Field Validation of a New Bottomhole-Assembly Model for Unconventional Shale Plays

Abstract

Summary A new drillstring model has been developed that determines the static and dynamic behavior of bottomhole assemblies (BHAs) in 3D wellbores. An attempt at validating this model with field data is presented, and it shows a close agreement between observed and calculated downhole BHA behavior. Validation tests were conducted using high-frequency downhole data measured within a motor-assisted rotary-steerable BHA. The gathered data were used to verify the calculated mechanical loads, predicted lateral natural frequencies of the BHA, estimated directional performance of the downhole assembly, and the torsional resonance resulting from high-frequency torsional oscillations (HFTOs). Results from the field tests show a strong correlation between measured and calculated bending-moment values, as well as lateral natural frequencies of the BHA, with an average of 3% error across all data sets. The primary source of error is thought to be borehole spiraling, which is quantified through analysis of the downhole bending-moment data. In addition, the model is shown to provide close estimates of the actual directional performance of both steerable mud motors and rotary-steerable BHAs. However, the directional-calculation vs. -measurement comparison does reveal a need to incorporate a rate-of-penetration (ROP) dependency within the directional-prediction algorithms.