Experimental study and analysis on a fluidic hammer-an innovative rotary-percussion drilling tool

Rotary-percussion drilling with mud as the energy carrier is a competitive method for the production of drill-holes. Fluidic hammer is a type of rotary-percussion drilling tool actuated by a fluidic oscillator based on the Coanda effect. By using a fluidic hammer, penetration rate can be significantly improved. With few movable or deformable parts, fluidic hammers are resistant to high temperatures, high pressure, corrosive and other extreme environments. Moreover, drilling through soft or inter-bedded formations need not stop to change bottom-hole assembly and can continue even though the fluidic hammer fail to operate. Given these advantages, fluidic hammers are convinced to be popular in the coming years and deserve being better known in the rotary-percussion drilling. In this work, a sequence of experimental investigations focused on the operability and effectiveness of a newly designed fluidic hammer under different sets of operational and physical parameters were performed. Some important impacting performance parameters in terms of impact velocity, impact frequency and impact force were obtained from the experimental results to evaluate the working performance of the fluidic hammer and the effect on bit life. An exponential function model was proposed to describe the piston motion. Comparison between the predicted values of the impact period obtained from the theoretical model and the experimental results reveals the rebound effect of the piston-hammer as it strikes the anvil or cylinder on the impact performance of the fluidic hammer. Furthermore, a field trial using a fluidic hammer was conducted in a horizontal directional well drilling to evaluate its effectiveness. An average improvement of 32.7% in penetration rate was recorded.