Hydrocarbon Generation Mechanism And Distribution Of Jurassic Coal Measure Source Rocks In Taipei Sag

The Taibei Sag is the main subsidence area of multistage tectonic movement in TurpanHami Basin and also the main structural unit of industrial oil flow found in the basin.The research on hydrocarbon generation mechanism and contribution degree of oil and gas of coal measure source rocks in Taibei Depression can provide more reliable basis for further exploration.Based on core sample analysis and well logging data in the study area,this thesis comprehensively analyzed the hydrocarbon generation mechanism and hydrocarbon generation potential of different types of source rocks in Shuixigou Group of Taibei Depression through organic geochemical analysis,effective source rock evaluation and hydrocarbon generation thermal simulation experiment.The following understandings were obtained during the research process:There are mainly lacustrine mudstone and coal measure source rocks in Shuishigou Group.The mudstone organic matter type of Badaowan Formation is mainly type Ⅲ kerogen of chitinous rich formation,and the mudstone of Sangonghe Formation is mainly type Ⅱ2-Ⅲkerogen of sapropelic rich formation and chitinous formation.The quality of source rocks of these two formations is better in Shengbei and Qiudong sag,but worse in Xiaocaoghu sag.The organic matter types of mudstone in Xishandao Formation are mainly type Ⅱ2-Ⅲ kerogen of Vitinite-rich formation and chitinite-rich formation.The quality of source rocks in Shengbei,Qiudong and Xiaocaohu depression is good.The organic matter type of carbonaceous mudstone is mainly type Ⅱ2 kerogen,and coal rock is mainly type Ⅲ kerogen,both of which are medium to good source rocks.All the three sets of strata have reached the mature stage,and a small part of Badaowan and Sangonghe formations are in the high mature stage.The activation energy of the three types of source rocks is normally distributed,and the main frequency is between 52 and 58Kcal/mol,indicating similar oil generation Windows.The gas activation energy distribution is discrete and lower than that of oil generation,and gas can be generated at the low maturity stage,which is a typical hydrocarbon concurrent generation.The peak hydrocarbon generation Ro of the three types of lithologic source rocks is between 0.7%and 1.0%,corresponding to the hydrocarbon generation threshold of coal and mudstone is about 3700m,and the carbonaceous mudstone is about 3300m.The carbonaceous mudstone has low hydrocarbon generation threshold and high hydrocarbon generation intensity,which is better than coal and mudstone.The total amount of source rock oil and gas in the three sets of Shuixigou Group is the largest in Xishanyao Formation,followed by Badaowan Formation and the least in Sangonghe Formation.The oil and gas reservoirs in Taibei Sag are distributed around the shoreline of the lacustrine basin with the hydrocarbon generation depression as the center and are most concentrated in the southern,western and eastern gentle slope areas.