Research Papers: Petroleum Wells-Drilling/Production/Construction

Laboratory Simulation of Drill Bit Dynamics Using a Model-Based Servohydraulic Controller

[+] Author and Article Information
David W. Raymond, Yarom Polsky, Scott S. Kuszmaul

 Sandia National Laboratories, Albuquerque, NM 87185

M. A. Elsayed

 University of Louisiana at Lafayette, Lafayette, LA 70504

J. Energy Resour. Technol 130(4), 043103 (Nov 24, 2008) (12 pages) doi:10.1115/1.3000142 History: Received June 18, 2008; Revised September 05, 2008; Published November 24, 2008

Drilling costs are significantly influenced by bit performance when drilling in offshore formations. Retrieving and replacing damaged downhole tools is an extraordinarily expensive and time-intensive process, easily costing several hundred thousand dollars of offshore rig time plus the cost of damaged components. Dynamic behavior of the drill string can be particularly problematic when drilling high strength rock, where the risk of bit failure increases dramatically. Many of these dysfunctions arise due to the interaction between the forces developed at the bit-rock interface and the modes of vibration of the drill string. Although existing testing facilities are adequate for characterizing bit performance in various formations and operating conditions, they lack the necessary drill string attributes to characterize the interaction between the bit and the bottom hole assembly (BHA). A facility that includes drill string compliance and yet allows real-rock/bit interaction would provide an advanced practical understanding of the influence of drill string dynamics on bit life and performance. Such a facility can be used to develop new bit designs and cutter materials, qualify downhole component reliability, and thus mitigate the harmful effects of vibration. It can also serve as a platform for investigating process-related parameters, which influence drilling performance and bit-induced vibration to develop improved practices for drilling operators. The development of an advanced laboratory simulation capability is being pursued to allow the dynamic properties of a BHA to be reproduced in the laboratory. This simulated BHA is used to support an actual drill bit while conducting drilling tests in representative rocks in the laboratory. The advanced system can be used to model the response of more complex representations of a drill string with multiple modes of vibration. Application of the system to field drilling data is also addressed.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Laboratory simulation of drilling dynamics

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Figure 2

Mechanical analog versus model-based control

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Figure 3

Drilling facility with a mechanical analog of a drill string. The inset shows the bit used for the drilling tests.

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Figure 4

Bit motion and measured WOB from drilling tests with a mechanical analog

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Figure 5

Effect of drill string dynamics on bit response and resulting rate of penetration

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Figure 6

Model-based control approach

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Figure 7

Dynamics simulator for model-based control

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Figure 8

Force capacity and displacement response for servohydraulic actuators used in simulation (17)

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Figure 9

Input voltage (top) to actuator controller and actuator displacement response (bottom)

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Figure 10

Transfer function for the servohydraulic actuator derived using systems identification

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Figure 11

Block diagram to determine control voltage for a given displacement

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Figure 12

Transfer function for the mechanical analog (bold lines represent measured data; dashed lines are fit)

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Figure 13

Implementation of the simulator to produce a given response for a drill string

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Figure 14

Agreement between the predicted and measured displacements for the proof-of-concept demonstration

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Figure 15

Bit response for the proof-of-concept drilling test in the time and frequency domain

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Figure 16

Dominant modes from the normal mode model used in predictor

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Figure 17

Drilling record from the model-based control simulation using the normal mode predictor

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Figure 18

Bit response with the normal mode predictor in the time and frequency domain

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Figure 19

Magnitude of the normal mode model transfer function




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