This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 112650, "Drilling- Vibrations Modeling and Field Validation," by J.R. Bailey, SPE, E.A.O. Biediger, SPE, V. Gupta, SPE, D. Ertas, SPE, W.C. Elks, SPE, and F.E. Dupriest, SPE, ExxonMobil, originally prepared for the 2008 IADC/SPE Drilling Conference, Orlando, Florida, 4-6 March. The paper has not been peer reviewed.
A modeling tool has been developed that enables drilling engineers to design vibration-resistant bottomhole assemblies (BHAs), given tool-placement constraints and desired directional objectives. This model can be applied to configurations with the majority of common drilling components. Modeling results have been validated in large, intermediate, and small hole sizes. Redesign has resulted in improved drilling results, including increased on-bottom drilling time, longer tool life, higher rate of penetration (ROP), reduced nonproductive time associated with tripping, and better hole quality.
Vibration of drillstrings and BHAs has contributed to operational problems since rotary drilling was first invented. Failure of drillstring components, such as rotary-steerable (RS) BHAs or logging-while-drilling (LWD) tools, may result in nonproductive time while tripping to replace the failed equipment. Downhole components may eventually part so that fishing or sidetracking operations are required. In some situations, equipment failure also can result in well abandonment. In addition to these unplanned events, whirl or lateral vibration causes the cutting action of the bit to be inefficient, and ROP may decline significantly. The operator drills approximately four million ft of hole each year, and mechanical-specific-energy (MSE) analysis suggests that the performance in more than 40% of this footage is affected adversely by whirl.
At various times in the past, investigators have focused on certain elements of the drillstring-dynamics problem and have made some progress, to be succeeded by new theories using generally more-complicated models. The current activity is marked by an emphasis on digital-data collection using both surface and downhole instruments, and the use of time-domain modeling to take advantage of increasing computing power. The full-length paper represents an attempt by the operator to strike a forward path by maximizing the benefits of both worlds: using digital systems to take measurements only recently made possible and developing and using sophisticated frequency-domain dynamic-modeling tools to characterize the dynamic performance of BHAs.