柴达木盆地三湖地区储盖组合有效性对生物气富集的控制作用

柴达木盆地东部三湖地区是生物气富集区。但是,已发现的生物气不仅在不同构造间的分布极不均匀,同一气田不同储盖组合(按天然气、地层水特征划分的生物气储集单元,相当于气藏)生物气的富集程度也有很大差别。为了揭示储盖组合有效性对生物气富集的控制作用,计算了已发现气田各储盖组合的排替压力差和相对散失量,并将它们与生物气储量、单储系数进行了对比分析。结果发现:排替压力差较大的储盖组合其生物气富集程度高,反之则富集程度低;相对散失量较大的储盖组合生物气富集程度低,反之富集程度高。排替压力差与相对散失量是表征储盖组合有效性的定量参数,它们与生物气富集的关系反映了储盖组合有效性对生物气富集的控制作用。

Controlling effect of reservoir-cap combination quality on richment grade of biogas in Sanhu area of the Qaidam Basin

Sanhu area in eastern part of the Qaidam Basin is rich of biogas, but its distribution in the area is hetero-equilibrium not only in different tectonic locations but also in different reservoir-cap combinations of same biogas field. In order to find the controlling effect of reservoir-cap combination quality on distribution feature and rich grade of biogas in the area, displacement pressure differences and biogas diffusion ratios of all reservoir-cap combinations of biogas fields found there were calculated out, and then relationships of displacement pressure differences, biogas diffusion ratios, biogas reserves and unit reserves coefficient were investigated. According to the results, only the reservoir-cap combinations which had great displacement pressure differences were rich in biogas, and correspondingly, those with small displacement pressure differences could not be rich in biogas. On the other hand, reservoir-cap combinations with great diffusion ratios had small reserves and lower unit reserves coefficients, and those with small diffusion ratios always were high rich in biogas. Because the displacement pressure difference and biogas diffusion ratio represented quality of reservoir-cap combination, the relationships between the both parameters and biogas richment grades reflected controlling effect of reservoir-cap combination quality on distribution features and richment grades of biogas in Sanhu area.