4 Va. Admin. Code § 25-101-110

Current through Register Vol. 41, No. 8, December 2, 2024

Section 4VAC25-101-110 - Casing requirements for vertical ventilation holes

A. Water-protection string.

1. Except as provided in subdivision 5 of this subsection, the permittee shall set a water-protection string to a point at least 300 feet below the surface or 50 feet below the deepest known groundwater horizon, whichever is deeper, circulated and cemented into the surface. If the cement does not return to the surface, every reasonable attempt shall be made to fill the annular space by introducing cement from the surface.

2. The operator shall test or require the cementing company to test the cement mixing water for pH and temperature prior to mixing the cement and record the results on the cement ticket.

3. After the cement is placed, the operator shall wait a minimum of eight hours and allow the cement to achieve a calculated compressive strength of 500 psi before drilling, unless the chief approves a shorter period of time. The wait-on-cement (WOC) time shall be recorded within the records kept at the drilling rig while drilling is taking place.

4. When requested by the chief, the operator shall submit copies of cement tickets or other documents that indicate the above specifications have been followed.

5. A coal-protection string may also serve as a water-protection string.

B. Coal-protection strings.

1. When any vertical ventilation hole penetrates coal seams that have not been mined out, the permittee shall, except as provided in subdivisions 2 and 3 of this subsection, set a coal-protection string. The coal-protection string shall exclude all fluids, gas and gas pressure except that which is naturally present in each coal seam. The coal-protection string shall also exclude all injected material or disposed waste from the coal seams and the vertical ventilation hole. The string of casing shall be set to a point at least 50 feet below the lowest minable coal seam above the targeted seam and shall be circulated and cemented from that point to the surface or to a point not less than 50 feet into the water-protection string or strings which are cemented to the surface.

2. For good cause shown, either before or after the permit is issued, when the procedure specified in subdivision 1 of this subsection is demonstrated by the permittee as not practical, the chief may approve a casing program involving the cementing of a coal-protection string in multiple stages, or the cementing of two or more coal-protection strings, or the use of other alternative casing procedures.

3. The chief may approve the program provided he is satisfied that the result will be operationally equivalent to compliance with the provisions of subdivision 1 of this subsection for the purpose of permitting the subsequent safe mining through the vertical ventilation hole or otherwise protecting the coal seams as required by this section. In the use of multiple coal-protection strings, each string below the topmost string shall be cemented at least 50 feet into the next higher string or strings that are cemented to the surface and be verified by a cement top log.

C. In the case of vertical ventilation holes drilled prior to December 11, 1985, through coal seams without coal-protection strings substantially as prescribed in subsection B of this section, the permittee shall retain such coal-protection strings as were set. During the life of the vertical ventilation hole, the permittee shall, consistent with a plan approved by the chief, keep the annular spaces between the various strings of casing adjacent to coal seams open to the extent possible, and the top ends of all such strings shall be provided with casing heads, or such other approved devices as will permit the free passage of gas or oil and prevent filling of the annular spaces with dirt or debris.

D. The casing program for any vertical ventilation hole designed or completed to vent from more than one stratum shall be designed in accordance with the appropriate standard practices of the industry.

E. Casing through voids shall be accomplished according to the following:

1. When a vertical ventilation hole is drilled through a void, the hole shall be drilled at least 30 feet below the void, the annular space shall be cemented from the base of the casing up to the void and to the surface from the top of the void, or it shall be cemented at least 50 feet into the next higher string or strings of casing that are cemented to the surface and be verified by a cement top log.

2. For good cause shown, the chief may approve alternative casing procedures proposed by the permittee, provided that the chief is satisfied that the alternative casing procedures are operationally equivalent to the requirements imposed by subdivision 1 of this subsection.

3. For good cause shown, the chief may impose special requirements on the permittee to prevent communication between two or more voids.

F. The permittee shall report to the chief as soon as possible when an unanticipated void or groundwater horizon is encountered that results in lost circulation during drilling. The permittee shall take every necessary action to protect the lost circulation zone.

4 Va. Admin. Code § 25-101-110

Derived from Virginia Register Volume 17, Issue 20, eff. July 18, 2001.

Statutory Authority

§§ 45.1-161.3, 45.1-161.106, 45.1-161.121, 45.1-161.254 and 45.1-161.292 of the Code of Virginia.