松辽盆地北部昌德东气藏CO2成因的地球化学判据

CO2气藏中CO2的百分含量、CO2伴生的烃类气体含量、稀有气体的含量及同位素、CO2产出的地质背景、δ13CCO2以及伴生甲烷同系物的碳同位素系列等特征都可以用来对CO2成因进行判别。昌德东气藏天然气中的CO2含量最高(89%~90%),CO2的碳同位素值为-4.06‰~-6.61‰,落在无机成因区,3He/4He值为3.9×10-6和4.5×10-6,介于幔源与壳源之间,伴生甲烷同系物的碳同位素都呈倒序排列,具有无机成因气负碳同位素系列的特征。对其更具体的母源区的判别有赖于对松辽盆地北部深部地质结构的研究及CO2/3He等新的CO2成因判据的探索。

Geochemical Criterion of CO2 Origin of Changdedong Gas Deposit in North of Songliao Basin

Several characters of CO_2 deposits can be used to judge the origin of CO_2, such as the percent of CO_2, the percent of companion hydrocarbon, the percent of inert gases and their isotopes, geology background of CO_2 generation, δ~(13)C_(CO_2) and carbon isotopes of companion methane homologous series. The percent of CO_2 in Changdedong gas deposit is 89%～90%, δ~(13)C_(CO_2) is -4.06‰～-6.61‰,which is belong to the area of inorganic origin,~3He/~4He is 3.9×10~(-6) and 4.5×10~(-6),which is between the mantle origin and crust origin. Carbon isotopes of companion methane homologous series reverse order, which have the character of inorganic origin. The judgement of more detail origin of this CO_2 deposit is dependent on the researching of deep geology structure of northern Songliao basin and exploring new geochemical criterions such as CO_2/~3He,etc.