Bit Performance

Abstract Models for Bearing Wear, Teeth Wear and Penetration Rate of bits have been developed Penetration Rate of bits have been developed which give reasonably good correlations on Louisiana Gulf Coast and Offshore data sets. In addition to the usual significant variables reported in the literature, bit hydraulic horsepower and bit mechanical horsepower have both been found to be significant variables not only in the Penetration Rate models but also in the Penetration Rate models but also in the Bearing Wear and Teeth Wear models. A Torque Oscillation Meter (TOM) has been developed and three prototypes have been successfully used for the last two years in the real time monitoring of bit condition and other downhole conditions to obtain maximum economic bit life, and further enhance bit performance. performance Introduction The need to incorporate bit performance into optimum well planning has grown in importance as the industry has ventured into more expensive areas. The environmental effect of mud systems on bit performance has been difficult to appraise but the advent of the sealed bearing bit has greatly reduced the mud system as a significant variable except for its weight and viscosity effects, which are more readily characterized and accounted for. BIT BANK In order to efficiently gather, correlate and use bit performance a data bank was initiated in September, 1972. About 100 bits per month are deposited in this data bank and this paper reports on the first 9 months of operation. Utilization of the data bank in predicting bit performance for optimum well planning is just performance for optimum well planning is just commencing. Six data sets have enough bits to report on preliminary correlation results. Deposits, retrievals and correlations are done from each of three Louisiana operating offices, although at this early stage of exploratory model building on bit performance, the correlation work has been largely done in New Orleans. The bank is resident in San Francisco and readily accessible from all four locations. A continuing effort is being made to obtain reliable data. Bit grading needs to be done consistently according to prescribed procedures. Bearing grading is the most difficult of the gradings. At the suggestion of one of the major bit manufacturers a quantitative measure of bearing wear is accomplished with a jig and dial micrometer to measure the lateral movement of the bit cone as it is rocked back and forth on its shank. These are standard machine shop items that are readily available with a magnetic clamp to hold it firmly on the bit leg with the loosest cone. They are kept aboard the rig to grade the bit as soon as it is pulled from the hole.