PURPOSE: One of the important functions of the council is to prevent the contamination of the waters of the state. In Missouri, an underground source of drinking water may occur either above or below an oil and gas reservoir. This groundwater is commonly the only source of water for irrigation and animal and human consumption. This rule provides procedures for protecting all waters of the state and to create acceptable safety standards for wells and surface installations. Plugging of wells when they are abandoned is consistent with a statewide effort to prevent contamination of waters of the state and additionally is important in areas proven to be productive using enhanced recovery methods.

1. (1) During the drilling of any well, surface casing shall be set as follows, except as otherwise required or approved by the state geologist as indicated on the approved permit to drill, deepen, plug-back, or recomplete:

   1. (A) Through all unconsolidated material plus twenty feet (20') into the underlying competent bedrock; or
   2. (B) In areas where underground sources of drinking water are present above the production or injection zone(s), at a point at least fifty feet (50') below the base of the deepest known underground source of drinking water penetrated.
2. (2) All casing materials shall be steel or other material of equal or greater strength approved by the state geologist and able to withstand collapse and burst pressures that the well might encounter.
3. (3) All wells drilled shall be completed with tubing, packer, and a string(s) of casing which shall be properly cemented at sufficient depths to protect all water, oil, or gas bearing strata and shall prevent their contents from passing into other strata. For wells drilled to producing strata at a depth of no greater than one thousand five hundred feet (1500'), an operator may set a single casing string with no tubing or packer, if the well is cemented from the bottom of the casing to the surface to seal off and protect any underground source of drinking water. The state geologist may approve other methods of cementing casing in a well.
4. (4) Cement shall be used in setting all casing or sealing off producing strata, underground porosity gas storage strata, or underground sources of drinking water. Cement shall be installed from the bottom to the top of the casing in one (1) continuous operation using pressure grouting techniques. The cement must be placed in a minimum one inch (1") annulus between strings of casing or the casing and borehole. The cement shall be maintained at surface level. Before the bottom plug is drilled or before tests are initiated, the surface casing shall stand cemented and further operations shall not begin until the cement has been in place for at least eight (8) hours and has reached a compressive strength of three hundred (300) pounds per square inch. These requirements may be modified by the state geologist.

5. (5) Multiple-completed wells. Operators may produce from more than one (1) pool through the same wellbore if separation of each pool is maintained and after application to, and approval by, the state geologist. Multiplecompleted injection and production wells may be permitted if, in addition to the requirements above, all of the following conditions are met:

   1. (A) Any offsetting production will not be adversely affected;
   2. (B) Underground sources of drinking water will not be endangered;
   3. (C) The well is continuously cemented across the injection and producing intervals; and 10 CSR 50-2
   4. (D) The well demonstrates mechanical integrity.

6. (6) The state geologist may require specific casing and cementing requirements for injection wells based on the following:

   1. (A) The depth of the underground source(s) of drinking water;
   2. (B) The nature of the injected fluids; or
   3. (C) The hydraulic relationship between the injection zone and the underground source(s) of drinking water.

7. (7) The following requirements shall apply to permitted injection wells:

   1. (A) Each operator shall equip the wellhead with a pressure observation valve and maintain equipment necessary to obtain injection pressure measurements upon inspection by an authorized representative(s) of the state geologist. For injection wells completed prior to March 30, 2016, the pressure observation valve shall be added prior to testing for mechanical integrity, or upon request of the state geologist;

   2. (B) The following tubing and packer requirements shall apply to permitted injection wells:

      1. 1. Each well permitted shall meet one

8. (1) of the following requirements:

   1. A. The well shall be equipped to

inject through tubing below a packer;

1. B. A packer run on the tubing shall be

set in casing opposite a cemented interval at a point immediately above the uppermost perforation or openhole interval. The annulus between the tubing and the casing shall be filled with a corrosion-inhibiting fluid or hydrocarbon liquid; or

1. C. A packerless or tubingless comple-

tion for injection wells drilled to no greater than one thousand five hundred feet (1500') is authorized under the provisions of paragraph (7)(B)2. or 3. of this regulation;

1. 2. Injection through tubing without a

packer is authorized if all of the following requirements are met:

1. A. The tubing shall be run to a depth

not shallower than forty feet (40') above the uppermost perforation or open hole of the injection interval;

1. B. Each wellhead shall be equipped

with a pressure observation valve on the tubing and the tubing-casing annulus; and

1. C. The operator of the tubingless com-

pletion shall maintain the well so that the mechanical integrity tests can be performed as specified in 10 CSR 50-2.055(12); and

1. 3. Injection without tubing is authorized

if all of the following requirements are continuously met during the life of the well:

1. A. The casing shall be cemented con-

tinuously from setting depth to surface;

1. B. Surface wellhead injection pressure

shall be recorded monthly and kept by the operator for five (5) years;

1. C. All pressure readings recorded

shall be taken during actual injection operations; and

1. D. The operator of the tubingless

completion shall maintain the well so that the mechanical integrity tests can be performed as specified in 10 CSR 50-2.055(12).

1. (8) In existing wells to be converted to other use, including but not limited to injection, all additional casing or recompletion shall be constructed as specified in sections (1) through (7).
2. (9) Documentation. Legible documentation of the cementing operations across all strata shall be maintained by the operator and provided to the state geologist upon request. The documentation may consist of invoices, job logs, job descriptions, or other similar service company reports.
3. (10) All points at which a well is in physical contact with a pool shall meet all minimum distance requirements as specified in 10 CSR
4. 50. For horizontal wells, a directional survey must be submitted with a well completion or recompletion report to verify points at which the well is in contact with the pool.
5. (11) Any well not constructed in compliance with requirements of this regulation shall be shut in, according to 10 CSR 50-2.060 until compliance is achieved.
6. (12) All stratigraphic test wells that are not converted to another type of well must be permanently plugged according to 10 CSR 50-2.060(3) within ninety (90) calendar days of the spud date. A single thirty (30) calendar day extension period may be granted upon written request to the state geologist. If conversion is to take place, permit modification must be submitted to the state geologist as detailed in 10 CSR 50-2.030(9) or 10 CSR 50-2.060(4) prior to conversion. The well will then be subject to all completion and location requirements for the type of well to which it is being converted.
7. (13) Permanent signage must be posted within ninety (90) calendar days of spud date at each well site indicating the well name, well number, and API number. Stratigraphic test wells and non-commercial gas wells are exempt from signage posting. AUTHORITY: section 259.070, RSMo Supp. 2015.* Original rule filed Oct. 11, 1966, effective Oct. 21, 1966. Amended: Filed Sept. 12, 1973, effective Sept. 22, 1973. Amended: Filed Oct. 14, 1981, effective Feb. 11, 1982. Amended: Filed Aug. 11, 1986, effective Oct. 27, 1986. Amended: Filed Sept. 16, 2015, effective March 30, 2016. *Original authority: 259.070, RSMo 1965, amended 1972, 1983, 1987, 1993, 1995, 2012, 2015.