考虑流变特性改变的水力压裂管内摩阻计算模型研究

Research on Computation Model of Friction in the Oil Tube during Hydrofracture with Consideration of Rheology Change

水力压裂管内摩阻的准确计算是确定井底压力和地层破裂压力的关键。压裂过程中由于压裂液与地层之间的热交换,压裂液的流动温度会发生明显变化;而温度的改变会影响压裂液的流变特性,使得不同深度处单位长度流体流动摩阻发生改变。通过建立油管注液过程管内流体温度分布数学模型,得到了不同油管注入排量下管内液体温度沿井深的分布。结合温度对压裂液流动特性的影响实验,考虑压裂液流性指数和稠度系数沿井深的变化,建立了压裂过程中管内流动摩阻的分段计算模型。通过与现场实测摩阻数据对比,模型与传统不考虑压裂液流变特性改变的摩阻力计算模型相比更为符合工程实际。

Accurate calculation of flowage friction in the oil tube is the key to determine the value of bottom pressure and formation breakdown pressure. Because of the heat exchange between fracturing fluid and formation, the flowing temperature of fracturing fluid has significantly changed. Besides, temperature＇ s change has an impact on flow behaviour of fracturing fluid, which makes flowage friction of unit length fluid in different well depth une- qual. The distribution of fluid temperature in the oil tube along the depth direction under the condition of different tubing injected capacity can be obtained through establishment and solution of mathematical model of wellbore tem- perature distribution in the context. Experiment that researchs the relationship between the behaviour of fracturing fluid and temperature is also conducted. So, the distribution of liquidity index and consistency coefficient of fractu- ring fluid along the depth direction can be obtained. Piecewise computation model of flowage friction in the oil tube is established at last. Compared with the traditional computation model of flowage friction that isn＇ t taken the change of liquidity index and consistency coefficient into consideration, the piecewise model is more coincided with measured data in well site.