NAC534A.490. Abandonment of geothermal or injection well.

For abandonment of a geothermal or injection well, the following provisions apply:

     1. Cement used to plug the well, except cement used for surface plugging, must be placed in the hole by pumping through drill pipe or tubing. The cement must consist of a mix which resists high temperatures.

     2. Cement plugs must be placed in the uncased portion of wells to protect all subsurface resources. These plugs must extend a minimum of 100 lineal feet above the producing formations and 100 lineal feet below the producing formations or to the total depth drilled, whichever is less. Cement plugs must be placed to isolate formations and to protect the fluids in those formations from interzonal migration.

     3. Where there is an open hole, a cement plug must be placed in the deepest casing string by:

     (a) Placing a cement plug across the guide shoe extending a minimum of 100 lineal feet above and below the guide shoe, or to the total depth drilled, whichever is less; or

     (b) Setting a cement retainer with effective control of back pressure approximately 100 lineal feet above the guide shoe, with at least 200 lineal feet of cement below, or to the total depth drilled, whichever is less, and 100 lineal feet of cement above the retainer.

     4. If there is a loss of drilling fluids into the formation or such a loss is anticipated or if the well has been drilled with air or another gaseous substance, a permanent bridge plug must be set at the casing shoe and capped with a minimum of 200 lineal feet of cement.

     5. A cement plug must be placed across perforations, extending 100 lineal feet below, or to the total depth drilled, whichever is less, and 100 lineal feet above the perforations. When a cement retainer is used to squeeze cement into or across the perforations, the retainer must be set a minimum of 100 lineal feet above the perforations. Where the casing contains perforations at or below debris or collapsed casing, which prevents cleaning, a cement retainer must be set at least 100 lineal feet above that point, and cement must be squeezed in the interval below the retainer.

     6. The approval of the Administrator must be obtained before casing is cut and recovered. A cement plug must be placed in such a manner as to isolate all uncased intervals and guide shoes that are not protected by an inner string of casing. The plug must extend a minimum of 50 feet above and below any such interval or guide shoe.

     7. All annular spaces extending to the surface must be plugged with cement.

     8. The innermost string of casing which reaches ground level must be cemented to a minimum depth of 50 feet below the top of the casing.

     9. The hardness and location of cement plugs placed across perforated intervals and at the top of uncased or open holes must be verified by setting down with tubing or drill pipe a minimum weight of 15,000 pounds on the plug or, if less than 15,000 pounds, the maximum weight of the available tubing or drill pipe string. If a cement retainer or bridge plug is used to set the bottom plug, a test is not required for that interval.

     10. The surface must be restored as near as practicable to its original condition.

     11. Any interval that is not filled with cement must be filled with good quality, heavy drilling fluids.

     (Added to NAC by Comm’n on Mineral Resources, eff. 11-12-85)