The efficiency of rock breaking when drilling wells by the pellet impact method at different angles of wellbore inclination

摘要

Introduction. This paper considers the pellet impact drilling method which implies rock destruction by metal pellets impacting the rock. A. B. Uvakov carried out successful research on directional drilling by the pellet impact method that showed a positive result. However, little attention was paid to bench laboratory studies. Moreover, there is no information on the efficiency of pellet impact drilling at various angles of wellbore inclination. The research objective is to analyze the efficiency of rock breaking in the process of well drilling by the pellet impact method at various angles of wellbore inclination to vertical.Methods of research. The author has designed and manufactured a laboratory bench to conduct the research. The laboratory bench design provides drilling mud closed circulation and cuttings removal by gravity settling. A PMMA tube placed inside a metal glass imitate wellbore walls. Samples of ceramic tiles imitating rocks were used in the experiments. The volume of rock drilled out per unit of time was determined at various pellet portion masses and angles of wellbore inclination to vertical. Results. The present research was the first to find the dependency between the angle of wellbore inclination to vertical and rock breaking efficiency during pellet impact drilling. Four sets of experiments were carried out at different zenith angles: 0°, 30°, 60°, and 90°. It has been found that pellet impact drilling is possible at different angles of wellbore inclination to vertical up to 90° (horizontal wellbore); drilling efficiency increases with the zenith angle. The cylindrical shape of the wellbore is retained. Summary. The results obtained expand the potential scope of the pellet impact drilling method and improve drilling efficiency forecast when constructing directional wells.