A Los Angeles police detective assisting in a drug raid on a Van Nuys house was pushed against a wall by a large dog and accidentally shot in the thigh by another officer aiming at the animal, police said. Ronald B. Michel, 35, was in satisfactory condition at Northridge Hospital where he was expected to be for several days, Cmdr. William Booth said. Officer Lawrence R. Skiba, 39, fired the shot as 15 officers were serving a warrant to search for drugs, Lt. Charles Higbie said. The officers found 1 1/2 pounds of amphetamines and traces of heroin and cocaine, Higbie said. An occupant of the house, Stephen M. Fabricant, 32, was arrested on suspicion of possession of narcotics for sale, Booth said.