PURPOSE: This rule provides for the protection of both surface water and groundwater. Drilling muds, oil and water recovered from drilling or testing operations must be disposed of so that pollution of surface soil, ponds and streams is avoided. Fresh water strata are protected by casing set below the deepest zone that might contain fresh water. Dry holes must be plugged and abandoned in a manner that subsurface salt water or mineralized water will be confined to the stratum in which it occurs. Similarly, each oil or gas stratum penetrated by a well must be permanently sealed when abandoned to prevent contamination of fresh water supplies and also to prevent damage by water of any oil or gas stratum capable of producing in paying quantities. In certain logging procedures, a radioactive source (in a probe or sonde) is lowered into the borehole to provide certain subsurface data useful in exploration for oil and gas. Should this radioactive source contained in a logging tool be lost, certain procedures are prescribed to prevent the accidental or intentional mechanical disintegration of the radioactive source. Further, there are provisions for marking the well site permanently as a warning that a radioactive source has been abandoned in the well.

1. (1) Before beginning abandonment work on any well whether it is a drilling well, or a well drilled for oil or gas, for geologic information, or for gas storage, or for any other purpose, notice of intention to abandon the well shall be filed with the state geologist on approved form OGC-6. The notice shall include the details of the proposed abandonment procedure and whether any logging tool containing a radioactive source is being abandoned (see section (8) of this rule for radioactive source abandonment procedure). If necessary to avoid rig downtime, oral permission to abandon dry holes may be obtained by informing the state geologist of proposed abandonment procedures.
2. (2) In lieu of prior notice and approval by the state geologist (form OGC-6) the operator may elect to plug the hole from total depth to within plow depth of the surface with cement slurry, being no less than sixteen (16) pounds per gallon density. In such event, form OGC- 7 shall be forwarded to the state geologist within forty-eight (48) hours after completion.
3. (3) Before any well is abandoned, it shall be plugged in a manner which will confine permanently all oil, gas and water in the separate strata originally containing them. The plugging operation shall be accomplished by the proper use of mud-laden fluid, cement and plugs, used singly or in combination as may be approved by the state geologist.
4. (4) Drill holes in formations which contain oil or gas or from which oil or gas have been produced, or that have been used for injection, shall be plugged by placing cement from the base of the formation to a point no less than twenty-five feet (25') above the top of the formation.
5. (5) Appropriate means shall be taken to eliminate movement of surface water into a plugged well and to prevent pollution of subsurface strata.
6. (6) Casing shall be cut off below plow depth except as may be approved by the state geologist to allow for the conversion of a well to a water supply well for use by a landowner. A well conversion agreement (form OGC-8) is available for use by the operator and landowner in these instances. 10 CSR 50-2
7. (7) Within thirty (30) days after the completion of abandonment, the prescribed plugging record, form OGC-7, shall be executed and submitted to the state geologist.

8. (8) Before a radioactive source may be abandoned, the person, firm or corporation proposing the abandonment shall notify the state geologist. Wells in which radioactive sources are being abandoned should be mechanically equipped so as to prevent the accidental or intentional mechanical disintegration of the radioactive source.

   1. (A) Sources being abandoned in a well should be covered with no less than a fifty feet (50') standard-color-dyed cement plug on top of which a whipstock should be set. The dye is to alert the re-entry operator prior to encountering the source.
   2. (B) In wells where a logging source has been cemented in place behind a casing string and above total depth, upon abandonment a standard-color-dyed cement plug should be placed opposite the abandoned source and to extend fifty feet (50') above and fifty feet (50’) below with a whipstock placed on top of the plug.
   3. (C) In the event the operator finds that after expending a reasonable effort, because of hole conditions, it is not possible to abandon the source as prescribed in subsections (8)(A) or (B) of this rule, s/he shall seek the state geologist’s approval to cease efforts in this direction and obtain approval for an alternate abandonment procedure.
9. (9) Upon permanent abandonment of any well in which a radioactive source is left in the hole, and after removal of the wellhead, a permanent plaque is to be attached to the top of the casing left in the hole in a manner that re-entry cannot be accomplished without disturbing the plaque. This plaque would serve as a visual warning to any person re-entering the hole that a radioactive source has been abandoned in place in the well. The plaque should contain the trefoil radiation symbol with a radioactive warning and should be constructed of a long-lasting material such as monel, stainless steel or brass.

10. (10) Monies deposited in the Oil and Gas Remedial Fund may be used by the council to plug those oil, gas and injection wells that have been abandoned and have not been plugged according to the council’s rules, subject to the following guidelines:

    1. (A) Wells covered by a forfeited bond shall receive first priority; and
    2. (B) Other wells shall receive secondary priority on the basis of their potential for groundwater contamination or other damage in the order recommended to the council by the state geologist.

AUTHORITY: section 259.060, 259.070 and 259.190, RSMo 1986.* Original rule filed Oct. 11, 1966, effective Oct. 21, 1966. Amended: Filed Sept. 12, 1973, effective Sept. 22, 1973. Amended: Filed Dec. 12, 1975, effective Dec. 22, 1975. Amended: Filed Sept. 10, 1979, effective Feb. 11, 1980. Amended: Filed Oct. 14, 1981, effective Feb. 1, 1982. Amended: Filed Sept. 13, 1983, effective Dec. 11, 1983. *Original authority: 259.060, RSMo 1965, amended 1972; 259.070, RSMo 1965, amended 1972, 1983; and 259.190, RSMo 1965, amended 1983.