致密砂岩气藏成藏过程中的地质门限及其控气机理

Geologic thresholds and its gas-controlling function during forming process of tight sandstone gas reservoir

基于束缚水膜厚度不变的地质特征,通过对致密砂岩气藏储层的孔隙空间演化和流体变化规律分析,确定了致密砂岩气藏成藏过程中的3个地质门限,即天然气充注门限、天然气饱和门限和天然气终止门限,建立了相应的概念模型和计算模型,并就其对致密砂岩气藏的流体分布的影响和控制进行了系统的阐述。利用该模型对鄂尔多斯盆地上古生界致密砂岩气藏的预测结果表明,3个地质门限的对应深度分别为2 350m、2 850m和4 800m。经实际气藏剖面的正反检验表明,该模型对于预测致密砂岩气藏的流体分布具有较高准确性。

Based on the geological features of bound water film with fixed thickness,the change law and controlling factors of fluids in reservoirs during forming period of the tight sandstone gas reservoirs were analyzed.Three geologic thresholds in the forming process of tight sandstone gas reservoir,including gas injection threshold,gas saturation threshold and gas termination threshold,were established.The corresponding concept model and calculation model were set up and used to predict the tight sandstone gas reservoirs in the Upper Palaeozoic of Ordos Basin.The results indicated that the correspondence depths of three geologic thresholds were 2 350 m,2 850 m and 4 800 m respectively.The liquid distribution characteristics predicted by using above geologic model are in good agreement with those of actual reservoirs,which indicates that this model can be used to accurately predict the liquid distribution in the tight sandstone gas reservoir.