Study On The Abrasion Of Coiled Tubing Annulus Fracturing And Reverse Circulation Sand Washing

With the application of increasing coiled tubing fracturing and sand washing in recent years,the wear of coiled tubing caused by particles has become one of its main failure forms.Aiming at the wear caused by high-volume concentration particles on the wall of the coiled tubing in the process of annulus fracturing and reverse circulation sand washing,the Euler-Euler two-phase flow model is used to numerically calculate the wear of the coiled tubing annulus fracturing and reverse circulation sand washing process by selecting a combination of Archard abrasion model with E/CRC erosion model and compiling the corresponding user-defined functions interface program in Fluent,and explores the wear mechanism of high volume concentration particle flow and the impact of some key parameters on wear.The results show that,whether in the process of coiled tubing annulus fracturing or reverse circulation sand washing,the impact angle of particles on the wall is almost all less than 5°,which indicates that the wear mechanism at high volume concentration particle is mainly abrasion,supplemented by erosion.In the process of coiled tubing annulus fracturing,the maximum wear rate of the coiled tubing under sinusoidal buckling is larger than that without buckling deformation.The larger the buckling amplitude,the greater the maximum wear rate,and the location of the maximum wear rate occurs near the upper wall at the buckling valley of the coiled tubing.When the displacement of fracturing fluid increases from 1m³/min to 8m³/min,the maximum wear rate increases from 2.00×10^-9m/s to 1.07×10^-6m/s,and the thickness loss of the coiled tubing wall from 0.0185mm increased to 1.2346mm after pumping 100 tons of sand.In the process of coiled tubing reverse circulation washing,the wear mainly occurred in the outer curvature radius of coiled tubing inner wall,and the maximum wear rate occurs near the inlet section regardless of the flow velocity,particle concentration,particle size and fluid properties.The larger the displacement,the more serious the wear,when the displacement increases from 200L/min to 600L/min,the maximum wear rate increases from 6.06×10^-11m/s to 2.15×10^-10m/s.The greater the viscosity of the fluid,the less the wear caused.The maximum wear rate caused by the use of 0.5%stock solution is only 53%of the use of water at 600 L/min displacement.The research results of this paper can provide the theoretical support for reducing wear and predicting the life of coiled tubing.