AN APPLICABLE METHOD FOR ESTIMATION OF FORMATION DRILLING STRENGTH AND BIT WEAR

Based upon the theory of rock-breaking mechanism of one tooth of roller bit and the theory of force-power balance and taking in consideration of the influences of bit geometry, formation characteristics, hydraulic parameters and drilling parameters, a method of estimating formation drilling strength and bit wear by analysis of drilling parameters was advanced. By using the operating parameters of a new bit and according to the description of the coupled actions of bit wear and changes of formation drilling strength, this method creates a possibility of identification of influences formation and bit. With the method described in this paper, a rig-site simultaneous monitoring on drilling operation and diagnosis of downhole abnormal sltuatlons can be made. Meanwhile it can give some quantitative data for after-drilling analysis and bit optimization. Some practical examples are shown also in the paper.