Design and optimization of sealed sampling bit in underground coal mine

The existing sealed sampling technology has some problems such as severe pollution of drilling fluid, small sampling amount and low sampling success rate. In order to solve these problems, the water path structure and sampling part of conventional bottom spray PDC sampling bit are optimized. The inclined water path structure is combined with three kinds of small bits, and the flow field of the bit and the force at the bottom of the hole are obtained through simulation, the simulation results show that the optimal design is feasible. A sealed pressure-retaining sampling test was carried out in Chengjiao Coal Mine of Henan Zhenglong Coal Industry Co., Ltd., five sampling times were carried out, and four of which were successful. The maximum sampling amount was 1 024 g, and the minimum was 475 g, the normal sampling rate was over 70%, the amount of sampling was about one time higher than that of conventional bottom spray sampling bit.