Subsidence History Of Mesozoic-Cenozoic In The North Margin Of Junggar Basin And Its Application For Reservoir Formation

Junggar basin is a large intra-continental multiple superimposed basin which is developed on the basement of Early Hercynian orogeny. And, much difference is existed in the mechanism, especially during the Carboniferous and Permian, due to its tectonic location among Siberia plate, Kazakhstan plate and Tarim plate. It is very important significance to the basin mechanism, the maturity and hydrocarbon generation period of source rock and the reservoir formation, that studying subsidence history for this area because of the lower degree of exploration and research.Backstripping technique is used in the recovery of subsidence history of wells on the basis of erosion thickness that is calculated by the interval transit-time of mudstone and the sedimentation rate. The results of subsidence history analysis can be used to analyze the features of subsidence and burial in various evolutionary stages of basin through the subsidence rate and sedimentation rate. This is necessary for discussing the mechanism of Junggar basin in Mesozoic and Cenozoic, studying the burial depths and the hydrocarbon generation ability of the Jurassic source rock in geohistory, analyzing the subsidence and uplift denudation of basin at the main hydrocarbon expulsion time, and predicting the potential reservoir formation time in this area.The result of subsidence history demonstrates (1) the north margin of junggar basin is under the compressing environment in general during Triassic, exception with a few wells which indicate some features of rifting basin perhaps due to the simultaneous sedimentary activity of the paleo-faults in the middle of the margin; (2) the regular subsidence curves of Jurassic suggest the fast-slow-fast subsiding features; (3) there is little chance to capture the hydrocarbon from the depression of Ma-hu or the west of Pen 1 well adjoin this area; and (4) the end period of Jurassic and Cretaceous will become the most important potential reservoir formation time in the north margin of junggar basin if the enough hydrocarbon can be provided by the source rock in the Wu lun-gu depression.