南堡凹陷沙三段致密砂岩气成藏条件

在对烃源岩和储层基本特征分析的基础上，采用生烃潜力法恢复了烃源岩的排烃历史，并从数值模拟的角度研究了储层孔隙度的演化历史。结果表明，渤海湾盆地南堡凹陷沙河街组三段具有良好的致密砂岩气成藏地质条件：中等-好的供气源岩和广泛分布的致密储层，烃源岩与致密储层紧密相邻，天然气成藏时间和储层致密时间配置较好。烃源岩的排气高峰时间是在馆陶期到明化镇早期，储层致密的时间是馆陶末期到明化镇早期。在生烃增压造成的气体膨胀力作用之下，天然气可近源聚集在紧邻烃源岩分布的致密透镜状岩性砂体中，形成连续型致密砂岩气藏。

Accumulation conditions of tight sand gas in the 3 rd member of the Shahejie Formation in Nanpu Sag,Bohai Bay Basin

Based on analyses of the source rocks and reservoirs in the Es³ (the 3^rd member of Shahejie Fm), the hydrocarbon expulsion history was restored with the hydrocarbon generation potential method, and evolution history of reservoir porosity was established through numerical modeling.The results show that accumulation conditions of tight sand gas in the Es³ in the Nanpu Sag of the Bohai Bay Basin are pretty good: fair-good source rocks and widespread reservoirs were closely connected with each other, and the timing of gas accumulation and reservoir tightening was favorable.The peak gas expulsion occurred from the Guantao to early Minghuazhen, while the reservoir tightening was from the late Guantao to early Minghuazhen.These gases might accumulate in the lenticular sand body near the source rocks under the force of gas expansion, forming continuous tight sand gas reservoirs.