2018 Sucker Rod Pumping
WorkshopCox Convention Center, Oklahoma City, OK
September 11 - 13, 2018
Rod-guide Placement Based on High-
Resolution Tortuosity Analysis of
Production Tubing
Onyemelem Jegbefume; Jon Bang; Adrián Ledroz; Rob Shoup, Gyrodata Inc
Robert Vincent, PL Tech LLC
Joseph Earley, EOG Resources
CONTENTS
• Background• Forces
• Rod shape
• Estimation of rod shape
• Tortuosity analysis -> Contact points -> Description by curve
• Results
• Conclusions
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Oklahoma City, OKSept. 11 - 13, 2018
THE NEED FOR ROD GUIDES
• In Rod-driven pumping, the rod string is moved up
(upstroke) and down (downstroke) repeatedly inside the
production tubing.
• Bending in the rod string and production tubing causes
rod/tubing contact at various depths.
• Friction at the points of contact will cause wear on both the
rod and production tubing
• To reduce wear, rod guides are installed at depths where
high frictional forces between the rod string and tubing are
expected
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AXIAL AND SIDE FORCES
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Johancsik et al. 1984; SPE-11380-PA Wave equation model (Gibbs 2012; textbook)
TORTUOSITY; REDUCTION OF EFFECTIVE DIAMETER
• In an earlier paper (Bang et al. 2016), a number of parameters for the characterization of tortuosity were described
• One tortuosity parameter is the effective diameter of a straight device that can be placed inside the casing or tubing
• The length of the device is specified
• Bending in wellbore => effective diameter is less than wellbore diameter
• The higher the degree of bending around a specific depth in the wellbore, the lower the effective diameter at that point.
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CONTACT POINTS
• Assume that the first contact point CPn has been found at measured depth MD(CPn)
• From point MD(CPn), straight lines (rays) are drawn to points on the center line further down the well, and transversal distances between each ray and the center line are calculated.
• If the maximum transversal distance = tubing radius, the ray is touching the tubing, => contact point CPn+1
• The procedure is repeated from point MD(CPn+1) on the centerline
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ESTIMATED ROD SHAPE
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• A minimum-energy (ME) curve is fitted
between each pair of contact points,
with rod string locations and tangents at
the contact points as constraints.
• The inclination IME and azimuth AME of
the minimum-energy curve trajectory are
found at selected locations (rod section
ends) between the contact points
• IME and AME at both ends of a rod section
are used in the wave model, replacing
the traditional I and A from the tubing
survey.
RESULTS 1
Comparison of results from low resolution and high resolution data (proposed method)
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• Side forces from low and high resolution data differ significantly
• Low resolution data misses some small scale bending which
results in lower calculated side forces and a recommendation of
fewer guides
RESULTS 1 (contd.)
Comparison of side forces from proposed method and commercial
software
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• Side force curve from proposed method exhibits a similar general
trend as that from commercial software
• Differences in magnitude are caused by the use of different input
trajectories and assumptions in both methods.
RESULTS 2
Comparison of side forces from proposed method and commercial software
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• Similar trend in both results
• Proposed method indicates need for additional rod guides at
certain depths
DISCUSSION OF RESULTS
• MD locations of contact points cannot be confirmed easily, thus, the accuracy of our results cannot be quantified until enough data is gathered and analyzed.
• Side forces from proposed method are similar to results from the traditional method
• Results may be presented differently
• Side forces shown may be restricted to peaks exceeding threshold level, to simplify the plots
• Tabular listing of depths/side forces
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CONCLUSIONS
• A new method for estimating the trajectory of the rod string
in the production tubing was presented; main features:
• Determination of contact points from high resolution data
• Fitting of a curve through the contact points
• Traditional open hole MWD survey is replaced with
estimated rod shape in side force analysis
• Comprehensive use of all available survey data is expected to
improve the accuracy of the results => better decisions on
placement of rod guides
• Reliability of the proposed method needs confirmation
through feedback from field cases in which the new method
is applied
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Acknowledgements / Thank You / Questions
▪ Thanks to Gyrodata Inc., PL Tech LLC, and EOG Resources for
supplying field data, and for supporting this study.
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Analysis of rod motion (Dynamometer)
• Wave equation (Sam G. Gibbs: SPE 1165; textbook «Rod
pumping»)
• Static solution: Udispl_stat(x) and Fax_stat(x)
▪ Rod weight
▪ Buoyancy
▪ Tapered rod
▪ Inclined wellbore
• Dynamic solution: Udispl_dyn(x,t) and Fax_dyn(x,t)
▪ Friction
▪ Boundary dynamometer: at pump or polished rod
▪ Details of motor and pump are ignored
▪ Approximations: single rod section; straight rod (for U, F
analysis)
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Superposition gives Fax
max(Fax) needed forrod guide analysis
Copyright
Rights to this presentation are owned by the company(ies) and/or author(s) listed on the title page. By submitting this presentation to the Sucker Rod Pumping Workshop, they grant to the Workshop, the Artificial Lift Research and Development Council (ALRDC), and the Southwestern Petroleum Short Course (SWPSC), rights to:
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▪ Place it on a CD for distribution and/or sale as directed by the Workshop Steering Committee.
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Disclaimer
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Oklahoma City, OKSept. 11 - 13, 2018
The following disclaimer shall be included as the last page of a Technical Presentation or Continuing Education Course. A similar disclaimer is included on the front page of the Sucker Rod Pumping Web Site.
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