Fluidic DTH hammer with backward-impact-damping design for hard rock drilling

Abstract

Hard rock drilling is increasingly important due to progress in both the use of geothermal heat as a new energy source and the development of new unconventional gas fields. The DTH hammer drilling method is generally considered one of the best approaches for drilling hard rocks. A fluidic DTH hammer with backward-impact-damping design for hard rock drilling was proposed in the study. Striking features of this DTH hammer tool include extended life expectancy and capability to withstand drilling fluids solids content. A sequence of numerical and experimental investigations were performed on the newly designed fluidic DTH hammer. It is observed that the backward-impact-damping design is effective in protecting the fluidic oscillator from damage. Although the backward-impact-damping design may cause a decrease in the single-impact energy, the increased impact frequency can offset the aforementioned disadvantage to a certain extent. The paper brings attention to several interesting aspects of the fluidic DTH hammer. The accumulated data provide useful information to develop this type of a DTH hammer and facilitate its popularization and application in hard rock drilling.