Mont. Code § 82-11-208
An order providing for unit operations may be amended by an order made by the board in the same manner and subject to the same conditions and notice as an original order providing for unit operations; however, if such an amendment affects only the rights and interests of the owners, the approval of the amendment by the persons owning interests which are free of costs, such as royalties, overriding royalties, and production payments, is not required, and an order of amendment may not change the percentage for the allocation of oil and gas as established for any tract by the original order, except with the consent of all persons owning oil and gas rights in the tract, or change the percentage for the allocation of cost as established for any tract by the original order, except with the consent of all owners in the tract.
§ 82-11-208, MCA