Hailaer Basin Thermal Evolution History Of Study Of History And Hydrocarbon Accumulation

By principles of integrated, dynamic and comprehensive basin analysis, research were made in Hailaer basin using geological, mathematical, geophysical and geochemical methods. Progresses are made according to research of thermal evolutional history and oil-gas reservoirs generation history in the Hailaer basin.On the regression analysis from large numbers of thermometric data, results show that the Hailaer basin is a middle-temperature style basin, present geothermal gradients change little in different areas, average value is 3.0℃/100m, average value of thermal flux is 59mw/m2. The thermal gradient distribution in Hailaer basin is controlled by large-scale strike-slip fault and depression extension. In the Southern depression, the depression extension is large and thermal gradient value is higher.Thermal evolutional degree of contemporary layer in the south basin is higher than that in the north. In different depression, thermal evolutional degree in the center part of contemporary layer is higher than that in the fringe part. Large depressions in northern basin, the hydrocarbon source rocks of Damoguaihe formation is in immature-stage, while in the southern basin, the same hydrocarbon source rocks is in the low mature-stage. Similarity, hydrocarbon source rocks of Nantun formation in northern depression, its maturity is in the immature to low mature stage, partly in high-mature stage, becomes the main oil production layer in the Hailaer basin and southern depression is the main oil-gas prospecting areas.The average paleogeothermal gradient in the Hailaer basin is between 3.46-4.20 ℃/100m, which is obvious higher than present thermal gradient due to the recovery of thermal evolutional history by means of many kinds of paleothermometric methods, results also indicate that the values of paleothermal flux is higher than that of present values, and temperature contrasts between historic and present implies that the paleothermal in lager depressions are higher that the present.The max paleogeothermal values of hydrocarbon source rocks were reached in the late Yimin formation period, paleogeothermal field controlled maturity of hydrocarbon source rocks.Analysing generation hydrocarbon process of hydrocarbon source rocks on reflectance of vitrinite evolutional history and caseate generation hydrocarbon history, hydrocarbon source rocks in most of depressions have experienced two oil and gas generation periods. Research were made on the oil-filling history of the Hailaer basin, using the methods of the dating of illite, saturation pressure and homogenization temperatures fluid inclusion combining with thermal evolutiona history and burial history research . Results show that the forming time of oil-gas reservoirs have two stages: the first is in the late Yimin formation sedimentary stage; the second is from Qinyuangang formation sedimentary to now. The first stage is the most important oil and gas generation stage hi Hailaer basin. Since Qinyuangang formation sedimented, oil and gas have happened to be adjusted again due to the east-west directional extrusion and reversion, and secondary generation oil and gas poured into the traps and formed new oil-gas reservoirs,, Present oil-gas seservoirs are the adjustive result since Qinyuangang formation sedimented, this stage is important for oil and gas exploration in Hailaer basin.