Geochemical Characteristics of Light Hydrocarbons in Crude Oils from No.1 Area of Central Junggar Basin

System comparative studys of the distributions and compositions of light hydrocarbons in crude oils from No.1 area and adjacent oilfields in Junggar basin show that abundant methyl cyclichexane exists in the crude oils with methyl cyclichexane index(MCHI) more than 50% and higher Pr/Ph ratio,which are very different from crude oils from Shixi and Mobei oilfields.This implies that terrestrial matter from higher plants plays a significant role during the generation of the crude oils from No.1 area,and it is consistent with the results of the literature by geochemistry methods of biomarkers and carbon isotope.According to the relationship between the 2,4-DMC5/2,3-DMC5 ratio and the temperature of oil generation,it suggests that the maturity of crude oils from No.1 area is higher than those from Shixi and Mobei oilfields,indicating higher maturity of the organic matter in main source rocks of central Junggar basin.Therefore,it′s very useful of the light hydrocarbon from crude oils for the study of its origin,causes and maturity.