CHARACTERISTICS OF CAP ROCKS IN CUOQIN BASIN,TIBET

China National Petroleum Corporation has conducted petroleum exploration in Qinghai-Tibetan Plateau since 1994.Several sets of source rocks have been discovered after 4 years' geological reconnaissance in the Cuoqin Basin of northern Qinghai-Tibetan Plateau.The cap rocks essential to the oil and gas preservation have been evaluated from their lithology,thickness and microstructure.Mudstones,volcanic rocks and carbonates are suggested to be the dominant cap rocks for oil pools,then come the dense siltstones.