Drag Reducing Performance Comparison of Surfactant and PAM Based Drag Reducer

摘要

Slick-water with excellent performance on drag reduction(DR)is the preferred fracturing fluid for shale gas fracturing.In order to select appropriate slick-water for hydraulic fracturing under varying formations and construction conditions,this experiment focused on measuring the DR performance of different kinds of slick-water.Using polymer and viscoelastic surfactant as DRA,the frictions of slick-water were measured by friction tester;DR rate was calculated by using friction of fresh water as blank.The principle is to test the pressure drop between inlet and outlet of pipeline when the fluid flows through a certain tube under a range of flow rates.Specifically,in this work,a kind of modified acrylamide(MPAM)and cetyltrimethylammonium bromide/sodium salicylate(CTAB/NaSal)were adopted as DRA.In comparison,frictions and DR of MPAM solutions are quite different from those of surfactant solutions.The frictions of water and MPAM solutions increase with the increase of flow rate,and the relationship of friction and flow rate is approximately linear.For MPAM solution,DR is related to the concentration of MPAM,high concentration result in high DR rate.But for surfactant based viscoelastic fluid,frictions are very low;with the increasing of flow rate,the friction increases greatly.DR of viscoelastic fluids is related to the modulus of the fluid,the better the viscoelastic fluid conforms to the Maxwell model,the higher DR rate can be obtained,and this is proved by rheological experiments.Under high flow rate,viscoelastic fluid becomes thinner due to shearing and DR decrease substantial as a result.From the experiments,polymer solution shows good shear resistance performance,DR increase with the increase of flow rate,but in the application of slick-water fracturing,a large amount of hard-to-degrade polyacrylamide entering the formation may cause pollution to reservoirs,while degradable surfactant-based viscoelastic fluids were poor shear resistance.As a result,neither MPAM nor surfactant-based viscoelastic fluid are suitable for all reservoirs,it is necessary to select a suitable fluid according to pump speed,environment protecting and other factors in applications.