Rod Pumping Deviated Wells - ALRDC

1 Rod Pumping Deviated WellsAbstractMore and more directional Wells are being drilled to maximize hydrocarbon recovery and overcomeenvironmental s state-of-the-artpredictive software for rod Pumping can be used to design and optimize rod Pumping in deviatedwells as well as vertical Wells . Previously, traditionalmethods, including wave equation techniques,assume that the wellbore is vertical. Applying these methods to rod Pumping in Deviated Wells and inunintentionally Deviated (crooked) Wells will result in substantial errors and cause inappropriate new technique considers a deviation survey forthe 3-D borehole trajectory and rod/tubing dragfriction in the predictive design paperexamines a real case for a severely Deviated well byusing the new software, showing the best practicesand greater number of Deviated Wells are being drilledto increase production rates, and to minimize costand ecological damage.

2 Sucker rod Pumping has beenan efficient method in vertical Wells and is becomingmore and more common in Deviated Wells . Duringthe last several decades, the Deviated well waspresumed to be a vertical well in the design anddiagnosis of rod Pumping well , which is based on theone-dimensional, viscous-damped wave-equationcomputerized the model for vertical wellis imprecise and not valid for a crooked-hole or adeviated well . In 1992, the 3-D Deviated well modelbased on the modified version of wave equation wasoriginally developed by Dr.

3 Sam Gibbs and has beensuccessfully incorporated into Lufkin Automation sSROD1rod Pumping predictive and design , Lufkin Automation developed and released anew version of the rod Pumping diagnostic program,DIAG, which uses a similar model and algorithm asSROD for diagnosing Deviated paperpresents the new wave equation methodology thatincorporates both viscous friction and drags design procedure for intentionally Deviated well ispresented. Rod guide design is studied. Some otherimportant concerns such as drag friction, guidefriction coefficient, buckling and dogleg servility arediscussed.

4 Finally, the effect of designing an optimumwellbore path before the well is drilled is Xu,Ken Nolen,Dennis Shipp, Andy Cordova,Sam GibbsLufkin Automation 2005 Lufkin is a trademark of Lufkin Automation.(LUF502/0405)NorGlide is a registered trademark ofNorris, a Dover more information 2 Rod Pumping Deviated WellsMathematical ModelGibbs introduced a 3-D modified wave equationmethod to predict and design rod Pumping indeviated governing equation of motionthat is solved to model rod Pumping performance indeviated Wells with rod dynamics, viscous frictionand drag friction is expressed as follows.

5 (1)vrepresents acoustic velocity in the sucker the viscous damping coefficient, whichmodels the effects of fluid viscous friction. (s) isthe friction coefficient function, which provides forvariation of friction coefficient along the rod string(due to bare rods and different types of rod guides).Q(s)and T(s)are functions, which depend on axialload and wellbore deviation. And g(s)is rod gravityeffect. In the vertical well case,g(s) constant andQ(s) T(s) 0; hence, Equation 1 reduces to thewave equation for vertical Wells .

6 A 3-D visualizationof an element of the rod string as a free-bodydiagram in a Deviated well is shown in Figure 1 is solved with the finite differencemethod subject to the complicated boundaryconditions for the pump, surface unit and algorithm is developed in LufkinAutomation s SROD predictive is a comprehensive computerized mathematicalmodel program that is used to design a rod-pumpingsystem in vertical or Deviated latestversion of SROD features a simulation for hydraulicpumping units, such as DynaPump, with dual speedsfor upstroke and downstroke.

7 In addition, gas-enginesimulations have been improved, which includes theeffects of higher fly wheel rotary inertia. Also, indeviated Wells the placement of rod guides, thenumber of guides needed and their added weight tothe rod string are automatically included. 2u(s,t) 2u(s,t) u(s,t) v2 c t2 s2 t u(s,t) (s)[Q(s) T(s)] g(s) sFor more information Considerations in DeviatedWell DesignRod BucklingGenerally speaking, rod buckling can be caused bydownhole rod frictions and faster Pumping effect atfluid pound condition.

8 Some unit geometryselections with faster trip on downstroke thanupstroke may aggravate buckling tendency at fluidpound condition. Under-balanced units may alsoaggravate buckling bottom portion of the rod string in pumpingwells is always in compression from buoyancy ondownstroke, but buoyancy will not cause of a rod string immersed in a fluid isgoverned by the buckling tendency rather than thetrue load or axial true load is useful forcalculating rod-loading base on stress-range diagramssuch as the API Modified Goodman if there is a tendency for rod buckling.

9 One must carefully examine the buckling tendency at the bottom portion of the rod string. Examples of true load (axial load) and buckling tendency are presented in Figure 7 or Figure 11. At depth of 10,116 ft on Figure 11, negative trueload 2842 lbs, buckling tendency difference between them ( 1836 lbs) reflectsthe fluid buoyancy the following equation for criticalload (lbs) necessary to buckle the rod.(2)where I moment of inertia of crosssection d4/64 (in4)E elastic modulus of rod _105(psi, for steel)w weight of rod in fluid wair(1 ) (lbs/ft)Fcritical 3 ( w)2/144page 3 Rod Pumping Deviated WellsThe criteria for buckling is that if the rod bucklingtendency, which includes rod dynamics effect, isgreater than Fcritical, then the rods can be expectedto buckle.

10 However, Equation 2 is only applicable tovertical Guide DesignIn rod Pumping Wells , the most expensive routinewell-servicing cost is the repair of tubing many cases, this wear is caused by side loads froma Deviated wellbore. Also, if rod buckling on thedownstroke is occurring, rod/tubing wear can result,which is typically near the there area few options to reduce rod/tubing wear, rod guidesalong with keeping full pump condition couldpossibly be the most practical and the most cost-effective method of controlling rod buckling androd/tubing wear problems.