Research On Paleogene Reservoir Characteristics Of Western North Of Qaidam Basin

Guided by sedimentology, reservoir geology and geochemistry theory, sedimentary characteristics, reservoir development characteristics, sand distribution and the reservoir diagenesis of the Paleogene reservoir of western north of Qaidam Basin are studied with detailed observing rock thin section, and doing relevant interior tests, to counter the difficulties of lithology and thickness changes and lack of understanding of northwest Paleogene reservoir. Based on these studies, we discuss favorable reservoir type and identify the controlling factors of reservoir development and distribution of the favorable forecast reservoir development zone.Applying mud logging, log, core, seismic and other information and combining analysis of single and multiple well profiles, sediment characteristics of this area are studied. The results show that E1+2 is the occurring phase of lake basin. During E31, lake area starts to expand, and in Xiaoliangshan and its northwest and west of Youquanzi-Temilike, lake deposition develops while river and delta deposition system develop in east of this line. E32 is the heyday period of lake basin development, and the area of lake deposit achieves the greatest.On the basis of sedimentary facies research, combining rock thin section, cathodoluminescence, fluorescence, X-ray diffraction and other test data, region diagenesis characteristics, diagenetic sequence, and reservoir development regularity are studied. The results show that deep formation has good detrital reservoir. There are four times of wide-scale diagenesis mainly in this area. The first is dolomite cementation and alternation followed by calcite cementation and alternation. The third is dissolution and the fourth anhydrite cementation and alternation. The study area has two large-scale migrations of fluid which accord with the expulsion time of hydrocarbon source rock in E31 and E32 respectively.Through thorough thermodynamics deduction, six component facies maps including calcite, dolomite and anhydrite are drew, which indicate pH and fluid ion concentrations are the main controlling factors in diagenesis of this area.Integrating analysis of deposition, diagenesis and petrophysical parameter, comprehensive evaluation and classification of this area are done with the conclusion that rive sand and delta sand depositing on ancient slopes are favorable places for oil and gas accumulation which can be the key goal of future exploration.