Petroleum Wells-Drilling/Production/Construction

Model Development of Torsional Drillstring and Investigating Parametrically the Stick-Slips Influencing Factors

[+] Author and Article Information
Parimal Arjun Patil

e-mail: parimal.patil@tu-clausthal.de

Catalin Teodoriu

Institute of Petroleum Engineering,
Clausthal University of Technology,
Agricola Str. 10, Clausthal-Zellerfeld,
Niedersachen 38678, Germany

1Corresponding author.

Contributed by the Petroleum Division of ASME for publication in the Journal of Energy Resources Technology. Manuscript received July 9, 2012; final manuscript received October 19, 2012; published online December 12, 2012. Assoc. Editor: W. David Constant.

J. Energy Resour. Technol 135(1), 013103 (Dec 12, 2012) (7 pages) Paper No: JERT-12-1158; doi: 10.1115/1.4007915 History: Received July 09, 2012; Revised October 19, 2012

Drillstring vibration is one of the limiting factors maximizing drilling performance. Torsional vibrations/oscillations while drilling is one of the sever types of drillstring vibration which deteriorates the overall drilling performance, causing damaged bit, failure of bottom-hole assembly, overtorqued tool joints, torsional fatigue of drillstring, etc. It has been identified that the wellbore-drillstring interaction and well face-drill bit interaction are the sources of excitation of torsional oscillations. Predrilling analysis and real time analysis of drillstring dynamics is becoming a necessity for drilling oil/gas or geothermal wells in order to optimize surface drilling parameters and to reduce vibration related problems. It is very challenging to derive the drillstring model considering all modes of vibrations together due to the complexity of the phenomenon. This paper presents the mathematical model of a torsional drillstring based on nonlinear differential equations which are formulated considering drillpipes and bottom-hole assembly separately. The bit–rock interaction is represented by a nonlinear friction forces. Parametric study has been carried out analyzing the influence of drilling parameters such as surface rotations per minute (RPM) and weight-on-bit (WOB) on torsional oscillations. Influences of properties of drillstring like stiffness and inertia, which are most of the times either unknown or insufficiently studied during modeling, on torsional oscillation/stick-slip is also studied. The influences of different rock strength on rate of penetration (ROP) considering the drilling parameters have also been studied. The results show the same trend as observed in fields.

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Fig. 1

Schematic of a drilling process with input and output parameters

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Fig. 2

Modeling torsional drillstring

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Fig. 3

Representation of a drillstring as a torsional pendulum driven by a top drive motor

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Fig. 4

Torsional drillstring model using matlab/simulink interface

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Fig. 5

Effect of surface RPM (80–120) on bit speed

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Fig. 6

Effect of surface RPM (120–80) on bit speed (axis reversed for surface RPM in Fig. 5)

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Fig. 7

Effect of surface RPM on rate of penetration

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Fig. 8

Effect of WOB on bit speed

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Fig. 9

Effect of WOB on rate of penetration

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Fig. 10

Effect of drillstring stiffness on bit speed

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Fig. 11

Effect of drillstring stiffness on rate of penetration

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Fig. 12

Effect of drillstring inertia on bit speed

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Fig. 13

Effect of drillstring inertia on rate of penetration

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Fig. 14

Effect of confined compressive strength of rock on ROP

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Fig. 15

Effect of stick-slip influencing parameters on rate of penetration




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