| Changling Seg lies in the south of Songliao Basin, which is the secondary fault depression in the Central Seg of Songliao Basin. It is one of the segs rich in oil and gas, and the area is about 8000 km~2.The basement is metamorphite and granite from Permo-Carboniferous,the sedimentary caprocks are from upper Jurassic, Cretaceous, Tertiary and Quaternary from lower to upper. The upper Jurassic is major coal-bearing pyroclast terrestrial deposit formation, the Cretaceous is major terrestrial clastic deposit formation, the Tertiary is major terrestrial clastic deposit formation which distributes in the western of the basin, the Quaternary usually distributes the whole basin. The strata are Huoshiling formation, Shahezi formation, Yingcheng formation, Denglouku formation, Quantou formation, Qingshankou formation, Yaojia formation, Nengjiang formation, Sifangtai formation and Mingshui formation from lower to upper.The evolution of structure in Changling Seg is divided into four stages. The deposition cover formed during the stage of fault depression and the stage of sag. The cover is divided into upper and lower sets of strata at the reflector (T3), which are individually called the strata of fault depression and the strata of sag. The characters between these two set of strata are obviously different. The reservoirs of Changling Seg is divided into two oil systems depending upon layers of fault depression and the differences of two sets of structure layers of the Seg. The main three of reasons are the differences of developing characteristics of oil sources rocks of the oil systems, different migrations and the differences of generating factors of reservoirs. Theses conditions and differences of reservoir generation control the formation and distribution.During the stage of fault depression, the structure was stable, the area of lake basin was big and the water is deep, so the formed source rock of hydrocarbon has the feature of area wide, distribution stable, quality high and generation of hydrocarbon potential. The system of reservoir mainly developed in the pattern of self generation and self storage and the pattern of upper generation and lower generation.According to the characteristics of generation, storage and cover, Changling Seg is vertically divided into the upper bearing-hydrocarbon system, medium bearing-hydrocarbon system and the lower combination of bearing-hydrocarbon system. They are responded to three sets of generating hydrocarbon layers. The upper combination, Nenjiang Formation, reservoirs are autogeny and self-storaged; the medium, Yaojia Formation, Qingshankou Formation, oil is laterally migrated to form reservoir, the lower combination, Upper Denglouku Formation, Member One of Quantou Formation to Member Three, oil is migrated vertically, and in Shahezi Formation and Yingcheng Formation, the hydrocarbon zone is to be formed with lateral migration of hydrocarbon in a short distance.There is abundant resources of natural gas in Changling Fault Depression as in the north of Songliao Basin.The history of sedimentation and tectonic evolution forms the uniform entirety with the southern Basin. There exists rich resources of oil and gas in the strata of faulty depression of Changling Seg with substances forming middle and large scale reservoir of oil and gas. Dongling Structure lies in the pointing area of the migration and accumulation of oil. It is a complex trap with successive long period. The characteristics are the area of fold large, combination of reservoir matching much better, and the oil-and gas-bearing reservoir systems much more, with the geological condition to be large scale of reservoir.It is proved that there is a prospective foreground in the deep igneous rock in Changling Seg, from the point of view of volcanic rock adding tectonic, and combining the reservoir feature of the igneous rock in Xujiaweizi Fault Depression as well as the break through of the igneous rock in the well of Changshen 1 of Yingcheng Formation of Haerjin Structure Zone. |
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