2018 Sucker Rod Pumping Workshop

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

22018 Sucker Rod Pumping Workshop

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

32018 Sucker Rod Pumping Workshop Oklahoma City, OKSept. 11 - 13, 2018

AXIAL AND SIDE FORCES


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.


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


ESTIMATED ROD SHAPE


• 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)


• 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


• 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


• 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


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


Acknowledgements / Thank You / Questions

▪ Thanks to Gyrodata Inc., PL Tech LLC, and EOG Resources for

supplying field data, and for supporting this study.


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)


Superposition gives Fax

max(Fax) needed forrod guide analysis

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2018 Sucker Rod Pumping Workshop

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