearing zones or fresh water zones that are open to the wellbore above the casing shoe must be confirmed by coring, electric logs, or testing and must be reported to the Department.
In the case that intermediate casing was set for a reason other than to protect strata that contains fresh water, the intermediate casing string shall be cemented from the shoe to a point at least 600 true vertical feet above the shoe. If there is a hydrocarbon-bearing zone capable of producing exposed above the intermediate casing shoe, the casing shall be cemented from the shoe to a point at least 600 true vertical feet above the shallowest hydrocarbon-bearing zone or to a point at least 200 feet above the shoe of the next shallower casing string that was set and cemented in the well (or to the surface if less than 200 feet).
225 ILCS 732/1-70