Western Energy Resources reported a net loss of $31,356 for the third quarter, compared to a loss of $498,884 for the year-earlier period. Revenues rose 85% to $97,889 from $52,887 a year ago. Richard Johnson, president, said the sales increase was due to the acquisition of the assets of Petro Energy Management Corp., a privately held oil and gas company, as well as rising oil prices. Net loss for the nine months of 1987 was $106,061, compared to a loss of $621,679 a year earlier. Revenues for the first nine months fell 4.2% to $190,131 from $198,577. Western Energy, based in Mission Viejo, is an independent oil and gas company.