The friction loop effect of the drag reducer is mainly shown as that the pressure drop of the friction loop of the fluid flow decreases and the flow speed increases after adding the drag reducer, which can be measured by the friction loop rate and transport increase rate. But the friction loop rate is generally used to describe it at home and abroad. The calculation formula of the friction loop rate is as follows:
When testing the friction loop rate, firstly put the evaluation fluid in the flowback tank, and wait until its temperature is constant at 20 degrees Celsius, then drive it into the pressure buffer tank with gear pump, pressurize the buffer tank with nitrogen gas cylinder pressure to the preset test pressure, after the pressure being stable, open the corresponding valve, make the evaluation fluid flow back to the flowback tank, and measure the pressure drop of the friction loop and flow in the process. Repeat the above process until the two measurements agree. Then, the diesel oil is pumped into the dilution stirring tank with gear pump, and add the previously prepared friction reducer solution. The diesel oil is mixed evenly with the stirrer, and then it flows naturally into the pressure buffer tank (the nitrogen in the pressure buffer tank is emptied). After all flow is completed, pressurize again and being stable, the then pressure drop of the friction loop and flow rate are measured.
It was found that the friction loop rate varied with the concentration of the drag reducer. The friction loop rate increases with the increase of the concentration of the drag reducer, but the friction loop rate does not have a linear relationship with the concentration of the drag reducer. When the concentration is relatively low, the friction loop rate increases comparatively quickly with the increase amplitude of the concentration, while when the concentration is relatively high, the friction loop rate increases comparatively slowly with the increase amplitude of the concentration. When the concentration increases to a certain amount, the friction loop rate does not increase with the increase of the concentration, but tends to be a fixed value.