Transportation of cuttings through drill rods during reverse-circulation reaming

Abstract

Researchers have proposed that reverse-circulation reaming can improve the efficiency of the transportation of cuttings during horizontal directional drilling. This research aims to establish a method to calculate the critical flow velocity of the cutting–mud mixture and friction loss in the transportation of the mixture during the reverse-circulation reaming process. A medium-scale reverse-circulation reaming system was established to determine the practicability of the proposed calculation method. The rotational speed of the drill rod influenced the friction loss in the transportation of the cutting–mud mixture but had little effect on the transportation mode of the cuttings. When the drill rod remained stationary, the minimum flow velocity of the mixture was a good estimate of the critical flow velocity of the mixture. When the flow velocity of the mixture in the drill rod was lower than the critical flow velocity of the mixture, the cuttings were transported via bed-load transportation, and the rotation of the drill rod reduced the friction loss in the transportation of the mixture. The results suggest that the proposed calculation method is suitable to determine the critical design parameters of the reverse-circulation reaming process.