Administrative Rules of Montana
Department 36 - NATURAL RESOURCES AND CONSERVATION
Chapter 36.22 - OIL AND GAS CONSERVATION
Subchapter 36.22.7 - Well Spacing Units
Rule 36.22.703 - HORIZONTAL WELLS

(1) Unless otherwise modified herein, the requirements of ARM 36.22.702 shall apply to horizontal wells.

(2) For the purpose of determining the size of drilling units and the permissible location of horizontal wells, "projected depth" as used in ARM 36.22.702 means the projected true vertical depth of the deepest horizontal drainhole.

(3) A horizontal well meets the location requirements of ARM 36.22.702 if the point where the well bore first penetrates the common source of supply, the horizontal drainhole end point, and every part of the well bore lying between these points meet the minimum distance requirements from the drilling unit boundaries that would apply to a vertical well of the same projected depth, regardless of the surface location proposed.

(4) The operator of a horizontal well may designate an optional drilling unit, which must consist of two, three, or four contiguous drilling units of the size and shape otherwise authorized for a vertical well of the same projected depth. The operator must receive administrative approval of the optional drilling unit before starting to drill the horizontal drainhole. Minimum distance requirements from drilling unit boundaries that would apply to the contiguous drilling units apply to the optional drilling unit, except that such requirements do not apply to the common boundary of the contiguous units. Any operator designating an optional drilling unit under this section must apply for proper well spacing within 90 days after the completion of a well capable of production.

(5) Within 30 days after completion of a horizontal well, the operator must file with the board a complete and accurate directional survey showing the location, direction, and length of each horizontal drainhole and demonstrating that all drainholes are at locations permitted by this rule or by a board location exception order.

(6) In those cases where a horizontal well is drilled following an initial vertical penetration of the target horizon, or the horizontal well includes more than one horizontal drainhole, the completion report submitted under ARM 36.22.1011 must adequately describe each well path.