Optimized design and surface additive technology of PDC bit for hard rock directional drilling

Directional long drilling is the main technical means of gas and water hazard control in coal mines, and the performance of PDC directional bit is an important factor which affects the drilling efficiency in hard rock. In view of frequent tripping and low that caused by the broken PDC bit body and PDC tooth collapse in the construction of directional long drilling in the roof and floor of coal seams, the principle of equal cutting teeth distribution is used to optimize the blade teeth distribution to reduce the impact damage of the cutter. Through the simulated analysis of fluid mechanics, the hydraulic parameters of the bit were optimized to ensure that the rock debris was discharged timely from the bottom of the hole to prevent the cutter from being damaged prematurely due to repeated cutting. Large-size abnormal teeth without cobalt were selected to improve the wear resistance and impact resistance of the cutters. The surface additive manufacturing technology of steel body bit was studied. By optimizing PTA additive manufacturing process parameters, the bit body with an abrasion resistance of a matrix bit body and the strength and toughness of a steel body was developed. The field test of the newly developed PDC directional drill bit was carried out in the water exploration and discharge hole of the floor in the north area of Guqiao Coal Mine in Huainan. The results show that when drilling in dense and hard limestone formations, the life of the two drill bits reaches 827 m and 810 m, respectively, which is greatly improved compared with the previous ø120 mm directional drill bit with an average life of 300 m. The time of auxiliary operations such as drilling up and down is reduced, and the construction efficiency is improved. The goal of increasing the speed and efficiency of directional long drilling in the hard layer is achieved. This study provides a new solution for the design and manufacturing process development of PDC bits for hard rock directional long drilling.