Issue34

J. He et alii, Frattura ed Integrità Strutturale, 34 (2015) 564-573; DOI: 10.3221/IGF-ESIS.34.62 571 5 5.48 10   while the particle size in drilling muds is 75  m. The erosion rate difference is 22.4% when particle size is ranging from 20  m to 75  m. Thus the effect of particle size on anti-erosion property should be drawn enough attention. Suggestions can be provided that the particle size of drilling mud should be less than 20  m, which means the low solids clay-free mud system is preferentially selected while in drilling process. Otherwise, the mud purification system is proposed due to the existence of large particles in drilling muds while drilling directional wells or vertical wells. Effects of Solid Content on Anti-erosion Property As shown is Fig. 6, the anti-erosion property of a fluidic amplifier is affected by the solid content of drilling muds. It can be concluded that the erosion rate of a fluidic amplifier is almost exponentially varies with the solid content of drilling muds. While the solid content of drilling muds exceeds 8%, the maximum erosion rate of the fluidic amplifier is more than 4 1.12 10   . Otherwise the minimum erosion rate of the fluidic amplifier is less than 4 4.73 10   while the solid content of drilling muds is 2%. The actual simulation results are slightly different with the fitted erosion rate, and the deviation between simulation results and fitted erosion rate is less than 4%, which is acceptable in real operation of hydraulic hammers with a fluidic amplifier. The erosion of a fluidic amplifier is lower, the longer service life of the hydraulic hammer will be. In order to improve the service life time of the fluidic amplifier, the solid content of drilling mud system should be controlled below 8%, thus the mud purification system and low solid clay-free mud system are still suggested in horizontal directional or vertical well drilling. Figure 6 : Erosion rate of drilling muds on a fluidic amplifier varies with the solid content of drilling muds. Figure 7 : The moving trajectory of solid particles colored by velocity magnitude.