| Weihe basin is the system conformed to the zone of in the southwest of Tethys tectonic system and in southeast of The Pacific plate system and in the north of Eurasian plate. Wei river basin is a Cenozoic fault basin located in the southern margin of between the ordos basin and the qinling orogenic belt.Weihe basin has many commercial value of the resources, such as geothermal、biogas、heliumand metal minerals,etc.It is the sedimentary basin,which has a very great resources development potential and great industrial value.In the study of predecessors research results and the basis of geological data,the analysis of the geological and tectonic evolution of the basin, basing on the basis of stratigraphic division and correlation, sedimentary facies,sand body distribution,reservoir analysis and the resources distribution of integrated research,the thesis aimed to evaluate hydrocarbon source rocks and the composition of gas sample.Geochemical characteristics indicate that the hydrocarbon source rocks of the Zhang-jia-po formation have high abundance of organic matter which are awarded poor- medium level up.Good organic matter types are based on Ⅱ1 and I.When the buried depth of hydrocarbon source rocks reachede to 1845 m,it is still at the low-maturity stage.The results of source rock evaluation have shown that the wei river basin has good oil and gas potential.The water-soluble helium are given priority to with shell source of helium, and have a small amount of mantle-derived helium to join.The source rock of Helium gas is mainly for the basin basement and peripheral granite.The features of the source rock of helium gas have higher uranium, thorium, and radioactive intensity. Fracture and low-high permeability sandstone layer may be the main petroleum mmigration pathway for theaccumulations to the reservoir.Exceptional pressure seals which Gaoling group and the formation of lantian-bahe and the overlying Zhang-jia-po group formed is advantageous to rich enrichment and preservate.Four types of gas are given to biogas and bio-thermocatalytic transition zone gas,and contain a small amount of inorganic gas and pyrolysis gas at the same time.The source material of biogas related to sapropel type and humic type organic matter.Pyrolysis gas has the characteristics of coal-derived gas. The age of the gas source rock of Weinan region and xianyang region is Cambrian to the low of ordovician. And the age of the gas source rock in xi’an region is the Ordovician.The biogas resources conditionso of the gushi sunken is similar with the area of the qaidam sanhu.To calculate the resource of biogas shows that the Zhang-jia-po formation has the great geologic conditions of forming biological gas reservoirs. |
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