Abstract: To address the problem of premature failure of PDC drill bit due to low rock-breaking efficiency and lateral vibrations and swirls of drill string caused by lateral force surge when drilling in soft and hard interbedded layer,a PDC drill bit with directional double-tooth structure was designed,and the effects of the directional double-tooth structure with different tooth arrangement parameters on rock-breaking efficiency and local lateral force balance were investigated by the finite element simulation of double-tooth cutting. The results show that the directional double-tooth structure can effectively improve the rock-breaking efficiency,the double-tooth spacing has less effect on the mechanical specific power,compared with the single-tooth cutting,the mechanical specific power is reduced by about 5.60%-6.50%; the double-tooth clamping angle can significantly affect the mechanical specific power,when the double-tooth clamping angle is 160 °,compared with the single-tooth cutting,the mechanical specific power is reduced by about 96.36%-113.82%; under the same side turning angle,the lateral force of the double-tooth clamping angle tooth arrangement is reduced by about 33.40%-74.20% compared with that of the single-tooth cutting,which can effectively improve the local lateral force balance of the drill bit in the transitional formation and directional drilling,and thus improve the overall force balance effect of the drill bit. This study can provide a reference and basis for the optimized design of the tooth arrangement of the PDC drill bit.

Key words: directional double-tooth, PDC drill bit, mechanical specific power, lateral force balance, soft and hard interbedded layer, deep formation, ultra-deep formation