A database consisting of 150 bit runs over 29 wells was compiled. Trend analysis was performed on the data to determine the driving force behind downhole shocks. A statistical analysis, specifically used for analyzing fatigue life phenomenon, was used to predict a Mean Shock Between Failure (MSBF) for a downhole tool component

Data analysis revealed that high shock levels occurred in both horizontal and vertical wells. The analysis also confirmed that downhole vibration is a strong function of RPM and WOB. The data shows that pendulum assemblies with tricone bits using high WOB results in extremely high levels of downhole shocks.

Downhole shock data transmitted in real time will allow the operator to vary drilling parameters to reduce the downhole shock level and increase the life of the drillstring and its components. The data demonstrates that cumulative shock cycles should be used with cumulative pump time to enhance BHA component reliability through improved maintenance scheduling.

Keywords:
pendulum assembly, failure database, vibration, cumulative shock cycle, weibull analysis, drilling operation, frequency, probability, statistical analysis, inclination
Subjects:
Well Planning, Drillstring Design, Drilling Operations, Information Management and Systems, Trajectory design, Directional drilling
Copyright 1991, Society of Petroleum Engineers
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