压后关井期间压裂液黏度影响因素及预测模型研究

Investigation of Fracturing Fluid Viscosity Influencing Factor and Prediction Model during Shut-in Period after Hydraulic Fracturing

压裂液能否有效破胶是影响压裂效果的重要因素,破胶剂是实现压裂液顺利破胶的重要手段,现场主要依靠经验线性加破胶剂,通常出现压裂液破胶不彻底或过早破胶而影响压裂效果甚至导致压裂失败的现象。针对该问题,利用Arrhenius方程和黏时曲线建立了预测破胶对压裂液黏度影响的经验关系,结合黏度无因次预测模型,建立了综合考虑温度和破胶影响的压裂液黏度预测模型,利用该模型分析了压后停泵温度恢复和破胶剂浓度对压后关井期间压裂液黏度的影响。研究结果表明,停泵后温度恢复和破胶均会降低压裂液黏度;破胶对压裂液黏度的影响比温度更显著。该结果为确定关井时间和优化破胶剂加量提供了理论依据。

If the gel breaking of fracturing fluid was effective,it was an important factor affecting the effect of fracturing.Gel breaking down was an important meanings for smoothing gel breaking,in the oilfield the fracturing was based on empirical linear and gel breaker,incomplete gel breaking and earlier breaking would affect the effect of gel breaking or cause a failure of fracturing.In consideration of the problem,by using the Arrhenius equation and viscosity-time curve,an empirical relationship was established to predict the effect of breaking on fracturing fluid viscosity.In combination with a dimensionless viscosity forecasting model,a model was established for predicting the fracturing fluid viscosity considering the comprehensive effects of temperature and gel breaking.The model was used to analyze the impact of temperature recovery and breaker concentration on fracturing fluid viscosity during shut-in period after hydraulic fracturing.The results show that the temperature recovery and gel breaking would reduce the its viscosity and the influence of gel breaking on fracturing fluid viscosity is more obvious than that of temperature.The result provides a theoretical basis for determining the shut-in time and optimizing the breaker dosage.