If tangible property is used partly in a qualified enhanced oil recovery project and partly in another activity, the property must be primarily used to implement the qualified enhanced oil recovery project.
Because the offshore drilling platform was used in the primary and secondary development of the field and was not used for the primary purpose of implementing tertiary development of the field, costs incurred by K in connection with the acquisition, construction, transportation, erection, or installation of the offshore drilling platform are not qualified enhanced oil recovery costs. However, the costs K incurs for the additional separator are qualified enhanced oil recovery costs because the separator is used for the primary purpose of implementing tertiary development of the field. In addition, the intangible drilling and development costs K incurs in connection with drilling the injection wells are qualified enhanced oil recovery costs with respect to which K may claim the enhanced oil recovery credit.
26 C.F.R. §1.43-4