Optimization Of Key Parameters For PDC Bit's Design

In view of the research of PDC key parameter relative lag, little certain regularity and the designs often depending on experience or analogy to others, the author has studied a series of key parameters that impact on PDC drill bit through the laboratory experiment and the numerical simulation, such as the shape of crown, degree of back rake angle, the cogging size, the tooth density, the degree of inner cone, the height of inner / outer cone and the position of crown. The results of study show that: (1) The cogging size is in inverse proportion to formation hardness on broken rock efficiency. When the kd is less than 3.48, and the diameter of cogging is19.05mm, It should obtain higher drilling rate. Also the drilling rate will be higher when kd is 3.48-5.78, and the diameter is 16.10mm. (2) The drilling rate can increase if the back rake angle is between 10°and 15°when kd is less than 3.48, Also it will be higher when the back rake angle is 15°and 20°and kd is 3.48-5.78. (3) The cogging density is in inverse proportion to the drilling speed.(4) Higher drilling speed can be got through the"straight line - arc - straight line"section when kd is less than 3.5.And it also can be got through"straight line-arc-arc"section when kd is between 3.48-4.6. (5) The design of deep inner cone can improve bit stability and cogging life. When the degree of inner cone changes in 90°-160°, the force of crown tends to evenly under the function of drill pressure with the degree of inner cone increasing, also the torque is not obvious to the force of the crown. (6) The design of high outer cone may enhance drill rate effectively. The stress of outer cone increases gradually with the angle longer and longer, simultaneity the bit pressure and the torque are obvious to the outer cone when the outer cone changes from 25°to 45°. (7)When the ratio of crown radius and bit radius is 0.64,the centralized phenomenon of stress of crown is obviously reduced. The research results have certain directive significance to individualized design of PDC bit .