The Santanghu The Geological Characteristics Of The Basin And Basin Thermal Evolution

This thesis represents the principle that the oil and gas were controlled by the structural evolution of oil and gas-bearing basin, the study of oil and gas-bearing basin must be systematic, dynamic and comprehensive. Based on preceding statements the geological history and thermal history of the basin were made with systematic study by means of computer modeling and multi-testing methods.Santanghu basin , located in the edge of the southern Siberian plate, has the double basements of the pre-Cambrian crystalline basement and the palezoic metamorphic basement of volcanic-sedimentary rocks. The basin has three evolutionary stages including intracontinental rift basin in P1-P2, down basin in T2+ 3-K and the strong trust-orogeny process in N-Q.According to the unconformity contact relationship and sedimentary components, Santanghu basin is divided into four tectonic sequence such as : O-C tectonic sequence of basement ,Pi-P3 tectonic sequence, T-K tectonic sequence and N-Q tectonic sequence. There have a certain correlation between Sangtanghu basin and other basins in region. The basin was undergone multi-period of tectonic movement such as HercynianN Indo-Chinav Yanshanian and Himalayan . Sangtanghu basin is a superimpose basin which deposited terrestrial sediments of Mesozoic Cenozoic and has a complicated structural evolutionary history.In the paper, it is discussed the influential factors to the geothermal temperature of Santanghu basin as well as evaluated the effect of volcanic activities in early and middle Periman. Based on many thermal indicators such as vitrinite reflectance, biomarker and fluid inclusion , the study of basin thermal history was taken . Easy %Ro model can be adopted to carry out the inversion of thermal history. The geothermal gradients in Early Permian-Middle Permian was between 4.11 to 5.2℃ /100m; from Triassic to Jurassic, geothermal gradients was in range of 3.38℃ /100m-3.93℃/100m, 3.12℃/100m-3.59℃/100m respectively in the north andsouth of Tiaohu depression, and about 2.56℃/100m-3.86℃/100m in Malang depression.There are two main stages of oil and gas migration and accumulation: late indo-china epoch and late Yanshanian epoch. The early volcanic activity accelerate the thermal maturity of source; rocks in Early and Middle Periman . The thermal events of late Hercynian movement and late Yanshanian movement has great effects on the maturation of source rocks. The source rocks of Carboniferous and Early Periman generated oil in Middle Triassic. The source rocks in middle Periman reached the oil threshold in Mid-Late Jurassic. The source rocks in Jurassic havn't reached the oil threshold.