Design and Experiments of Directional Core Drilling Tool

In the coring process of ocean drilling, conventional vertical holes face many difficulties, such as the high cost of single holes and limited acquisition of geological information, which cannot meet the demand for fine delineation of strata around drill holes. For this reason, based on wire-line coring and directional drilling technology, a continuous core tool for directional drilling has been designed, which can efficiently and accurately obtain cores in seabed strata and improve perceptions of target geological bodies. In this paper, the structure and working principle of a directional coring drilling tool (DCDT) were introduced in detail, and the ultimate deflecting capacity of a hollow single bend sub (HSBS) and the power demand of a positive displacement motor (PDM) were calculated. Then, an experiment platform was established to test the performance of the DCDT prototype. The test results showed that a total core length of 5.15 m was obtained among hybrid drilling processes, and the maximum core recovery rate was 91.67%. In slide drilling processes, the core recovery rate was only 55–60%, and the calculated build-up rate reached 7.5°/30 m. Through simulation and experiments, the key components of DCDTs were verified. This research will promote the optimization of DCDTs and accelerate engineering applications.