Okla. Stat. tit. 60, § 319

Any instrument in writing leasing or lending or giving option to purchase any personal property, used in the digging, drilling, completing or equipping of an oil and gas well shall be void as against innocent purchasers or creditors of the lessee or bailee, unless the original instrument, or a true copy thereof, shall have been filed prior to the time the rights of any innocent purchaser or the creditors of the lessee or bailee accrue or come into being, in the office of the county clerk of the county in which the lessee or bailee keeps or uses such personal property. Laws 1941, p. 265, § 1.