超深层碳酸盐岩地层水启动压力梯度研究

Study on Formation Water Threshold Pressure Gradient of Ultra-deep Carbonate Reservoir

为厘清地层水启动压力梯度随地层水黏度和岩石渗透率的变化规律,选取四川盆地飞仙关组超深层碳酸盐岩标准岩心,开展了不同地层水黏度条件下的启动压力梯度实验测试,得到了地层水启动压力梯度随地层水黏度的变化规律,建立了综合考虑岩石物性和流体性质的地层水启动压力梯度预测模型。根据普光气田主体气藏气井测井解释成果,采用新建模型预测了气藏不同类型储层在不同地层水黏度条件下的启动压力梯度。结果表明:地层水启动压力梯度随渗透率降低而增大,在渗透率相对较低时,地层水启动压力梯度随渗透率降低急剧增大;地层水启动压力梯度随地层水黏度的增大而增大,黏度越大,启动压力梯度随渗透率降低而增大得越快。新建模型综合考虑了岩石物性和地层水性质对地层水启动压力梯度的影响,适应性较强。普光气田Ⅱ、Ⅲ类储层地层水启动压力梯度最大可达0.24 MPa/m。

The experimental test of threshold pressure gradient of formation water of different viscosity is carried out based on the standard cores of ultra deep carbonate rock in Feixianguan Formation of Sichuan Basin.The variation law of threshold pressure gradient of formation water with formation water viscosity is determined,and the prediction model of threshold pressure gradient of formation water considering physical properties of rock and properties of fluid is established.According to the well logging interpretation results of the main gas reservoir in Puguang gas field,the threshold pressure gradients of formation water with different viscosity in different types of reservoirs are predicted using the established model.The results show that:the threshold pressure gradient of formation water increases with the decrease of formation permeability;when the permeability is relatively low,the threshold pressure gradient of formation water increases sharply with the decrease of permeability.The threshold pressure gradient of formation water increases with the increase of formation water viscosity,and the higher the viscosity is,the faster the threshold pressure gradient increases with the decrease of permeability.The new model comprehensively considers the influences of rock physical properties and formation water properties on the threshold pressure gradient of formation water,and has strong adaptability.The maximum threshold pressure gradient of formation water in class II and class III reservoirs of Puguang gas field can reach 0.24 MPa/m.