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Sucker Rod Pumping WorkshopWyndham Hotel, Houston, TexasSeptember 11 – 14, 2007Over Travel Under TravelFo/Skr & N/N'oLimitsLynn Rowlan
Introduction1. API RP 11L - Figures2. Discuss Properties of Dynamometer Surfaceand Pump Card3. Define Fo/Skr & N/N'o4. Discuss How Increased SPM increasesOvertravel5. Does Fo/Skr & N/N'o Limits Impact RodFailures6.Discuss ALEOC Failure Frequency PlotSept. 11 - 14, 20072007 Sucker Rod Pumping Workshop2
Dynamometer Cards DefinitionKrSurface CardPump CardKtPump CardUnanchoredTubingSept. 11 - 14, 20071) Surface dynamometercard is the plot of themeasured rod loads at thevarious positionsthroughout a completestroke; the load is usuallydisplayed in pounds offorce and the position isusually displayed ininches.2) Pump dynamometer cardis a plot of the calculatedloads at various positionsof pump stroke andrepresents the fluid loadthe pump applies to thebottom of the rod string.2007 Sucker Rod Pumping Workshop3
Normal Pump Card Fluid Load, FoFo – Fluid Load the Pump Appliesto Rod String and caused by thedifferential pressure (Pdis-Pintk)acting across the pump plunger.Surface CardPdis- Pump Discharge PressurePintk – Pump Intake PressureAp – Area of the PlungerSV Open Upstroke:Fo (Pdis - Pintk)*ApFo, Fluid LoadSept. 11 - 14, 2007TV Open Downstroke:Fo 02007 Sucker Rod Pumping Workshop4
API RP 11L Figure
PPRL Peak Polished RodLoad experienced duringa stroke.Normal Dynamometer CardWrf Fo Max (TV) Weightof Rods in Fluid plus thefluid load applied to therods by the pumpWrf (SV) Weight of Rodsin Fluid, TV open andplunger is applying noload to the rods.MPRL Minimum PolishedRod Load experiencedduring the pumping cycle.
TV Weight of Rods in Fluid, Wrf,plus the Fluid Load, Fo, plungeris applying to the rods.Wra weight of the rod stringsuspended in air.Wrf Wra - BuoyancyFo fluid load the pump applies tothe rod string.F1 dynamic force required at thesurface to apply a static forceFo at the pump.F2 dynamic surface force due totransferring the Fo carried by thetraveling valve to the standingvalve.
Example Well1. 5000 ft pump depth, 100 in surface stroke (s),50 psi tubing and pump intake pressure2. 2 inch diameter plunger with anchored tubinga) Fluid Load 6802 lbs3. Tubing Fluid Gradient 0.433 psi/ft4. 76 API Designation rod stringa) 41.2% - 7/8” and 58.8% - 3/4” rodsb) Weight Rods in Fluid – 8,288 Lbsc) Kr 254 lb/in & SKr 25400 lbd) Fo/SKr 0.268 with 26.8 in of Stroke lost to StretchSept. 11 - 14, 20072007 Sucker Rod Pumping Workshop8
Example WellDynamometer Cards at Pumping Speed of approximately 0100 inPeak PR Load, PPRL Wrf FoMin. PR Load, MPRL WrfSPM 026.8 inFo/Skr 0.268
Example WellDynamometer Cards at Pumping Speed of approximately 5 SPM100 inPeak PR Load, PPRL Wrf F1Min. PR Load, MPRL Wrf – F2SPM 5Wrf 8,288 LbsF1 8700 LbsF2 1775 Lbs26.8 in
Rod String 76 Design loaded to 100% of theAllowable Modified Goodman Stress100 inPPRL Wrf F1MPRL Wrf – F2SPM 11Wrf 8,288 LbsF1 11,378 LbsF2 4,100 Lbs26.8 in13.8 in
No - Undamped Natural FrequencySynchronousSynchronous SpeedSpeed ofof StraightStraight UniformUniform SuckerSucker RodRod StringStringNo 15 vs / LNo 15 x 16300 / 5000 48.9No – Undamped natural frequency , SPMvs – Velocity of Sound in Steel, ft/secvs 16,300 ft/secL – Length of Rod String, FtN – Current Pumping Speed, SPMN’o – Natural Frequency adjusted for Taper – Fc x NoFc 1.093N’o 1.093 x 48.9 53.4N/N’o - Dimensionless Speed RatioSept. 11 - 14, 20072007 Sucker Rod Pumping Workshop12
Compares the Plunger Stroke Factor, Sp/S,where Sp is plunger stroke and S is surfacestroke to Fo/Skr and N/No’. N/No’ is theratio of the current pumping speed to theharmonic pumping speed, No’.Fo/SKrAs the value ofFo/SKr goesup, then moreof the surfacestroke is lost tostatic stretch.1105API RP 11LSept. 11 - 14, 20072007 Sucker Rod Pumping WorkshopAs N/No’ increases, then more overtravel occurs13
1st CompanyAPINORP11– Do NotDesign Rods HereDue to OvertravelBADFairBadGoodNO – Do NotDesign Rods HereDue to UndertravelFairSept. 11 - 14, 20072007 Sucker Rod Pumping Workshop14
APINORP11– Do NotDesign Rods HereBAD2ndCompanyFairSaysBadGoodNever DesignFairRods HereSept. 11 - 14, 2007NO – Do NotDesign Rods Here2007 Sucker Rod Pumping Workshop15
Fo/Skr & N/No' Rod Design PracticeFo/Skr1st company’s rod design practicewhere:Fo/SKr 0.2 and N/No’ 0.2 Maximum2nd company designed rod stringswhere:Fo/SKr 0.2 and N/No’ 0.2 MinimumDid design practice impact failure Rates?
Both had 0.4 Failure Frequency.From ALEOC
What did Companies have inCommon?1. Active Program where Technicians:a) Acquired Datab) Analyzed Problemsc) Followed-up Recommendations2. Practiced a “Company” Methodology toAnalyze, Optimize, and Trouble Shoot Wells3. Tracked Cause and Condition of FailedDownhole Equipment in a Failure Data Base4. Determined to investigate Root Cause ofFailure and Correct the Problem.Sept. 11 - 14, 20072007 Sucker Rod Pumping Workshop18
What does the ALEOC FailureData Show?1. Making an effort to analyze the well’s operationand taking action to fix problems discovered isthe MOST important requirement2. Everyone in the study group recognized theirperformance could be improved and they tookaction to reduce failures3. Their different actions with-in their individualcompanies resulted in a reduction of failuresfor all companies in the study group4. Expect a 0.4 Failure Frequency in Your FieldSept. 11 - 14, 20072007 Sucker Rod Pumping Workshop19
Is Overtravel Good or Bad?1. Good because Pump DisplacementIncreases with Increase in SPM2. Bad because Failures “tend” to increasewith increased SPM3. Operating within a pumping speed 5-10SPM range is common practice andfailures rates should not increase whenpumping within this speed range.Sept. 11 - 14, 20072007 Sucker Rod Pumping Workshop20
CopyrightRights to this presentation are owned by the company(ies) and/orauthor(s) listed on the title page. By submitting this presentation tothe Sucker Rod Pumping Workshop, they grant to the Workshop,the Artificial Lift Research and Development Council (ALRDC), andthe Southwestern Petroleum Short Course (SWPSC), rights to:– Display the presentation at the Workshop.– Place it on the www.alrdc.com web site, with access to the site to beas directed by the Workshop Steering Committee.– Place it on a CD for distribution and/or sale as directed by theWorkshop Steering Committee.Other uses of this presentation are prohibited without the expressedwritten permission of the company(ies) and/or author(s) who own itand the Workshop Steering Committee.Sept. 11 - 14, 20072007 Sucker Rod Pumping Workshop21
DisclaimerThe following disclaimer shall be included as the last page of a Technical Presentation orContinuing Education Course. A similar disclaimer is included on the front page of the Sucker RodPumping Web Site.The Artificial Lift Research and Development Council and its officers and trustees, and the SuckerRod Pumping Workshop Steering Committee members, and their supporting organizations andcompanies (here-in-after referred to as the Sponsoring Organizations), and the author(s) of thisTechnical Presentation or Continuing Education Training Course and their company(ies), providethis presentation and/or training material at the Sucker Rod Pumping Workshop "as is" without anywarranty of any kind, express or implied, as to the accuracy of the information or the products orservices referred to by any presenter (in so far as such warranties may be excluded under anyrelevant law) and these members and their companies will not be liable for unlawful actions and anylosses or damage that may result from use of any presentation as a consequence of anyinaccuracies in, or any omission from, the information which therein may be contained.The views, opinions, and conclusions expressed in these presentations and/or training materialsare those of the author and not necessarily those of the Sponsoring Organizations. The author issolely responsible for the content of the materials.The Sponsoring Organizations cannot and do not warrant the accuracy of these documents beyondthe source documents, although we do make every attempt to work from authoritative sources.The Sponsoring Organizations provide these presentations and/or training materials as a service.The Sponsoring Organizations make no representations or warranties, express or implied, withrespect to the presentations and/or training materials, or any part thereof, including any warranteesof title, non-infringement of copyright or patent rights of others, merchantability, or fitness orsuitability for any purpose.Sept. 11 - 14, 20072007 Sucker Rod Pumping Workshop22
API RP 11L - Figures 2. Discuss Properties of Dynamometer Surface and Pump Card 3. Define Fo/Skr & N/N'o 4. Discuss How Increased SPM increases Overtravel 5. Does Fo/Skr & N/N'o Limits Impact Rod Failures 6. Discuss ALEOC Failure Frequency Plot. Sept. 11 - 14, 2007 2007 Sucker Rod Pumping Workshop 3 Dynamometer Cards DefinitionDynamometer Cards Definition 1) Surface dynamometer
