Study On The Evaluation Method Of Temperature Stabilizer For Fracturing Fluid

The thesis designed the standardized evaluation method for temperature stabilizer of fracturing fluid,which is the basement for proper choice and application of temperature stabilizer.The representation and characterization parameters for thermal stability of fracturing fluid were analyzed,and the action mechanism of temperature stabilizer was classified.And the paper also analyzed the shortcomings of the evaluation methods of the temperature stabilizer of fracturing fluid in the oil field.Based on that,this paper designed a new evaluation method for temperature stabilizer of fracturing fluid.And the main contents and conclusions are listed below:Firstly,the new evaluation method for temperature stabilizer of fracturing fluid took the minimum requirements of viscosity and the time of fracturing construction into account in the meantime.It was proposed the effectiveness of temperature stabilizer should be characterized by measuring the difference ofΔT for fracturing fluid before and after adding the temperature stabilizer.where T_max（η₀,t₀）is the maximum temperature of the fracturing fluid ensuring the fracturing operation time and the minimum required viscosity.Secondly,the HPG fracturing fluid and temperature stabilizer S-1 used in Shengli oilfield was selected as an example to illustrate the evaluation method.The evaluation procedures are achieved by gradually searching the T_max(η_0,t₀)through viscosity time-viscosity temperature curve of fracturing fluid.Because the maximum temperature of the fracturing fluid only ensuring the minimum required viscosity T_max is easily determined by the viscosity temperature curve of fracturing fluid and also larger than T_max(η_0,t₀),the searching processes can be shortened using the binary search method and setting T_max as the upper limit temperature.And then,the temperature stabilizer effectiveness is characterized by improvement value of applicable temperatureΔT,which is calculated by the difference of T_max(η_0,t₀)for fracturing fluid before and after adding the temperature stabilizer.The experimental results confirmed the rationality of the evaluation method.Thirdly,The influence of powder ratio,pHs,concentration of crosslinker and temperature stabilizer on the heat and shear resistance of fracturing fluid was studied by using the new method of evaluating the temperature stabilizer of fracturing fluid.The effects of different factors on the heat and shear resistance of fracturing fluid were analyzed by comparing the different powder ratio,different pHs,different concentration of crosslinking agent and different temperature stabilizer.In a certain range,the powder ratio,pH value,crosslinking ratio and temperature stabilizer have a certain effect on the heat and shear resistance of fracturing fluid.The numeric order of optimum temperature for the two temperature stabilizers wasΔT_max<ΔT,which proved that the designed evaluation method was superior to the existing evaluation method.Forthly,The effect of powder ratio,pH value,crosslinking ratio and temperature stabilizer on the heat and shear resistance of fracturing fluid system could get a conclusion that the trends in T_max and T_max(η_0,t₀)are similar.The method of measuring T_max(η_0,t₀)had a theoretical basis,because it was a combination of two methods for measuring the temperature resistance and heat and shear resistance of water-based fracturing fluid performance evaluation method.In a word,it was feasible to characterize the heat and shear resistance of fracturing fluid with T_max(η_0,t₀).