Hot-water coring system with positive displacement motor

In this study, a new coring system is designed that uses a positive displacement motor (PDM) connected to a core barrel and drill bit in combination with a hot-water drilling (HWD) system. The surface equipment and water hose are shared and the hot-water drill nozzle is replaced by the corer when a borehole is made by HWD. The hot water is then utilized to drive the PDM corer. In this paper, the concept of the PDM coring system is presented, along with a novel self-adaptable anti-torque device that can automatically adjust the diameter to adapt to an irregular borehole. The required force-energy parameters of the PDM are theoretically estimated. A PDM coring system is designed and assembled, and the feasibility of the concept is tested in the laboratory. The results indicate that it is more conducive to perform the coring at a lower temperature of water. At a temperature of 5° C, a double-walled core-barrel works adequately to produce ice cores with a maximum diameter of 73 mm and an inner barrel diameter of 79mm at a water flow rate of 96 L/min.