Discovery and significance of Mesozoic oil and gas seepages in Biru basin, northeastern Tibet, China.

During field geological survey, many oil and gas seepages had been found in Biru basin, which is located in the central-east part of Tibet Plateau. All oil and gas seepages outcropped can be classified as solid asphalt, and target horizons are in Middle-Upper Jurassic Series Lagongtang Formation and Lower Cretaceous Series Duoni Formation. Under microscope, oil & gas inclusions and nonluminous asphalt appear among framework grains of clastic rock in those two formations. By analysis of the shapes and the characteristics from outcrops, solid asphalt distributes near intensive deformation area, such as fault zone and fracture zone. Cenozoic structure in Biru basin had been undergone more intensive deformation and bigger uplift or much more denudation than the rest basins of the same kinds properties in the central of Tibet Plateau. Therefore, many problems would be faced during plateau oil-prospecting in the future, and impact of structural evolution and tectonic landform action on hydrocarbon-bearing pool should be stressed.