During initial climb after takeoff, the pilot noticed oil streaming out from the oil filler access door on the right engine cowling. He elected to continue climbing and make a tear drop turn back to the airport and land in the opposite direction from which he had departed. He announced his intentions on UNICOM radio. Another pilot responded that he was presently on the runway but would clear it as soon as possible. The subject pilot then decided to make a go around. During this time, the right front seat passenger stated he observed flames in the right engine cowl. The pilot shut down the engine and feathered the propeller. He added full power to the left engine and retracted the landing gear and flaps. He was unable to maintain altitude and decided to make a forced landing straight ahead in an open field. He had to pull up once to avoid a power line and maneuver to avoid an antenna. He made a successful forced landing and all occupants exited. The flames quickly spread and the aircraft was consumed by ground fire.