Mechanism Study On The Bottomhole Pressure Reduction By Drilling Fluid Shunt On Bit

Penetration rate decreased obviously with the depth increased while drilling deep well and ultra deep well. Bottom hole pressure is one of the main factors affecting the drilling speed, cuttings can't be cleared in time, causing duplication of broken rock, caused the rapid decline in ROP.In view of the basic principles of influence on ROP , reducing the bottom hole pressure by fluid shunt on bit can significantly reduce the"chip hold down effect"and increase drilling speed.Based on theoretical analysis, chang the structural parameters and hydraulic parameters of nozzle and bit flow structure to simulate the bottom flow field .Analyse of bottom hole confining pressure, flow structure of the bit , nozzle and pipe diameter, shunt flow ratio, the nozzle position, the gap of bit and hole ,and other factors on the effect of reducing the bottom hole pressure by fluid shunt, dimensionless pressure drop can reach 0.26 greatly. Attached to the wall bistable jet element is applicated to coordinate pulse jet, dimensionless pressure drop can reach 0.5,the effect of pressure drop is better than continuous shunt. Based on the simulation of the drill bit and wellbore model experimenta tools to experiment, and analyse confining pressure, shunt flow ratio, the position of nozzle , the gap of bit and hole, and other factors on the effect of reducing bottom hole pressure by fluid shunt, dimensionless pressure drop can reach 0.35.The conclusion is consistent with the numerical results. Finally, using PDC bit design software, combined with numerical simulations and laboratory conclusion to design the bit and hydraulic structure, and lay the foundation for the development of the new and high efficiency drill bit.