柴达木盆地三湖地区第四系生物气运聚成藏的定量研究

三湖地区第四系生物气在地下运聚的相态以游离气为主,约占生气量的70%以上,为该区直接形成游离相生物气藏提供了物质基础。生物气在地下的聚集成藏主要受控于同生圈闭,因此只有在下更新统K1同生背斜定型(距今1.35Ma)后排出和析出的游离气量才是可供聚集的有效排气量。压实水动力和浮力是游离气垂向运聚成藏的直接动力,可提供9.72×10⁸m³/km²的有效气量;下渗水动力是含气水流侧向运移的动力,可提供1.08×10⁸m³/km²的有效气量。根据运聚动力、运聚数量和聚集样式的分析,三湖地区第四系生物气可概括为"自生自储、以近源垂向运聚为主、受同生圈闭控制"的成藏模式。在此基础上预测该区第四系生物气的地质资源量为11210×10⁸m³,三级储量为5604×10⁸m³。

Quantitative research on biogas migration-accumulation and pool-forming in the Quaternary of Sanhu area in Qaidam Basin

The migration and accumulation phase of biogas in the Quaternary of Sanhu area in Qaidam Basin is mainly free-phase gas accounted for more than 70% in total, which can provide the material base for the accumulation of free-phase biogas in this area. Bio-gas pools underground are mostly controlled by contemporaneous trap. So, the free-phase gas expelled and released after shaping of the syn-sedimentary anticline in the Lower Pleistocene(1. 35 Ma before present)is the effective expulsion gas quantity. The compac-tion hydrodynamic and buoyancy are the direct motivation for the vertical movement of the free-phase gas and can provide 9. 72× 10~8m~3/km~2 of effective expulsion gas quantity. The downward infiltration hydrodynamic is the impetus of lateral migration of the contained gas current and can offer 1. 08×10~8m~3/km~2 of effective expulsion gas quantity. According to the dynamic,quantity and style features of free-phase gas migration and accumulation, the Quaternary gas accumulation model can be summarized as "self-gen-eration and self-accumulation, dominated by vertical migration-accumulation near the source and controlled by the contemporaneous trap". The geologic resources of biogas count up 11 210×10~8m~3 and the possible reserves are 560×10~8m~3 in the Quaternary of San-hu area.