Abstract:

Sanzhao sag in Daqing oil region is found to contain many small-to middle-sized gas fields.Analysis shows that there are gas of both inorganic and organic origins and the natural gas is composed of both alkane and non-hydrocarbon gases.The later contains not only conventional non-hydrocarbon gases like carbon dioxide,hydrogen,nitrogen,and etc,but also rare gases,such as helium,argon,and even neon.Rare gases,rare-earth elements,and isotopes of some elements,can be used to determine the sources,migration mechanisms,and enrichment patterns of hydrocarbons and metal deposits.By applying this principle to the analysis of hydrocarbon gases,non-hydrocarbon gases and the isotopes of rare gases,both the hydrocarbon gases and non-hydrocarbon gases are determined to be mainly inorganic gases sourced from the deep of the earth.They occur both in the exploration area and in the developed oilfields.In recent years,Daqing Oilfield has witnessed an increase of non-hydrocarbon gases with higher production of associated gas.In addition,the geochemical behaviors of these gases also indicate an inorganic origin,quite different from that of crude.

Key words: natural gas, source, inorganic origin, Daqing oil region