Abstract
As the drilling industry enters the era of big data, it has become necessary to find ways to organize and understand the vast amounts of real-time high frequency data recorded.
Shor et al. (2014) show that real-time accelerations recorded down hole actually differ from those predicted by various models, either in the high frequency range or at peak values. These differences in vibration levels can be attributed to noise from various sources, such as the motor or surface equipment, design of measurement devices, uneven shape of the borehole, and/or dynamic effects, such as dampening/cushioning of fluids, bit rock interactions, drillstring-borehole wall interactions, etc. These differences can cause real-time drill log analysts to miss instances of actual failure or predict false failures.
The industry currently focuses on the peak and average values of the accelerations recorded down hole, and there is no established method to examine the trend of these accelerations. The methodology proposed in this paper first focuses on obtaining the actual unmodulated acceleration values from the recorded downhole gauge data and then processes these values to understand the trend of acceleration as the drilling proceeds. This demodulation (or deconvolution) of the recorded data can reduce the likliehood of false predictions and, at the same time, increase the credibility of the mode of acceleration predicted (and hence more accurately predict failure), which currently relies only on the experience of the engineer. Thus, this technique can make real-time data monitoring more reliable and simple. Further, if combined with a gamma ray log to know the lithology of the formation being drilled, this data monitoring technique can reveal a significant amount of information.
In addition, this paper suggests calculating instantaneous jerk intensity and decomposing it to its monotonic intrinsic mode function. This reveals that these monotonic functions follow a certain trend, which might be useful in future endeavors to understand the underlying physics of drillstring failure.
