Oregon Revised Statutes Revenue and Taxation § 324.310

(1) Require any producer of oil or gas, purchaser of oil or gas, agent or employee of any producer or purchaser or the owner of any royalty interest in oil or gas to furnish any additional information considered by the department to be necessary for the purpose of correctly computing the amount of tax imposed by this chapter;

(2) Examine the books, records and files of any producer, purchaser or royalty owner;

(3) Administer oaths and compel the attendance of witnesses and the production of books, records and papers of any person by subpoena; and

(4) Make any investigation considered necessary to a full and complete determination as to the amount of production from any oil or gas location, or of any producer of oil or gas, and as to the correct determination of taxes due under this chapter.