砂岩气藏充注含气饱和度实验研究

针对低渗致密砂岩储层充注含气饱和度难以准确测试技术难题，综合考虑储层展布及物性差异特征、充注动力、地温条件、盖层封闭等要素，建立一套全序列砂岩储层充注含气饱和度测试实验方法，分别对渗透率为0.034×10^-3μm²、0.075×10^-3μm²、0.244×10^-3μm²、0.505×10^-3μm²、0.683×10^-3μm²、1.12×10^-3μm²、1.47×10^-3μm²、4.77×10^-3μm²、10.7×10^-3μm²、38.1×10^-3μm²、49.1×10^-3μm²、99.4×10^-3μm²、126×10^-3μm²的砂岩储层，开展了气源压力为0.1MPa、0.2MPa、0.3MPa、0.5MPa、0.7MPa、0.9MPa、1.0MPa、1.2MPa、1.5MPa、1.8MPa、2.0MPa、2.5MPa、2.8MPa、3.0MPa、3.5MPa、4.0MPa、4.5MPa、5.0MPa、5.5MPa、6.0MPa、7.0MPa、8.0MPa、10.0MPa、15.0MPa、20.0MPa、25.0MPa、30.0MPa下逐级增压充注实验，记录了充注过程中各渗透率储层孔隙压力变化特征，在此基础上，采用充注实验与核磁共振实验结合的方法，对充注过程中含气饱和度变化进行了量化评价。研究结果表明：①低渗致密储层充注时具有高于门限压力进气，源、储压力平衡缓慢以及高压聚气三大特征，进气门限压力与储层渗透率关系密切，建立了门限压力与渗透率关系图版；②认识了含气饱和度（S_g）、地层压力（P）与储层渗透率（K）变化规律，拟合了含气饱和度经验计算公式，以鄂尔多斯盆地苏里格气田为例，通过实验测试、密闭取心分析与经验公式计算结果对比，建立了含气饱和度与储层渗透率关系图版，为低渗致密砂岩气藏储层含气性评价提供指导；③以取心井为基础，根据含气饱和度、储层渗透率、孔隙度、厚度等参数，建立不同渗透率储层储量辟分方法，为储量分类评价提供了依据。

The experimental research of filling gas saturation in sandstone gas reservoir

Aimed at the problem of the determination of charging gas saturation of low permeability in tight gas reservoir,a set of testing method of full sequence charging gas saturation of sandstone reservoir is established,taking into account the reservoir distribution,reservoir petrophysical property difference,driving force,geothermal condition and cap sealing capacity.The pressurized charging gas testing has been carried out on the sandstone with permeability of 0.034×10^-3μm² ,0.075×10^-3μm²,0.244×10^-3μm²,0.505×10^-3μm²,0.683×10^-3μm²,1.12×10^-3μm²,1.47×10^-3μm²,4.77×10^-3μm²,10.7×10^-3μm²,38.1×10^-3μm²,49.1×10^-3μm²,99.4×10^-3μm²,and 126×10^-3μm²,and the gas source pressure are 0.1MPa,0.2MPa,0.3MPa,0.5MPa,0.7MPa,0.9MPa,1.0MPa,1.2MPa,1.5MPa,1.8MPa,2.0MPa,2.5MPa,2.8MPa,3.0MPa,3.5MPa,4.0MPa,4.5MPa,5.0MPa,5.5MPa,6.0MPa,7.0MPa,8.0MPa,10.0MPa,15.0MPa,20.0MPa,25.0MPa,and 30.0MPa.In the charging gas testing,the varying law of pore pressure is recorded and the gas saturation is quantitatively evaluated by the nuclear magnetic resonance.The research shows that:①Higher intake gas pressure than the threshold pressure,slow balance progress of gas source pressure and reservoir pressure and gas gathering in high pressure are the three characteristics of the low permeability sandstone tight gas reservoir in the gas charging testing.The intake gas threshold pressure is related to the reservoir permeability closely and their relation chart is established.②The varying law of gas saturation with pore pressure and reservoir permeability is got and the gas saturation empirical formula is established by fitting the testing data.Taking the Sulige gas reservoir in the Ordos Basin as an example,the empirical formula of gas saturation is verified by lab testing and confined coring analysis and the relation chart of gas saturation and permeability is established,which can guide the gas content evaluation in the low permeability tight sandstone gas reservoir.③The reserve splitting method of different permeability reservoir is established,which takes into account gas saturation,reservoir permeability,porosity and thick,providing a basis for reserve classification evaluation.