Friction Reducers for Slick Water:Performance Evaluation and Friction Prediction

Deficiencies exist in empirically predicting the friction reducing efficiency of slick water fracturing fluids in field operation, yet the experimental methods presently in use for evaluating the performance of friction reducers are only focused on the performance comparison and product optimization, while the illustration of how to apply the test results to field operation is rarely seen in literatures. To resolve this problem, a laboratory loop-line friction measurement system has been established. According to the Prandtl-Karman law, the diameters of three straight pipes used in the system were determined to be 10.46 mm, 7.59 mm and 5.86 mm using turbulent flow rate of clear water. For any one of the pipe diameters, the frictional pressure drops of five different concentrations of DR-800 (a friction reducer) water solutions were tested at a certain flow rate. For the 0.07% and 0.10% DR-800 solutions, the test pressure drops were converted into frictional coefficients, and then corresponded with the Reynolds numbers calculated which took into account viscosity. In this way the frictional coefficients can be satisfactorily fitted with Virk asymptote, and the excellent performance of the DR-800 was proven. After quantitatively measuring the friction reducing performance, using friction-velocity method (a submethod of the so-called friction amplification method), the ratios of friction reduction and velocities-under-friction obtained from the experiments can be regressed into a mathematical expression that can be used to work out the rate of friction reduction corresponding to a specific velocity-under-friction. Using this expression, a comparatively affirmative rate of friction reduction under a work condition can be determined through iteration. The calculation has better precision than empirical prediction, and the laboratory study method is instructive to the field application of friction reducers.