油气源对比的原则暨再论长庆气田的气源——兼答《论鄂尔多斯盆地中部气田混合气的实质》

Rules of petroleum source correlation and their application in the Changqing gas field-A reply to "Feature of mixed gas in central gas field of Ordos basin

油气源对比应遵循的原则 ,首先是能够解释地质实际 ,其次应符合烃源岩评价结果 ,再次是合理解释地球化学对比指标。确定混源气的主要来源时应考虑不同种类样品所代表的储量的大小 ,并应合理确定端元气中次要组分对比指标的浓度和特征值。长庆气田奥陶系碳酸盐岩气藏天然气“主要来自石炭系”的观点证据更充分 ,可以合理解释气藏的分布 ,符合石炭系各类烃源岩的评价结果 ,并且能够解释奥陶系气藏气地球化学指标与石炭 二叠系的差异 ;相反 ,“奥陶系自生自储”的观点不能合理解释奥陶系气藏的分布 ,不符合奥陶系碳酸盐岩生烃评价结果 ,并且不能提供排他性的地球化学证据。

Works on petroleum source correlation should comply with the following rules: the correlation results should first conform geologically to petroleum distribution, then conform to the evaluation of source rock. When to determine the main source from two sets of source rock of a gas reservoir, reserve amount represented by samples with each type of geochemical indices should be taken into account, instead of the numbers of samples. The concentration and geochemical indices of the remark minor components in each end member of mixing gas should be defined reasonably. Of the two different results of gas source correlation of the Ordovician gas reservoir of the Changqing gas field, the opinion of 'Carboniferous source' conform to the distribution of gas pools and the evaluation of different types of source rock in Carboniferous, and can explain the difference between the geochemical indices of Ordovician pool gas and those of Permo Carboniferous pool gas; while the opinion of 'Ordovician source' is contradicting to both the Ordovician gas reservoir distribution and Ordovician hydrocarbon potential evaluation. Natural gas in Ordovician reservoir is generated mainly from Carboniferous instead of from Ordovician.