Keynote Lecture: DPM Depth-time Algorithm for Eliminating the Random Variations in MWD Penetration Rate-PPT Presentation

PPT Presentation

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The presentation addresses the substantial random fluctuations in penetration rate recorded by measurement-while-drilling (MWD) systems. These variations make it difficult to identify homogeneous ground layers and their boundaries from penetration-rate profiles alone, despite MWD’s potential for rapid, economical subsurface characterization.<br /><br />It presents the Drilling Process Monitoring (DPM) time-series algorithm, developed at the University of Hong Kong. The method converts drilling measurements into a curve of bit depth against net drilling time, then identifies linear sections. Each section represents an interval with an approximately constant penetration rate; changes in slope indicate potential layer boundaries. Applied to MWD data, this approach can reduce the effects of noisy depth-series penetration rates and support clearer ground profiling.<br /><br />Three case studies illustrate the method. In London Clay, the algorithm identified major zones and subzones, with inferred boundaries compared against geological information from core samples. In weathered argillaceous limestone along a tunnel alignment, it segmented three boreholes into linear zones and helped profile variations in rock mass quality. Laboratory drilling through two sandstone blocks of contrasting strength showed that the method detected the interface through a change in the displacement–time curve, with results consistent across different drilling conditions.<br /><br />The presentation concludes that MWD records the drilling process but its raw penetration-rate output is often too variable for reliable layer identification. By applying the DPM time-series algorithm to MWD data, practitioners can derive constant-rate intervals and more effectively identify strata and interfaces. Penetration rate should still be interpreted alongside other drilling variables when assessing ground conditions.

Keywords

measurement-while-drilling

MWD

penetration rate

Drilling Process Monitoring

time-series algorithm

ground profiling

strata boundaries

linear sections

London Clay

subsurface characterization