At approximately 1515 central time, a Mooney M20R lost engine power and was damaged in a forced landing while diverting to Sheridan Municipal Airport. The private pilot and his passenger received minor injuries. The flight was headed IFR from Walnut Ridge, Ark., Brownsville, Texas, when the pilot reported the engine was running rough. He diverted toward Sheridan and reported the airport in sight, but ended up in a field about 2.5 miles short of the runway. Examination of the airplane found that the fuel selector was on the left tank, the left tank was empty, and the right tank contained 25 gallons of fuel.