Okla. Stat. tit. 16, § 37

All deeds, mortgages, oil and gas leases, powers of attorney and other instruments of writing for the conveyance or encumbrance of any lands, tenements, or hereditaments situated within this state, heretofore executed and acknowledged or proved in any state, territory, District of Columbia or country in conformity with the law of such state, territory, District of Columbia or country, shall be as valid as if executed within this state in conformity with the provisions of the laws of this state. Provided this act shall not validate any acknowledgemts fraudulently obtained.