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Chapter 7A.

Matrix StimulationPetroAcademy Module

Artificial Lift Introduction

Reciprocating Rod Pump Fundamentals

Artificial lift rod pump wellcompletions comprise thelargest number of wellmechanical completiondesigns in the industry

A broad web search of rodpump data leads to theconclusion that the world’spopulation of producing wellsis around 1,000,000• Of these wells, between 90%

and 94% of them are onartificial lift

• About 85% to 90% of theseare estimated to be rod pumptype completions

Why Take This Module?

Reciprocating Rod Pump Fundamentals ═════════════════════════════════════════════════════════════════════════

© PetroSkills, LLC. All rights reserved._____________________________________________________________________________________________

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Conventional Unit

Mark II Unit






Air Balance Unit

Hydraulic Unit

Long Stroke Unit



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Dynamometer

This module reviews in detail,the design and operationengineering and principles ofa rod pump’s surface unit, rodstring, and downhole rodpump, the three primarycomponents of a rod pumpcompletion

The standard rod pumpperformance analysis tool, thesurface dynamometer, ispresented in detail


Well site controller technologyis introduced as well ascorrosion control principles forrod pumps

Learning how an operationsengineer responsible for rodpumps can take advantage ofthe available analytical toolsto maximize production from arod pump while minimizingundue stresses on the surfaceunit, rod string, and downholepump components will resultin minimal pump failures andgreatly reduced operatingcosts and downtime

Controller



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Well site controller technologyis introduced as well ascorrosion control principles forrod pumps

Learning how an operationsengineer responsible for rodpumps can take advantage ofthe available analytical toolsto maximize production from arod pump while minimizingundue stresses on the surfaceunit, rod string, and downholepump components will resultin minimal pump failures andgreatly reduced operatingcosts and downtime



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Chapter 7A.

Matrix StimulationPetroAcademy Module

Artificial Lift Reciprocating Rod Pump

Components and Operational Principles


Learning Objectives

This section will cover the following learning objectives:

Apply the working principles and operating characteristics ofoilfield reciprocating rod pump artificial lift technology

Illustrate using pictures, animations, sketches, design software,and other media and tools the key mechanisms of rod pumpsystems



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Rod Pump System Components

Rod Pumps are also Called Beam Pumps*

1. Surface Equipment2. Sucker Rods3. Downhole Pump

Analytical Techniques for:• Prime Mover System• Rods• Pump at Reservoir Depth

Reservoir inflow from producing zone

Module Contents

Reciprocating Rod Pump Components and Operational Principles Different elements of a pump, how they work, and why

Pump Size / Pump Design

Rod Pump Surface Unit Nomenclature, API specification, surface unit configuration

Rod Pump Rod String How rod string is designed, how stretch is incorporated and why

Rod Pump Downhole Pump Several types of downhole pumps, and their attributes and features

Dynamometer Analysis Dynamometer determines load on the pump at different positions

Failures and Maintenance Important to understand how and why failures occur and how to prevent them

Controllers Designed to manage performance of the surface unit

Summary



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Module Contents









Summary

Introduction to Rod Pumps – Terminology

The pumping unit changes the rotary motion of the prime mover into reciprocating motion which is transferred to the downhole pump

via the sucker rod string.

Equalizer

Pitman

Gear

Prime Mover

Center Iron (Saddle Bearing)

Rotary counter balance

Crank

Sampson Post

Clamp

Walking BeamHorsehead

Carrier Bar (Stirrup)

Polished Rod

Stuffing Box

CasingSucker Rods

Tubing

Pump

Casing Shoes



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Typical Rod Pump Applications

Well and reservoir conditions• Low to medium producing rates

– Typically used at relatively low rates often with high water cut

• Low productivity conditions– Normally applied where lift has to be achieved entirely by the artificial

lift system

• Low producing bottomhole pressure• Low solution gas ratios

– Gas occupying space reduces the efficiency of a pump

– Important to be able to handle fluids with low solution gas ratios andalso be able to remove gas before gas enters the pump

• High temperature at producing depth• High viscosity produced fluids• Corrosive fluids and overall corrosive conditions• Low operating costs compared to other artificial lift techniques

Group 2 Well Characteristics

Wells less than 4000 ft(1220 m) deep and

Have a pump diametergreater than 2 inches(5.08 cm)


Wells greater than 4000 ft(1220 m) deep and any pump diameter, or

Have a pump diameterless than or equal to 2inches (5.08 cm)

Group 1 and Group 2 Rod Pump Wells

Group 1 Group 2



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Wells less than 4000 ft(1220 m) deep and

Have a pump diameter greater than 2 inches (50.8 mm)


Wells greater than 4000 ft(1220 m) deep and anypump diameter, or

Have a pump diameter less than or equal to 2 inches (50.8 mm)

Group 1 and Group 2 Rod Pump Wells

Each of the above groups has unique features

Analyzing Group 1 and Group 2 Rod Pump Wells

Dynamometer data and softwareprograms are the primary diagnostictools for modern rod pump wells

Surface diagnostic data measuringthe load on the rod string as afunction of position throughout theupstroke / downstroke rod pumpcycle is used to predict downholeloads on the pump

Modern diagnostic analysiscomputer programs providequantitative analysis to distinguishbetween mechanical pumpproblems (e.g., leaking or wornpump) and fluid issues (gas, lowproductivity zones, etc.)



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Group 1 Well Features (> 4000 ft or <4000 ft and Dpump < 2 in)

A majority of industry rod pumps world wide

Rod loading is the main restriction to increased rate due to greater well depth(must reduce pump size)

Surface polished rod dynamometer load shape analysis is a function of manyfactors:

• Pump depth

• Rod string material

• Rod string design

• Pump speed

• Pump unit type

• Pump fillage

• Prime mover type, etc.

Downhole calculated dynamometer load shape is a function of pump condition only

Rods act as “shock absorber” to limit fluid inertia forces; rod elongation / stretch isexpected but it must remain within the elastic limit of the rods

Surface dynamometer shape is difficult to analyze

Calculated downhole dynamometer shape is necessary to analyze pumpperformance

(1220 m) (1220 m) (50.8 mm)

Group 2 Well Features (< 4000 ft and Dpump > 2 in)

Much smaller percentage of rod pumped wells Larger pump used for greater productivity wells Large fluid inertia forces compared to Group 1 wells Large pump sizes, large rates, fast speeds Both surface and downhole dynamometer shape a function of:

• Pump condition• Pump depth• Pump speed• Pump size, etc.

Fluid inertia forces significant in high rate wells• Can double plunger load

Shallower depths (short rod string) so limited “shock absorber” effectof the rods

Less rod stretch Surface dynamometer shape difficult to analyze Calculated downhole dynamometer “predictive” shape is necessary

to analyze pump performance

(1220 m) (50.8 mm)



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Can you describe the difference between

Group 1 and Group 2 rod pump completion configurations?

Pause and Reflect

Learning Objectives

By the end of this lesson, you will be able to:

Apply the working principles and operating characteristics ofoilfield reciprocating rod pump artificial lift technology

Illustrate using pictures, graphics, animations, sketches, designsoftware, and other media and tools the key mechanisms of rodpump systems

This section has covered the following learning objectives:



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Pump Design


Learning Objectives


Employ the steps necessary to design, maintain, and servicerod pump rod strings



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Module Contents









Summary

What Size Pump? What Rate Can the Well Make?

Use Inflow Performance Tools to Estimate Rate• The accuracy of the reservoir fluids inflow rate estimate accuracy

determines the overall pump system performance• Typical Inflow calculation for oil well sucker rod pump design

Pfbhp Below Bubble Point use Vogel Method

Sucker Rod Pump Analysis and Design



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Well Pressure Terminology

Pres – Reservoir pressurePwf – Flowing bottom hole pressure

(wf – well flowing)Pftp – Surface pressure

(ftp – flowing tubing pressure)Psep – Separator inlet pressure(Pres - Pwf) – is referred to as “drawdown”

Pwf

Pump will be sized based upon thereservoir capability to produce fluids.

Determination of a zone’s productivityrequires knowledge of both Pres andthe Pfbhp (or Pwf).

Sketch illustrates rods, downholepump, liquid level, gas in annulus,casing pressure, tubing pressure,bottomhole pressure.

Liquid level is above pump intake.

Rod Pump Design Starts with Inflow (Rate) Determination

PBHP

FL

Pt

Pc

Pump

Oil + Gas

Gas

Liquid



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PBHP

Fluid Level

Gas

Pt

Pc


Engineers use acoustic surveys todetermine bottomhole pressures.

A remotely fired gas gun with a precisionpressure transducer to measure casingpressure change as an acoustic signalmeasures the distance h' to the fluid level.

May be carried out for both flowing andshut-in rod pump wells.

from: Echometer

Pump

Oil + Gas

Liquid

Knowing h, then:

h x fluid gradient = PBHP

PBHP - for both flowing and shut-in conditions

Knowing the distance to the liquid levelfor both flowing and shut in conditionsallows engineers to determine the heightof the fluid level above the pump h.

PBHP

Gas

Pt

Pc

Oil + Gas


H

Pump

H - Distance to the producing zone

h' – From acoustic surveys

h = H – h'

h Fluid Level

Liquid



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Sucker Rod Pump Design and Analysis

• Use longest stroke as practical• Use slowest speed as practical• Use smallest pump as practical• Use as large a pump inlet as practical

• The reservoir fluids inflow rate estimate accuracy determines theoverall pump system performance

• Typical Inflow calculation for oil well sucker rod pump design

General Recommendations to Maintain Production

Use Inflow Performance Tools to Estimate Rate

Pfbhp Below Bubble Point use Vogel Method

Vogel Inflow Calculation

Where:Pwf = Bottomhole flowing pressurePres = Maximum shut-in bottomhole pressure

The relationship provides Q as a function of Pwf

This information is required to design the system

Vogel IPR Curve

2max/ 1 0.2 / 0.8 /wf res wf resQ Q P P P P



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Nodal Analysis principles illustrate how flow from the reservoir to thewell is observed, measured, and managed.

The curve above illustrates one method to quantify how reservoirenergy provides flow rate to a well as a f(Pres - Pwf).

Pwf

Pres

Qliquids

From Nodal AnalysisTM



Pwf

Pres

Qliquids


For (Pres = Pwf)…Q = 0



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Pwf

Pres

Qliquids

For (Pres - Pwf )

For successively greater drawdown, Q increases,

thus, this is an Inflow Curve




Pwf

Pres

Qliquids

For (Pres - Pwf )

For successively greater drawdown, Q increases,

thus, this is an Inflow Curve


By managing Pwf, engineers manage drawdown

The greater the drawdown, the greater the expected ratefrom the well

Engineers can design a specific drawdown to achieve aspecific rate



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Back to Work Suggestions


Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.

Meet with a reservoir engineer or production engineer in your organization to review how inflow relationships are developed to properly size the capacity of your oil well rod pump completions.

Courtesy: Lufkin Industries

Determination of Pres, Pwf, estimated fluid rate, fluid level in well, etc.

(kPa)

(10,342)

(3,206)

(10,342)

(m3/day)

(31.8)

(7.95)

(39.8)

(m)

(3,048)

(3,048)

(392)

(566 kPa/m)

(kPa)

(3,206)

(1,276)

(36.9 m3/day)

(9.2 m3/day)

(46.2 m3/day)

(32 m3/day)

(8 m3/day)

(40 m3/day)

Typical Data Gathering and Rod Pump Planning Review

Production Potential Using Vogel Analysis Software



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Courtesy: Lufkin Industries

Determination of Pres, Pwf, estimated fluid rate, fluid level in well, etc.

(kPa)

(10,342)

(3,206)

(10,342)

(m3/day)

(31.8)

(7.95)

(39.8)

(m)

(3,048)

(3,048)

(392)

(566 kPa/m)

(kPa)

(3,206)

(1,276)

(36.9 m3/day)

(9.2 m3/day)

(46.2 m3/day)

(32 m3/day)

(8 m3/day)

(40 m3/day)

Typical Data Gathering and Rod Pump Planning Review

Production Potential Using Vogel Analysis Software

KEY POINTS

These analyses provide a guide to inflow rateand therefore, accurate pump sizing

These analyses are regularly conducted aspart of routine surveillance activity

A rod pump artificial lift completion is being evaluated and the expected rate needs to be reviewed.

Use the Vogel Inflow relationship to assess the productive zone’s expected rate.

The oil bubble point pressure is 2881 psig (19863.8 kPa) based upon lab analysis.

A valid well test measurement is available where the well Pwf = 1602 psig (11045.4 kPa) with a flow rate of 403 bfpd (64.1 m3) and water cut of 20% and reservoir pressure = 2165 psig (14927.2 kPa).

Estimate the well inflow rate at a Pwf = 1000 psig (6894.8 kPa).

Scenario

Determine

Exercise: Estimate the Expected Inflow Rate Using Vogel IPR



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A rod pump artificial lift completion is being evaluated and the expected rate needs to be reviewed.

Use the Vogel Inflow relationship to assess the productive zone’s expected rate.

The oil bubble point pressure is 2881 psig (19863.8 kPa) based upon lab analysis.

A valid well test measurement is available where the well Pwf = 1602 psig (11045.4 kPa)

with a flow rate of 403 bfpd (64.1 m3) and water cut of 20% and reservoir pressure = 2165 psig (14927.2 kPa).

Estimate the well inflow rate at a Pwf = 1000 psig (6894.8 kPa).

Scenario

Determine

Solution

Q = Qmax (1 - (20% (Pwf/Pres) - 80% (Pwf/Pres)2)

Qmax = 973 bfpd (155 m3/d)

Q at Pwf = 1000 psig = 717 bfpd (6894.6 kPa = 114.0 m3/d)

Exercise: Estimate the Expected Inflow Rate Using Vogel IPR

Module Contents









Summary



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Learning Objectives

By the end of this lesson, you will be able to:


This section has covered the following learning objectives:



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Rod Pump Surface Unit


Learning Objectives


Employ the steps necessary to design, maintain, and servicerod pump surface unit equipment



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Rod Pumps are also Called Beam Pumps*

Analytical Techniques for:• Prime Mover System• Rods• Pump at Reservoir

Depth

Reservoir inflow from producing zone

The three major components of a rod pump system:

Sucker Rods

Downhole Pump

Surface Equipment

The Surface Unit



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Rod Pump Surface Unit Types

Wellhead

Long stroke polished rod

Hydraulic cylinder actuator

RotoflexTM Unit

Long Stroke Polished Rod Pump

The Rotoflex has twosprockets connected bya large chain

On the front of the unit is alarge, reinforced steel belt

• This connects to thepolished rod in the well

Can produce significantrates [2,000–3,000 bbls/day(318 – 477 m3/d)] from a depthof about 3,000 ft. (914 m)



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Conventional Unit• Usually lowest cost unit

• Can be set up to rotate clockwise or counter clockwise

• Works well with fiberglass rods

• Usually lower maintenance costs

• Less counterweight required compared to others

Mark II Unit• Usually more efficient than others

• Usually has lower torque requirements

• Often costs less

Air Balanced Unit• Compact, yet largest available size

of all units

• Least weight of all units

• Can be set up to rotate clockwise or counter clockwise

Most Common Units – Some Advantages and Disadvantages

Ad

van

tag

esA

dva

nta

ges

Conventional Unit• Gear reducer requirements often

large

• Less efficient than other units

Mark II Unit• Can only rotate counter clockwise

• Often not a fast as other units

• Cannot use fiberglass rods (due to potential rod compression possibilities)

Air Balanced Unit• More complex than others

(compressor, overall maintenance)

• Air cylinder water condensate build up possibilities, other)

Disad

vantag

esD

isadvan

tages

Rotoflex Unit• Can achieve high production rates

due to long stroke

• System efficiency very high

• Much smaller prime mover required than other units

• Much lower gearbox loading

• Minimizes load reversal cycles due to long stroke length and low strokes per minute

• Easy to work on well by sliding unit away from well on its tracks

Hydraulic Units• Used for very deep wells

• Often has built in dynamometer

Most Common Units – Some Advantages and Disadvantages

Ad

van

tag

esA

dva

nta

ges

Rotoflex Unit• Costly

• Stroke lengths up to 300 in (7620 mm) require large, long pumps

Hydraulic Unit• Higher maintenance costs

• Complex hydraulics, therefore breakdown frequency

Disad

vantag

esD

isadvan

tages



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Review the types of reciprocating rod pump units that are in service in your company’s oil well completions.

Analyze the reasons for each type.

Review your analysis with an experienced production engineer.

BOTTOM OF DOWNSTROKE

TOP OF UPSTROKE

Rod Pump Operating

At the top of the upstroke, the unithas lifted well fluids one strokelength and the rods to the surface.

At the bottom of the downstroke,the unit has lowered the rods backinto the well one stroke length.

One half rod pump cycle illustrated

Maximum load

occurs

Minimum load

occurs



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On the downstroke, thegearbox lifts thecounterweight with the helpof the rod load (to get thecounterweight ready to helpagain on the upstroke).

On the upstroke, thecounterweight releasesenergy to the gearbox andhelps the gearbox by falling.

Rod Pump Operating

TOP OF UPSTROKE

BOTTOM OF DOWNSTROKE

The Mark II unit offset (195o vs 180o) crank geometry effectively reduces rod acceleration at the beginning of the upstroke when load is greatest, thereby effecting a reduction in the polished rod load.

Conventional Unit Crank

Mark II Unit Rod Pump Offset Crank Angle

The maximum upstroke torque required (when lifting rods and fluid load) is reduced and the maximum downstroke torque (lowering rod load in fluid back into the well) is increased.

Mark II Unit Crank



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Pause and Reflect

Can you name two advantages and two disadvantages for a Conventional rod

pump unit and for a Mark II unit?



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See API Specification 11E

Rod Pump Surface Unit API Designation

C-228D-246-86

A – Air Balance

B – Beam Balance

C – Conventional

M – Mark II

LP – Low Profile

RM – Reverse Mark

Polished Rod Rating in

100s of LBFs (pounds force)

Maximum Stroke

Length in Inches

PK Torque Rating in

Thousands of IN-LBS

API Gearbox Ratings API Structural Ratings API Standard Stroke’s, in (m)

80 48 (1.2)

114 143 54 (1.4)

160 173 64 (1.6)

228 200 74 (1.9)

320 213 86 (2.2)

456 246 100 (2.5)

640 256 120 (3.1)

912 305 144 (3.7)

1280 365 168 (4.3)

1824 427 192 (4.9)

2560 470 216 (5.5)

240 (6.1)

Rod Pump Surface Unit Configurations

Standard API Unit Sizes



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168 in.(4267 mm)

Example: Rod Pump Surface Unit Identification

C-912D-365-168 Conventional UnitC-912D-365-168 Conventional Unit

Designate:• Well on right and the surface unit on the left• Counter Clock Wise (CCW) or Clock Wise (CW) rotation• Cranks fall towards Sampson Post is called positive rotation• Cranks fall away from Sampson Post called negative rotation

912,000 in-lbs.(10,507 m-kg)

36,500 lbs.(16,556 kg)

Pause and Reflect

If the number “168” were replaced by the number “154” in the rod pump description C-912D-365-168, what would that

signify?



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Sucker Rod Pump Design and Analysis

Operating loads are influences by several factors:• Deviated or crooked holes• Fluid viscosity• Specific gravity of the produced fluids• Pumping fluid levels

Diagnosis of actuator, pump, and rod performance is performedby a strain gauge tool called a dynamometer.

Rod Pump Data Gathering and Design

Loads on the rod string as a function of the position of the rod string reciprocationand position of the rod are continuously measured for analysis.

A strain gauge on the polished rod measures these loads on the pump upstrokeand downstroke.

The pictured tool which gathers this data is called a “dynamometer.”



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Load vs. Position of Walking Beam and Rods

… discussed in greaterdetail later in module

Rod Pump Idealized Dynamometer Card Analysis

Traveling Valve Closing Recoil

Rods & Fluid being lifted

Max LoadWalking Beam Decelerating

Polish Rod Up

Standing Valve Taking Over Load

Rods & Plunger Falling Through

Fluid

Min Load

Walking Beam Decelerating

Load Increase

Polish Rod Down



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Prime Mover Motor, Sheaves, and Belts

Motor turns sheaves• Motor normally electrical• Gasoline and diesel

engines have been used

Belts connect sheaves togear box

Purposes of belt drive• Provides speed reduction• Allows pumping speed

change• Provides soft link in drive

train• Moves motor away from

cranks

Sheaves and Gear Box

Typically beam pumpmotors are running 1200or 1800 RPM (RevolutionsPer Minute)

Need a method to reducespeed to get down toapproximately 10 SPM(Strokes Per Minute)

Use ratio of sheaves andgearbox

Gear box sheave

Prime mover (electric motor)

sheave



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Gear Reducer Box Illustration

Case Head Removed For Lubrication Maintenance

Reduces RPM by a factor of 30Increases torque as a function of 30

1170x 12" / 47" = 298.7 RPM(305 mm / 1194 mm)

RPM x DMS / DGB = ____ RPMRPM x DMS / DGB = ____ RPM

Sheaves / Gear Box Design and Strokes / Minute

How Sheaves and Gearbox Convert Motor RPM to Rods SPM

Gear Box Sheave 47 in. diameter (1194 mm)

298.7 RPM30.12 GB Ratio

= 9.92 SPM

Motor RPM1170 RPM

Motor Sheave12 in. diameter (305 mm)

Gear Box Ratio30.12



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Rod Pump Strokes Per Minute Exercise

The rod pump motor works with the gear box to convert therotational rpm’s of the motor into the reciprocating motionrequired by the rod pump at the downhole pump.

• A rod pump has a motor sheave of 10 in. (254 mm) O.D.

• The gear-box sheave is 34 in. (864 mm) O.D.

• The gear box is a standard 30:1 ratio unit.

• The motor is a gas engine turning at 500 rpm average speed.

Rod Pump Strokes Per Minute Exercise

10" / 34" =10" / 34" =

RPM x 0.294 =500 x 0.294 =

147.1 RPM

RPM x 0.294 =500 x 0.294 =

147.1 RPM

4.9 SPM4.9 SPM

0.294

The rod pump motor works with the gear box to convert therotational rpm’s of the motor into the reciprocating motionrequired by the rod pump at the downhole pump.

• A rod pump has a motor sheave of 10 in. (254 mm) O.D.

• The gear-box sheave is 34 in. (864 mm) O.D.

• The gear box is a standard 30:1 ratio unit.

• The motor is a gas engine turning at 500 rpm average speed.

(254 mm / 864 mm)

147.1 RPM / 30 =



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SLIP = (No-Load RPM – RPM Under Load) / (No-Load RPM)

Oil Field Rod Pump Motor Types

Type~ Efficiency

Full LoadSlip

Starting Torque

Application

NEMA B ~92+ 2 – 3% 100 – 175% Transfer Pumps

NEMA C ~90+ 4% 200 – 250%Positive

DisplacementInjection Pumps

NEMA D ~88% 8 – 13% 275%+ Beam Pumps

ULTRA HIGH SLIP

Lower 15 – 30% 275%+Special

Application Beam Pumps

NEMA D Beam Pumps8 – 13% 275%+8 – 13% 275%+



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The motor provides external energy input to work with the gearbox, crank arm, and counterweight to lift rods and fluids out of thewell on the upstroke and lower rods back into the well on thedownstroke… for each cycle.

Wrist Pin

Pitman Arms

Rod Pump Crankshaft / Counterweight

Counterweight

Gear Box

Crank Arm

Pause and Reflect

Can you explain the difference between a rod heavy and counterweight heavy unbalanced pump

cycle torque requirement?



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Gather data regarding NEMA D electrical motor loads and determine if motor / gear box data indicate unbalanced torque conditions.


Recommend rod pump set‐up changes if recorded motor load data illustrate an unbalanced torque condition.

Oil Field Rod Pump Motor Types

Balanced vs. Unbalanced Motor• Below are the torque (in-lbs or m-kg) or kW (power) signatures of an

electrically or mechanically unbalanced or balanced pumping unit

Balanced if the peak upstroke torque is equal to the peak downstroke torque

Balanced if the peak upstroke torque is equal to the peak downstroke torque

One Pump Cycle One Pump Cycle One Pump Cycle

Torq

ue/

Po

wer

Up DownUp DownUp Down

Rod Heavy Weight Heavy Corr. CB Moment

Mechanical/Electrical Unbalanced Balanced



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Elbow connection 2-7/8" (73 mm), 8R

Pumping well Stuffing box Blow out preventer Gas side check valve

• Gas must be capable offlowing from casing back intoflowline through check valve

Flowline pressure

Production Tree With Provision for Annular Gas

Re-Entry into Flowline

Surface Installation for Rod Pumping Units

Polished rod clamp 2 bolt, 40,000 lbs(18,144 kg), 1-1/4" (32 mm) or

1-1/2" (38 mm) PR

Bridle and carrier bar for C228 and M320 units

Stuffing box DPSB male thread, WP 1500 psi

(10,342 kPa)Rod BOP 2-7/8" (73 mm), 8R male x female, WP 1500 psi

(10,342 kPa)

Pumping T 2-7/8" (73 mm)

WP 1500 psi, EUE 8R 2" (51 mm) L.P. X 1/2" (13 mm)

NPT

Needle valve1/2" (13 mm) NPT


Swage 2" (51 mm) L.P. X 1/2" (13 mm) NPT

Swage 2" (51 mm) L.P. X 1/2" (13 mm) NPT

Companion flange 2-1/16" (52 mm),

3M X 2" L.P.

Nipples 2-7/8" (73 mm)

8R variable length 4"-12" (203-305 mm)

T connection2-7/8" (73 mm), 8R

Flow check valve 2-7/8" (73 mm) WP 1,500 psi

(10,342 kPa), 8R

Flow check valve 2-7/8" (73 mm) WP 1,500 psi

(10,342 kPa), 8R

Ball valve 2-7/8" (73 mm) WP 1,500 psi (10,342 kPa), 8R


Companion flange 2-1/16" (52 mm), 3M

X 2" (51 mm) L.P.




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Rod Pump Rod String


Learning Objectives



Design a rod pump rod string using the Modified Goodmanmethod

Highlight the considerations and adjustments being reviewed byAPI regarding standards for proper consideration of rod fatigueand related corrosion effects upon rod string design



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Module Contents









Summary

The Rod String



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The Rod String

Rods are carefully evaluated at the surface, whenthey are pulled, and when they are run.

Rods must be free from corrosive environments, or ifin a corrosive environment, properly inhibited toaddress corrosion issues.

If the unit is also running tubing, the completion rig ison-site in order to run the original completion in thewell.

C - 90,000 psi min. tensile (620,528 kPa)

K - 90,000 psi min. tensile(620,528 kPa)

D - 115,000 psi min. tensile(792,897 kPa)

High strength rods 140,000 psi in. tensile (965,266 kPa)

API Grade Rods

46.2%

6 / 8

API 86 Rod String

Rods equally stressed

Rods designed with equalfatigue failure tendency

8 / 8

Equal Stress

Tapered String

The Rod String (Rod Pump Sucker Rods)

7 / 8

1.5 in. Pump – (38 mm)

26.8%, 27%,



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Rod Pump Rods

Grade C Sucker Rod Designed to be used with low and medium loads in non-corrosive or effectively

inhibited wells. Manufactured in 1530 Mod. steel.

D Carbon Sucker Rod Grade Designed for moderate loads in non-corrosive or effectively inhibited wells.

Manufactured in 1530 Mod. micro-alloy steel.

Grade K Sucker Rod Designed for low and medium loads in corrosive wells, which are recommended

to inhibit. Manufactured with AISI 4621 Mod. steel.

KD Special Grade Sucker Rod (Critical Service) Designed for moderate to heavy loads in corrosive wells, however an effective

inhibition program is recommended to minimize damaging effects. Manufactured in AISI 4320 Mod. steel.

D Alloy Grade Sucker Rod Designed for moderate to heavy loads in non-corrosive or effectively inhibited

wells. Manufactured with AISI 4142 Mod. steel.

Different grades and materials are offered, based on the load typeand corrosive environment of the wells where they will be used.

Rod Pump Rods – Steel Grades and Mechanical Properties

From: Tenaris



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Pause and Reflect

Can you explain the stress/strain relationship of a rod string within the elastic limit of

the steel of the rod?

Does the rod string steel permanently

deform?

Stress Strain Curve

Rod Pump Rod Design

Rod Stress / Strain Curve• Sucker Rods should operate

in the linear portion of thestress vs. stain curve andnever undergo permanentdeformation.

• Rod Fatigue is, however, themain design consideration forcontinuous operation.

• Per API standard, when thedifference between (rangeof) the maximum andminimum actual stress onrod string is great, theallowable rod stress isdecreased. See the Modified Goodman Rod Design

Method Illustrated on the Following Slides

Tensile Strength

Yield Stress

Modulus of Elasticity

Rupture Stress

Permanent Deformation

Str

ess

(P

SI)

Strain (IN/IN)



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SA = SA – Smin

SA = Max allow stress psi

SA = Allow stress range

0.5625 = Slope of SA curve

SF = Service Factor

T = Min tensile strength

T

Construction of Modified Goodman Diagram

T

T/1.75

SA

Sm

T

T

Rod Pump Rod Design

T/4

SA (T/4 + 0.5625 (Smin)) (SF)=

Rod Pump Rod Design

Service Factors (SF) de-rate theallowable rod stress

Service Factor Guidelines• Use C grade rods to SF of 1.35

before using D grade rods• Use D grade rods to SF of 1.35

before going to hi strength rods• Inhibit well; do not use case

hardened rods• From failure control in rod pump

wells ‐ SWPSC

Service API-C (default)

API-D (default)

Non Corrosive

1.0 1.0

Salt Water 0.65 0.9

H2S 0.5 0.7

Note: At present, API is in the process of: (a) studies to justify increasing rod stress allowables (as most rod failures are related to other than stress related causes; i.e., failure due to corrosion, couplings, etc. failures), and (b) studies to justify changing the T/1.75 Modified Goodman variable to approximately T/1.28).T/1.75 T/1.28



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Rods Design Example: Get Surface Rod Loads from Dyno Card

Lo

ad,

lb.

Polished Rod Position

Pk Load = 17,900 lbs. (8,119 kg)

Stress = 29,768 psi (205 MPa)

Min Load = 9,100 lbs. (4,128 kg)

Stress = 15,141 psi (104 Mpa)

Dynamometer Card Rod Area is .601 in2 (15.3 mm2)

Rod Diameter is .875 in(22.2 mm)

(8,165)

(9,072)

(7,257)

(6,350)

(5,443)

(4,536)

(3,629)

(2,722)

(1,814)

(907)

(kg

)




Analyze the rod string design for a few typical wells in your area.


Participate in developing/writing any required pulling unit or rig workover field programs to pull/run new rod strings (and possibly related tubing and downhole pump change outs).



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37,267 – 15,141

Smin = 15,141 psi(104 Mpa)

Sucker Rod Design – Modified Goodman Diagram

T/1.75

T/4

0

S.F. = 1.0

29,768 – 15,141

= 66%

Rod Loading

115,000 psi (7,929 Mpa)

Pk Stress = 29,768 psi(205 MPa)

SA = (T/4+.5625(Smin))(SF)

= 37,267 psi(257 Mpa)

205 -104257 -104

= 29,814 psi

Smin = 15,141 psi(104 Mpa)

Sucker Rod Design – Modified Goodman Diagram

SA = (T/4+.5625(Smin)) T/1.75

Pk Stress = 29,768 psi

0

S.F. =

SF = 0.8

T/4

(.8)

15,141 psi

0.8

37,267 – 15,141

29,768 – 15,141

= 66%

205 -104257 -10429,814

= 99.7%

115,000 psi (7,929 Mpa)

(205 MPa)

Rod Loading

At 99.7%, rods are at limit.

205 -104206 -104

(206 Mpa)



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Sucker Rod Couplings

These couplings are made of 8630 alloy steel and offer excellent resistance to hydrogen embrittlement. The base metal is prepared to a No. 1 finish per NACE TM0170 or TM0175 before spray weld coating is applied. This provides a strong metallurgical bond between base metal and the spray metal coating.

CO-HARD couplings incorporate a spray weld coating for maximum corrosion/abrasion resistance to hydrogen embrittlement. They are intended for use with rods where coupling abrasion wear or coupling corrosion is a problem.

Mechanical Properties

Tensile 100,000 psi (min) Hardness 56-62 HRA SM Coating Thickness 0.010” to 0.020” SM Coating Hardness 595 HV200(min).

From: Weatherford

Grade T Sucker Rod CouplingsGrade T Sucker Rod Couplings

These API Class T couplings are made of 8630 alloy steel and offer excellent resistance to hydrogen embrittlement. They are furnished with all Weatherford sucker rods unless otherwise specified.

Grade SM CO-HARD Sucker Rod CouplingsGrade SM CO-HARD Sucker Rod Couplings

Measured CircumferentialDisplacement

ScribedVertical

Line

Sucker Rod Makeup Torque

For Correct Make-Up, LubricateThreads Before Make-Up

For Correct Make-Up, LubricateThreads Before Make-Up

Made-Up JointMade-Up JointHand Tight JointHand Tight Joint



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Sucker Rods: COROD

From: Weatherford

Ad

van

tag

es

Disad

vantag

es

• Cost possibly up to five times higherthan comparable conventional rod

• Service rig and welding unit must beavailable in the area for servicing

• Connection to polished rod and pullrod critical

• No couplings• Minimal pin and coupling failures• Minimal rod and tubing wear• Minimal torque and power

requirement• Enhanced pump efficiency• Simple, quick, installation and

field service



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Rod Pump RodsReciprocating Rod Pump Fundamentals

═════════════════════════════════════════════════════════════════════════

© PetroSkills, LLC. All rights reserved.

_____________________________________________________________________________________________ 51

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Rod Pump Downhole Pumps


Learning Objectives


Employ the steps necessary to design, maintain, and servicerod pump downhole pumps



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Module Contents









Summary

Different down hole pipes are run differentlyDifferent down hole pipes are run differently

Individual types of down hole pumpsIndividual types of down hole pumps

Major Rod Pump System Components

Features and nomenclature according to API

Distinction is made in what type of pump to use forparticular applications



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Downhole Sucker Rod Unit Pumps

Rod Pumps are either of 2 types:

Rod Insert Pumps

Tubing Pumps

Rod Insert Pumps With pumps seated at the bottom of tubing

• Run into tubing on wireline and can be changed out• Classified as top hold down, bottom hold down, or

traveling barrel

Tubing Pumps With the pump built into the tubing wall

• These pumps cannot be pulled by wireline to change outor service the unit

• Because the pump is built into the tubing wall, it is largerand produces at a higher rate than rod insert unit

Pause and Reflect

Can you describe the difference between a

rod insert pump and a rod tubing

pump?



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Review the percentage of tubing pumps installed compared to the number of insert pumps.

Analyze the reasons for each.


THTubing Pump

RWATop Hold

Down Pump

RHBBottom

Hold Down Pump

RWTTraveling

BarrelPump

Top Hold Down• RWA – Thin Wall• RHA – Heavy Wall

Bottom Hold Down• RWB – Thin Wall• RHB – Heavy Wall

Traveling Barrel• RWT – Thin Wall• RHT – Heavy Wall

Tubing Pumps

API Pump Classifications



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API Downhole Pump Classifications

ROD INSERT PUMPSTUBING PUMP

TH

Top Hold Down

Bottom Hold Down

Traveling Barrel

RWA RHB RWT

Bottom Hold Down• RWB – Thin Wall• RHB – Heavy Wall

Insert pump• Most popular of four

types of rod pumps• Not used in sand

producing areas• Hold down seal

profile at bottom



TH

Top Hold Down

Bottom Hold Down

Traveling Barrel

RWA RHB RWT

Top Hold Down• RWA – Thin Wall• RHA – Heavy Wall

Insert pump• Good for sand

production• Settling sand has

lesser effect• Pump not as rugged

as bottom holddown



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TH

Top Hold Down

Bottom Hold Down

Traveling Barrel

RWA RHB RWT

Traveling Barrel• RWT – Thin Wall• RHT – Heavy Wall

Insert pump• Heavy particulate

production• Traveling barrel

keeps sand inmotion above thehold down

• Traveling valve onpump top



TH

Top Hold Down

Bottom Hold Down

Traveling Barrel

RWA RHB RWT

Tubing Pumps

Tubing pump• Most rugged• Higher rates• Plunger assembly

and standing valvecan be pulled withrods

• Barrel cannot bepulled by rods as itis part of the tubingstring



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Four Basic Down Hole Pump Parts

Cylindrical barrel

Hollow plunger

Intake or standing valve

Exhaust or traveling plunger

Various API Down Hole Pump Components

API Rod Pumps

Valve Cages

Balls& Seats

PumpHold Down Seal Assemblies



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Tubing Size

Type of Pump and Location of

Seating Assy

Length of Barrel

Plunger Size Length of Plunger

Length of Extensions

From: Weatherford

Rod Pump Downhole Pump API Designation

20: 2-3/8 in. (60 mm) tubing

125: A 1-1/4 in. (32 mm) bore rod type pump with:• 10 ft. (3 m) heavy wall barrel

• 1 ft. (.3 m) lower and upper extensions

• 4 ft. (1.2 m) plunger

• Bottom cup type seating assembly for operations in 2-3/8 in. (60 mm) tubing

RHBC: Type of pump

20-125-RHBC-10-4-1-1

Note Tubing Sizes / First Two Digits

API Specification 11AX – Downhole Rod Pump Naming Convention

Tubing size: 15 [1.900 in. (48.3 mm) OD] 20 [2⅜ in. (60.3 mm) OD] 25 [2⅞ in. (73.0 mm) OD]30 [3½ in. (88.9 mm) OD]40 [4½ in. (114.3 mm) OD]



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Gas Anchors

Gas Anchor ExamplesGas Anchor Examples Gas Anchors

• Gas occupies space in anypump interference and candrastically reduce rodpump efficiency.

• Gas should be separateddownhole to as great anextent as possible andvented up the casing.

• A gas anchor with theseating nipple below wellperforations is the bestoption.

• If a rat hole is not present,then determine the bestgas anchor for the well.

Casing

Tubing

Rods

Pump

Seating Nipple

Mud Anchor

“Natural” Anchor

Modified “Poor Boy”

Anchor

Rods Casing

Tubing

Pump

Seating Nipple

Suction Tube

Anchor Intake Perforation

Producing

Zone

Producing

Zone

Pause and Reflect

Can you explain the purpose of a rod pump gas anchor?



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Rod Pump Dynamometer Analysis


Learning Objectives

BThis section will cover the following learning objectives:

Describe how a rod pump surface dynamometer gathers rodpump loading data over each pump cycle

Calculate maximum and minimum rod stress loading

Predict downhole pump performance

Select rod string taper sizing

Select motor horsepower required

Evaluate overall pump performance while identifying rod pumpproblems, all using a rod pump dynamometer, known as TheAnalytic and Predictive Tool for reciprocating rod pumps



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Module Contents









Summary

Dynamometer Analysis

The original dynamometer was a mechanical device that worked with fluidacoustic equipment

• Clamped onto the polished rod as it moved up and down

• A stylus moved across a drum and traced the polished rod load vs. the positionof the dynamometer on wax paper

• The resulting data was called a dynamometer card

Modern dynamometers are used to diagnose many different pumpingsystem problems

Before modern dynamometers, dynamometer cards were the primarymethod for diagnosing problems

• Individual operators needed much experience to compare data to typicalexamples and find issues

• Data histories are valuable in helping understand diagnostic problems or thecondition of the system

Today’s equipment and technologies are based on determining down hole,at-the-pump dynamometer data conducted using the wave equation, adifferential equation, and computer programs



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Dynamometer Instrument Example

1. Pump off control polished rod load cell

2. Horseshoe load cell dynamometer

3. Horseshoe cell and string positiontransducer basket

4. Clamp on load transducer

5. String transducer clamp

1

2

3

4

5

Overtravel *

Undertravel *

Fluid Load

Friction

Gas Interference

Pump-off

Other

Loose Tubing Anchor

Traveling Valve Problems *

Standing Valve Problems *

Pump Leakage

Pump Sticking

Fluid Pound *

Typical Problems Identified by Dynamometer Analysis

* Each of the problems notedare illustrated on other slides.



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Overtravel *

Undertravel *

Fluid Load

Friction

Gas Interference

Pump-off

Other

Loose Tubing Anchor

Traveling Valve Problems *

Standing Valve Problems *

Pump Leakage

Pump Sticking

Fluid Pound *

Typical Problems Identified by Dynamometer Analysis

* Each of the problems notedare illustrated on other slides.

Rod Pump Polished Rod

The polished rod is the connecting link betweenthe surface pumping unit and the downhole rodstring.

The polished rod’s exterior surface is ground toclose tolerances and has an extremely smoothsurface to provides a sealing surface for theelastomer seals (packing) that allow polish rodvertical movement.

Sucker Rod O.D.

5/8 in. (16 mm)

3/4 in. (19 mm)

7/8 in. (2.2 mm)

1 in. (25 mm)

Polished Rod O.D.

1-1/8 in. (29 mm)

1-1/8 in. (29 mm)

1-1/4 in. (32 mm)

1-1/2 in. (38 mm)

Recommended Polished Rod Sizes



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Load vs. Position of Walking Beam and Rods

Rod Pump Idealized Dynamometer Card Analysis

Traveling Valve Closing Recoil

Rods & Fluid being lifted

Max LoadWalking Beam Decelerating

Polish Rod Up

Standing Valve Taking Over Load

Rods & Plunger Falling Through

Fluid

Min Load

Walking Beam Decelerating

Load Increase

Polish Rod Down

Dynamometer Data

Dynamometer cardanalyzes the dynamics ofthe pumping system.

• Load = Weight of the rodstring and fluid.

• Position = Inclination ofthe beam.

• Dynagraph = Plot of loadvs. position for one fullpump cycle.

Analysis software• Upload dynamometer

cards to PC.• Analyzes cards and

makes recommendations.



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Surface Dynamometer Load Data and Calculated Pump Load Data

A plot of measured rod loadthroughout one continuouspump cycle.

Rod load is in lbs-force.

Rod position is in inches.

A plot of calculated rod load intubing fluid Wrf throughout onecontinuous pump cycle.

Represents the load Fo whichthe pump applies to the bottomof the rod string in lbs-force.

Surface Load Data From Dynamometer

Downhole Pump Data Calculated

Lbs – FX 1000

inches

Surface Dynamometer Data

Downhole Pump Data

Surface Load DataFrom Dynamometer

Downhole Pump DataCalculated

(4 m)

(N x 1000)

(100)

(89.0)

(77.8)

(66.7)

(55.6)

(44.5)

(33.4)

(22.2)

(11.1)

(-11.1) (4.3 m)



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Downhole Pump Upstroke and Downstroke Performance

Tubing

Sucker Rods

Casing

Plunger

Traveling Valve

Working Barrel

Standing Valve

Sucker Rod Pump Cycle

Upstroke Downstroke

Traveling Valve Check

1. Set up and checkdynamometer

2. Start pump and assureproper pumping action

3. Stop the unit on theupstroke (apply brakesmoothly)

4. Hold for 10 seconds+

5. If the load remainsconstant for 10 seconds+,then the traveling valveand plunger are in goodcondition

6. Repeat test



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Standing Valve Check

1. Set up and checkdynamometer

2. Start pump and assure properpumping action

3. Stop the unit on the downstroke(apply brake smoothly)

4. Hold for 10 seconds+

5. If the standing valve is holdingthe weight of the fluid load andremains constant (orincreases), then the travelingvalve will not be picking up aload if the standing valve wereleaking and the standing valveis thus in good condition. If thestanding valve load drops, thetraveling valve has not opened.

6. Repeat test

Pause and Reflect

Can you describe when the rod pump standingvalve opens?

Can you describe when the rod pump travelingvalve opens?



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Historical Rod Pump Design Methods

Mills Method (1940s – manual calculations)• Clarified initial rod pump physics and geometry• Early attempts to understand pump and rod forces

API RP 11L (1950s – analog “average” model)• Assumes: pump full, anchored tubing, low slip motor, steel rods

only, no fluid acceleration, unit fully in balance, no downhole friction, no dynamic inertia effects, for wells > 2000 ft (610 m), etc.

Wave Equation (1960s)

Expert Wave Equation (1990s)

Computer based mathematics to solve the Wave Equation rod string model

Wave Equation

The Wave Equation is an important second-order linear partialdifferential equation for the description of waves as they occurin physics… such as sound waves, light waves and waterwaves.

Applicable to disciplines like acoustics, electromagnetics, andfluid dynamics.



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For Modern State-of-the-Art ComputerBased Rod Pump Design

A partial differential equation that doesnot have an exact solution.

a - Velocity of sound in steel (ft/sec or m/sec)c - Damping coefficient (1/sec)t - Time (sec)x - Distance from polished rod (ft or m)u (x,t) - Displacement (ft or m)

Wave Equation

2 22

2 2

( , ) ( , ) ( , )u x t u x t u x tc

t x t

Use of computers in theiterative method ofsuggesting a solution andtesting it repeatedly allowsthe Wave Equation to beused because of the speedand capabilities of thecomputer application

Basic equation for rod pumpanalysis, and models theelastic behavior of the rodstring

Represents forces that areaxial along the rod, includingfriction

Friction due to fluid inertiadepends on relative velocitybetween rods moving andthe fluids

Fo – Plunger fluid load N – Pump speed (strokes / minute)

S – Surface stroke length No – Natural frequency of tapered rod string

Kr – Spring constant of rod string

Diagnostic Analysis Application• Calculate downhole dyno as f(polished rod dyno)

Fo / SKr – Dimensionless rod stretchN / No – Pump speed / natural frequency of tapered rod string

The Wave Equation Applied

• Used as a design analysis application• Predict the dyno for a given system

Predictive / Design Analysis Application



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Peak Polished Rod Load (PPRL)

Top of Stroke

Gross Plunger Load (Fo)

Weight of Rods in Fluid (Wrf )

Polished Rod Position

Pol

ishe

d R

od L

oad

Dynamometer Load Trace

0

S

Unanchored Tubing

Bottom of Stroke

Minimum Polished Rod Load (MPRL)

Surface Dynamometer Load DataCalculated Downhole Pump Load

Actual Rod Pump Dynograph Diagnoses – Poor Setups

Line Current vs PositionLine Current vs Position

Surface and Pump CardsSurface and Pump Cards

(19,463 kg)

(8,354 kg)

Reducer Torque vs PositionReducer Torque vs Position

(72.8 M N-m)

(-8.4 M N-m)

Pump Velocity vs PositionPump Velocity vs Position

(1.77 m/s)

(1.96 m/s)



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Common Calculated Downhole Shapes and Interpretation

Pump FullTubing Anchored

Slight Fluid Pound Tubing Anchored

Severe Fluid PoundTubing Anchored

Completely Pumped Off Tubing Anchored

Leaking TravelingValve or Plunger

Leaking StandingValve

MalfunctioningTubing Anchor

Severe Fluid PoundTubing Not Anchored

Slight Fluid Pound Tubing Not Anchored

Pump Full Tubing Not Anchored Anchor Failure

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.1 0.2 0.3 0.4 0.5 0.6

Undertravel and Overtravel on Polished Rod Dyno

o

N

N

o

r

F

SK



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0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.1 0.2 0.3 0.4 0.5 0.6

o

N

N

o

r

F

SK

Undertravel RegionStroke at Pump

Much Smaller than at Surface

High Failure Frequency N/N0

Above 0.35


Overtravel RegionStroke at Pump

Much Longer than at Surface

N is the number of strokes per

minute

F0 is the load on the pump

Ideal Dynamometer

Load

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.1 0.2 0.3 0.4 0.5 0.6

o

N

N

o

r

F

SK

Undertravel RegionStroke at Pump

Much Smaller than at Surface

High Failure Frequency N/N0

Above 0.35


Overtravel RegionStroke at Pump

Much Longer than at Surface

N is the number of strokes per

minute

F0 is the load on the pump

Ideal Dynamometer

Load

In Summary:• By reducing N (number of strokes per minute),• Increasing S (stroke length), and• Using a smaller sized pump with a therefore lesser load…

Movement away from the overtravel or undertravel extremes would put the dynamometer data more in the central portion of total range



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Surface Dynamometer Load Data and Calculated Pump Load Data

Maximum rod load during upstroke

PPRL – Peak Polished Rod Load

Calculated Downhole Dyno

Rod weight in fluid plus fluid loadapplied to rod by the pump

Wrf + F0 Max (TV – Traveling Value)

Rod weight in fluid with TV openand pump applying no load to rod

Wrf (SV – Standing Valve)

Minimum rod load during downstroke

MPRL – Minimum Polished Rod Load

Actual Surface Dyno Data

MPRL

Lb(f) x 1000

Position (inches) (4267 mm)

(3960m m)

(89.0)

(77.8)

(66.7)

(55.6)

(44.5)

(33.4)

(22.2)

(11.1)

(N x 1000)

Pause and Reflect

Do you understand the meaning of the rod pump acronyms PPRL and MPRL?



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Analyze dynamometer data from a few typical wells in your area and evaluate the range of identified rod pump problems observed from dyno data.

Review your findings with an experienced production engineer.

Visit several wells during dynamometer and controller installation and witness rod pump start up procedures/operations.



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Rod Pump System Failures and Maintenance


Learning Objectives


Outline the primary causes of rod failure and how the use of rodguides and other auxiliary equipment can mitigate failures, theeffect of gear box overload and how to prevent it, the properselection of rod metallurgy for corrosion conditions, and theneed for disciplined inspection of well tubing and rods tominimize failures



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Module Contents









Summary

Sucker Rod Failures and Maintenance

Loss of Circumferential Displacement

Coupling Wear



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Causes of Sucker Rod Failures

A key API study underway is recognizing that most rod pumpfailures are due to well corrosion environments rather thanfatigue stress which is the basis for most rod designs.

Rod parting and tubing failures are often related to sideloading and resultant tubing and rod wear in deviated holes.

Critical Factors to Minimize Pump Downtime

Inspection• Recommend inspection of

both new and used rods

Handling• Transport, pickup, running

(0.8 mm)

(0.1 mm)

(0.5 mm)

(0.4 mm)

(0.3 mm)

(0.2 mm)

ROD INSPECTION (API IIB (SPEC)

Threads:(Gauges)

End Cracks: (Magnaglow)

Parallelism:(Feeler Gauge)

End Finish:(Comparitor)

Stamping:(Pit Gauge)

UpsetSurface Finish:(Magnetic Flux Leakage)

BodySurface Finish:(Magnetic Flux Leakage)

DimensionalTolerances: (Micrometer)

Maximum Allow Bend in 1 FootBody – 0.130 in.Ends – 0.200 in.

(3.3 mm)

(5.1 mm)

Thread Dimensions CheckedWith Go–No–Go Gauges API

Check forImperfections and Cracks

No Gap Greater Than 0.003 in. (5.1 mm)

250 RMS

No Greater Than 0.031 in.

0.0625 in Imperfection (1.6 mm)

Traverse – 0.004 in.Longitudinal – 0.020 in.

Diameter – 0.016 in.+ 0.008 in.

Out of Round – 0.010 in.

(25 mm)Rod

Straightness:(Straight Edge

Gauges)



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Recommended Sucker Rod Practices

Rod Guides• Use guides at wear locations such as dog-leg and locations just

above the pump to reduce wear due to fluid pound.• Molded guides tend to slip less than hand installed guides.• When dog-leg conditions are severe, guides are required for future

pump completions.

Pause and Reflect

Do you understand and can you describe the

purpose of rod string rod guides?



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Recommended Sucker Rod Practices

Rod Rotators• Rod rotators are used in conjunction with

rod guides to remove paraffin deposition.

• A rod rotator should not be used when rodscan’t rotate freely. If the rods torque up,backlash could cause the rods to unscrew.

• A leveling plate should be installed on thecarrier bar to prevent misalignment thatcould cause side loads that could result ina polish rod failure.

• A rotating tubing hanger and anchorsystem is available that can be installed onwells that have severe wear problems.

• The entire tubing string can be slowlyrotated to distribute wear from rod contact,even if sides loads keep the rod string incontact with one side of the well. It isrelatively expensive but it can be justified ifit eliminates one tubing failure in a well.

• Use tubing rotator if tubing wears.

The rotator body rests on the cross bar and the polish rod clamp rests on the rotating body hub.

Fiberglass Sucker Rods

• Light weight, thereforereduced load on surfaceequipment.

• Due to elasticity, welldesigned rod stringscan have longer strokedownhole than surfacestroke over travel toincrease production.

• Suitable for corrosiveenvironments.

Po

siti

ve C

on

sid

erat

ion

sP

osi

tive

Co

nsi

der

atio

ns

• Higher cost compared toconventional steel grade suckerrods.

• Due to elasticity and stretch, whenfluid load increases (water cut %increases), the downhole pump stroke is smaller than surfacestroke.

• Rod surface area damages morequickly compared to steel rods.

• Due to fiber compositemanufacturing, fiberglass rods cannot support compressive loads and must always be in tension.

• Rod design is critical and pump-offcontrollers are highly recommended to eliminate any compression due to unforeseen problem downhole.

• Extremely difficult to fish whenrods part.

Neg

ative Co

nsid

eration

sN

egative C

on

sideratio

ns



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When to Use Fiberglass Sucker Rods

Straight holes

Bottomhole temperature less than 220° F

Pump depths greater than 4000 ft

As alternative to severe, repeated corrosion problems

To design overtravel into system to obtain increasedrate

Rod Pump Field Automation Diagnostic Software

Using available pumpautomation diagnosticsoftware, engineers can:

• Properly evaluate rodpumps

• Understand performanceof surface data andcalculated downholedata

• Make adjustments to rodpump installation



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Installed Rod Pump Well Data Base

Dat

e o

f L

ast

Wel

l Tes

t-

Typ

ical

Ro

d P

um

p In

form

atio

n C

olu

mn

Ob

serv

atio

ns

Co

lum

nU

sed

to

hig

hlig

ht

op

erat

ion

al o

r sp

ecif

ic i

tem

req

uir

ing

att

enti

on

or

no

tati

on

.

Well Data Base Used to Inventory and Manage all Relevant Operational Characteristics of Field Rod Pumps

This summary sheet is only to illustrate general outline.

See easy-to-read detail sheets that follow.

(7 m)

(7 m) (70 mm)

(1,915 m)

(1,864 m)

(1,937 m)

(1,875 m) (1,895 m)

(2 m)

(2 m)

(3 m)

(51 mm)

(45 mm)

(45 mm)

(2 m)

(1,749 m)

(1,849 m) (1,768 m)

(1,968 m)(2 m)

(3 m)

(45 mm)

(70 mm)

(51 mm)

Flow Station, Well, Section of Field, Surface and Subsurface Data

Flow Station

Well Field

System Information

Surface Subsurface

Pu

mp

Un

it

Man

ufa

ctu

red

Ro

tafl

ex(Y

/N)

Su

bsu

rfac

e P

um

p

Str

oke

(in

ch)

S.P

.M.

Plu

ng

er

Dia

met

er(i

nch

)

Tu

bin

g

An

cho

r D

epth

(ft

)

Pu

mp

Dep

th

(ft)

Gas

An

cho

r D

epth

(ft

)

Gra

vel

Pac

kD

epth

(ft

)

DED-01

DED-01 LM-250 Levas Rotaflex Rotaflex Y Tubing Pump 288 2.50 2.75 6234 6355 No

DED-01 LM-251 Levas C223D-26-74 Parkersburg N 74 1.40 2.00 6011 6020

DED-01 LM-254 Levas Rotaflex Rotaflex Y Tubing Pump 288 2.75 6115 6150 6217

DEF-02

No Hay

DED-03

DED-03 LG-236East

DacionC228D-200-74 Lufkin N 74 8.50 2.00 No 5737 No

DED-03 LG-258East

DacionM320D-258-120 Lufkin N 120 7.00 1.75 6065 5800 No

DED-03 LG-401 Levas C228D-200-74 Lufkin 120 4.00

DED-03 LG-407 Levas C228D-26-74 Parkersburg NInsertable

Pump74 1.75

DED-03 LG-406 Levas

DED-04

DED-04 LG-228East

DacionC228D-200-74 Lufkin N

InsertablePump

74 10.0 1.75 No No 6457



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Rod Pump Field Maintenance

Rod Size and Length, Latest Well Test Data, Fluid Level and Dynamometer Evaluation Information

Rod String Last Well Test Fluid Level and Dynocard

Ro

d x

Lo

ng

1"

Ro

d L

on

g 7

/8"

Ro

d L

on

g 3

/4"

Sta

tus

Dat

e

San

d

Res

erv

oir

BN

PD

AP

I

%A

yS

GO

R (

Imp

end

)

Dat

e

Dat

um

Flu

id L

evel

(ft)

P.I.

P.P

SI

Tu

b. P

ress

PS

I

Csg

. Pre

ss P

SI

PD

HP

PS

I

Pu

mp

Fil

l up

%

Da

te f

ield

use

d in

this

exa

mp

leto

re

cord

co

mp

letio

n o

f la

test

we

ll te

st 249 PEP S4 LM-250 105 14.1 56.0 11/1999 6355 281 2042 0 7 2042 Static

95 113 COB R4U LG-403 185 16.0 10.0 11/1999 8043 3561 788 150 1 788 Static

242 PEP S2 LM-213 276 16.0 10.0 11/1999 6150 627 1071 30 93 1071 Static

(25

mm

)

(22

mm

)

(19 m

m)

(86 m)

(191 m)

(14 MPa)

(7 MPa) (552 kPa)

(48 kPa)

(641 kPa)

(1085 m) (5 MPa) (1034 kPa) (7 kPa)

Rod Pump Field Maintenance

(7 m) (70 mm) (1,907 m)

(17 MPa) (2 m) (45 mm) (1,768 m)

Adjustment Recommendations: Pump Intake Pressure, Stroke Length and Frequency, Pump Depth, Net B/D, Efficiency, Overall

Change Recommendation

P.I.

P P

SI

Str

oke

(in

ch)

S.P

.M.

Plu

ng

er

Dia

met

er (

inch

)

Gas

An

cho

r

Pu

mp

Dep

th (

ft)

BN

PD

Eff

icie

nt

Fac

tor

Observation and Notes

Ve

rsa

tile

Co

lum

n fo

r a

ll T

ype

s o

f R

elev

ant

Rod

Pum

p R

elat

ed In

form

atio

n

288 2.5 2.75 N/N 6355 105 1.69

Connected but the motor does no receive power.

1.24

N/N 1.16

2431 74 6 1.75 N/N 5000 216 1.03



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Rod Pump Controllers


Learning Objectives


Demonstrate how the use of modern instrumentation “smartwell” systems to control pump operation, gather data, andmanage pump functions results in optimum pump performanceand minimized costs



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Module Contents









Summary

Pump Off Controllers

Most common rod pump problem.

Pump overdesigned vs. well inflow.

Condition caused by incompletefilling of the fluid barrel on theupstroke which results in thedownstroke movement of pumphitting the partially filled barrel.

Detrimental to rods, pump, tubingand surface equipment.

Options include reducing pumpSPM, stroke length, install a smallerpump or a combination of the above.

Pump off controllers (POCs) turn offthe pump when reservoir inflow isinsufficient and fluid pound ensues.

Fluid Pound



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Modern Pump Off Controller Systems

Modern microprocessor based multifunction systems:• Detect and control fluid pound• Adjust motor speed• Determine pump fill percentage• Acquire load / position data• Calculate gross fluid production• Manage set points for peak torque• Set and manage load limits• Detect, manage, and shut down on overload conditions• Other monitoring variables



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Summary


Learning Objectives


Develop engineering and operating skills to successfully design,properly set up, maintain, and provide overall service forimplementing and applying reciprocating rod pump artificial lifttechnology

Work several rod pump design exercises to assess maximumand minimum pump load, minimum and maximum rod stress,motor selection, strokes per minute, stroke length, and relatedoverall rod pump design parameter selection



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Module Contents









Summary

Rod Pump Summary – Advantages

Rod pumps generate low bottomhole operatingpressures [200' (61 m) of head over the pump or~200 psi (1,379 kPa) FBHP].

Reliable and flexible.

High salvage value for surface equipment (rarelybought new).

Low operating costs if set up properly and operatedproperly.

Simple to operate and understand (design ischallenging).

Less sensitive to pump-off (i.e., reducing fluid level tobelow pump) than other artificial lift types (e.g.,submersible pumps).

Ro

d P

um

p A

dva

nta

ges

Ro

d P

um

p A

dva

nta

ges



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Rod Pump Summary – Disadvantages

Production rates generally lower than other artificiallift types.

Production rate capability decreases rapidly withpump depth.

System not compatible with subsurface safety valve(SSSV).

Cannot be used on wells capable of flow.

Rods prevent measurement of flowing and staticpressures (but with proper tools to measure fluidlevel, can estimate both).

Gas in pump reduces efficiency dramatically.

Very large surface equipment.

Rod / tubing wear problems in deviated wells.

Ro

d P

um

p D

isad

van

tag

esR

od

Pu

mp

Dis

adva

nta

ges

Exercise: Rod Pump Design Variables

Work the rod pump design exercises using the Echometersoftware program provided.

• Initial data assumption variables are provided (well depth, strokelength, anchored tubing diameter, pump diameter, etc.).

• Evaluate the chosen pump by following the recommendedsequential steps in the exercise.

In the second synchronous review session,the module instructor will work / demonstratea complete design of several rod pumpconfigurations (surface unit, rod string,downhole pump, motor HP, and relatedparameters).

Exercises



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Exercise: Rod Pump Design Variables

1. Enter strokes per minuteand pump plungerdiameter

2. Enter rod string type

3. Enter rod grade material

4. Enter pumping unit andstroke length

Execute Program and Check for:

Production Desired

Yes – proceed below No – revise design data

Rod Overload

Gear Box Overload

Yes – revise design data No – proceed below

Yes – revise design data No – pump design complete

Rod Pump Design Method



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