考虑稠油非牛顿性质的蒸汽吞吐产能预测模型

A productivity prediction model for cyclic steam stimulation in consideration of non-Newtonian characteristics of heavy oil

与常规油不同,当达到某特定温度时,稠油呈现牛顿流体状态,而在该温度值以下时,稠油呈现非牛顿流体状态,即存在启动压力梯度。经典的解析模型将蒸汽吞吐分为热区与冷区2个部分,热区温度为蒸汽温度,冷区温度为原始地层温度。然而在实际过程中,热区到冷区的温度是一个非等温的渐变过程,不会存在热区与冷区的边界处的突变现象。而且在生产过程中,稠油在不同区域呈现牛顿流体与非牛顿流体2种状态,不同区域的稠油渗流方程不同。针对这种情况,基于Marx-Langenheim方程,对蒸汽吞吐的解析模型进行了改进。在注入阶段,考虑了热区非等温分布的特征;在生产阶段,考虑了稠油牛顿流体区与非牛顿流体区的渗流耦合。模型应用结果表明,该模型更加接近实际生产情况,有较好的应用价值。

Unlike conventional oil,heavy oil exhibits Newtonian fluid state when it reaches a specified temperature.Specifically,heavy oil shows non-Newtonian fluid state at a temperature below the specified value,i.e.,a threshold pressure gradient occurs.In a classical analytical model,the reservoir for cyclic steam stimulation is divided into hot zone and cold zone;the temperature of hot zone is steam temperature while that of cold zone is initial formation temperature.However,in practice,temperature transition from hot zone to cold zone is a non-isothermal gradual change process,and no abrupt change will occur at the boundary between hot zone and cold zone.Moreover,during production,heavy oil presents two states in different zones,i.e.,Newtonian fluid and non-Newtonian fluid;correspondingly,heavy oil flow equations are also different.In light of the two points above,the analytical model of cyclic steam stimulation was modified on the basis of Marx-Langenheim equations.Considerations included non-isothermal distribution characteristics of hot zone during injection stage and flow coupling of heavy oil in Newtonian fluid zone and non-Newtonian fluid zone during production stage.The results of the model application shows that this model is more close to actual production situation and has better applicability.