The Study On The Petroleum Properties In Northern Margin Of Qaidam Basin

Using the latest theories and methods,such as, Sequence stratigraphy, Sedimentary petrology, Seismic stratigraphy, and applicating seismic, logging, core data, this text does fine analysis and research on sequence stratigraphic framework, sedimentary facies types and evoluting rule, geochemical features of hydrocarbon rock, pattern of reservoir and capping formation. So there is a conclusion about distribution of valid mother rock, geological feaure of typical reservoir, and main factors of oil/gas playing reservior in Lenghu and Nanbaxian area, further indicating the exploration direction of large and medium size field, objective block optimization in the northern of Qaidam basin and confirm object horizon, having a constructive meaning.Main source rocks are composed of relict lacustrine fault-depression sediments of Lower Jurassic;Tertiary compressive depression deposits form the major migrating and accumulating system. The vertical migrating and accumulating are controlled by a regional. pelitic caprock of the Middle Eocene,below which,the migration and accumulation of oil-gas are mainly happened in lateral direction and vertical migrating of oil-gas only appears in layer above the capping because a migrating pathway is formed by local fault,where a double layer type can be detected within the system. The system had been primarily formed from early Oligocene which a period of forming primary oil-gas pools. A secondary oil-gas pools and dry-gas pools should be formed at the early pliocene,and the key preservation stage came during the early Quaternary.A comprehensive study on petrology, structures, facies models, facies associations and sedimentary systems in this paper shows that the main facies in Tertiary are shore-lake and shallow-lake subfacies, and lake delta facies from low-Gancaigou formation to low-Youshashan formation.Lower-Middle fresh lacustrine shale and coalmeasures with huge thickness have been found in the petroleum system of the northern Qaidam basin. These source rocks are characterized by high abundance of organic matter with mainly typeâ…¡~â…¢. The major oil and gas generation stage of the Jurassic source rocks is between J3~K,E32~N23. At that time, the existing Mesozoic paleo-uplifts and the Cenozic folds and faults, which served as oil migration routes and traps, greatly promoted the oil reservoir formation. In addition, multiple reservoir-cap compositions are confirmed in both the Jurassic and Tertiary strata.So far, Great potential for further hydrocarbon exploration remains in this area. Three preferential targets for future hydrocarbon exploration are selected, .i e. Lenghu No. 1 to No. 5 Trap, Nanbaxian-Dahonggou paleo uplift and the front of Saishiteng mountain.