The Thermal Evolution Indicated by Integrated Methods: Implication for Source Rocks Maturation and Petroleum Prospective in the Meso-Cenozoic Basins of the Tibetan Plateau

Chen, Honghan; Wu, You

Although the tectonothemlal evolution of the Tibet Plateau, such as uplift mechanism, continental massive convergence and intracontinental conduction, middle-lower crustal flowing and magmatic activities, has been extensively studied, the thermal history in the many hinterland Meso-Cenozoic basins has seldom been discussed. Integrated with all the published thermal data in Changthang, Qamdu, Tsochen, Biru and Gamba-Dingri basins, this research systematically measured 88 fluid inclusion samples to obtain the homogenization temperatures of diagenetic aqueous inclusions for the calculation of the paleothermal gradients. The geological ages for each paleothermal gradient were determined by homogenization temperature projection on burial history charts. And the Meso-Cenozoic paleothermal gradient evolution trends for each basin are then established, which indicates that the basins had the relative lower averaged thermal gradients (<3.0 degrees/100m) since the Mesozoic to the Paleocene corresponding to their evolution stages of passive continental margin, backarc basin and foreland basin; but had a dramatic and uneven increasing of averaged thermal gradient (~6.5 degrees/100m) during the Neogene and Quaternary corresponding to the Tibetan uplifting and the Mesozoic marine basins evolving into residual basins. Undoubtedly, the paleothermal gradient increasing not only influenced the source rock maturities, but also led to the cracking of accumulated oil and high mature gas generation within the Mesozoic marine source rocks. The data of vitrinite reflectance and mature parameters of oil seepages further confirm the late thermal event played a very important role of the Mesozoic marine source rocks. Finally, the petroleum exploration suggestions are that there is some potential for oil exploration in areas of relative lower thermal gradients, and in most "hot" areas only gas could be expected.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013