| For a long time,due to the influence of drilling stratification,it is generally believed that the Donggou Formation in the southern margin of the Junggar Basin is very thick and widely distributed.However,according to the accumulated fossil biofossil data in the past,the Donggou Formation on the Anjihai anticline may be missing,and the Donggou Formation of the Horgos anticline is only tens of meters thick.The data of the Donggou component layer currently used undoubtedly greatly exaggerates the reservoir thickness of the Donggou Formation of the Anjihai anticline and the Horgos anticline.In order to solve the fundamental problems of the Donggou Formation,this study carried out arduous and detailed field geological surveys,cross-section measurements and systematic collection of various samples.Through comprehensive and in-depth biostratigraphic research,sedimentology research,seismic stratigraphy research and electrical curve analysis of the Donggou Formation in the outcrop and underground,many important new understandings have been obtained in the division and distribution of the Donggou Formation.The study concluded that the top and bottom boundaries of the Donggou Formation in the Lutou District are clear,and the bottom boundary is bounded by the sedimentary facies of the Lianmutun Formation and the sedimentary facies of the Donggou Formation,and the overall hue of the boundary is different.The top boundary is characterized by the thick-large thick calcareous cemented conglomerate at the bottom of the Zimuquanzi Formation.The lower part of the Zimuquanzi Formation is mostly alluvial fan,and there is some difference between the braided river sediments of the Donggou Formation.After sampling and analyzing the Donggou Formation system of the Changji River,Donggou and Manas River sections,a combination of a metamorphic fossil and a group of algae fossils were discovered.There are significant differences between the two fossil combinations and the assimilated stone group in the lower part of the lower lignin group and the upper part of the purple mud spring group.The establishment of the combination sequence of the genus and the algae fossils in the lower section of the Lianmutun,Donggou and Zimuquanzi groups provides a reliable basis for accurately dividing the Donggou Formation of the drilling profile.Fossil combination sequence and lithofacies and lithology characteristics of the outcrop Lianmutun Formation,Donggou Formation and Zimuquanzi Formation,A comparative study on the division of Donggou Formation was carried out in 13 wells with large well depth in the Huomatu tectonic belt and adjacent areas.After in-depth study of fossil combination distribution,single well sedimentary facies,electrical measurement curve characteristics and seismic reflection axis termination relationship characteristics,the classification basis of the underground Donggou Formation is proposed,and the Donggou Formation drilling stratification data table is proposed.It can be used as a standard for the comparison of the Donggou Formation in the western margin of the southern margin of the Junggar Basin.Through the outcrop,drilling profile study and seismic tracing comparison,it is found that the Donggou Formation is sharply extinguished near the Anjihai River,and the sedimentary boundary of the Dongxi Formation of the Taxi River is convex to the north,and the Donggou Formation is also missing south of the Akto anticline.Therefore,the sedimentary range of the Donggou Formation in the study area is smaller than previously thought.The Donggou Formation tends to be sharpened on the Horgos anticline and the Anjihai anticline.The Donggou Formation has been missing from the Huo 002 Well,An 4 and An 7 wells,but the thickness of the Dongdonggou Formation has gradually increased.The Donggou Formation in the Manas anticline,the Tugulu anticline and the Hutubi anticline is thicker,and the northward to the Fang 3 well is slightly thinner. |
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