Session #1 Virtual Instructor Led COPYRIGHT

Session #1 Virtual Instructor Led

Reciprocating Rod PumpFundamentals

Module Contents

Reciprocating Rod Pump Components and Operational Principles

Pump Size / Pump Design

Rod Pump Surface Unit

Rod Pump Rod String

Rod Pump Downhole Pump

Dynamometer Analysis

Failures and Maintenance

Controllers

Summary

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

© PetroSkills, LLC., 2016. All rights reserved._____________________________________________________________________________________________

1

COPYRIGHT

Module Contents




Rod Pump Rod String




Controllers

Summary

Module Contents




Rod Pump Rod String




Controllers

Summary

Instructor Virtual Led Session #1 ═════════════════════════════════════════════════════════════════════════

2_____________________________________________________________________________________________

© PetroSkills, LLC., 2016. All rights reserved.

COPYRIGHT

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

Group 2 Well Characteristics

Wells less than 4000 ft (1220 m) deep

AND

Have a pump diameter greater than 2 inches (5.08 cm)


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

OR

Wells less than 4000 ft and a pump diameter less than equal to 2 inches (5.08 cm)

Group 1 and Group 2 Rod Pump Wells

Each of the above groups has unique features



3

COPYRIGHT


Fluid Inertiaeffects in large volume shallow

wells (lesser rod stretch to absorb load “shock”) is the most important diagnostic

consideration.

As a result, larger forces are required to accelerate fluid

loads beginning the upstroke which complicates rod pump

well diagnosis.


Road Loading / Rod Stretcheffects in deeper wells is the

most important diagnostic consideration.

For shallower wells, minimal fluid inertia effects and minimal

rod stretch effects aids rod pump well diagnosis.

Group 1 and Group 2 Rod Pump Wells – Main Differences

Group 1 Well Features (> 4000 ft or < 4000 ft & 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 many factors:

• 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 is expected 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 pump performance

(1220 m) (5 cm)


4_____________________________________________________________________________________________


COPYRIGHT

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” effect of the rods

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

to analyze pump performance

(1220 m) (5 cm)

Analyzing Group 1 and Group 2 Rod Pump Wells

Dynamometer data and software programs are the primary diagnostic tools for modern rod pump wells

Surface diagnostic data measuring the load on the rod string as a function of position throughout the upstroke / downstroke rod pump cycle is used to predict downhole loads on the pump

Modern diagnostic analysis computer programs provide quantitative analysis to distinguish between mechanical pump problems (e.g., leaking or worn pump) and fluid issues (gas, low productivity zones, etc.)



5

COPYRIGHT


Question / Discussion:

Is the function of the dynamometer clear?



Is the function of the dynamometer clear?

Rod pump animations follow...


6_____________________________________________________________________________________________


COPYRIGHT

Module Contents




Rod Pump Rod String




Controllers

Summary

PBHP

Fluid Level

Gas

Pt

Pc

Rod Pump Design Starts with Inflow (Rate) Determination

Engineers use acoustic surveys to determine bottomhole pressures.

A remotely fired gas gun with a precision pressure transducer to measure casing pressure change as an acoustic signal measures the distance h' to the fluid level.

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

from: Echometer

Pump

Oil + Gas

Liquid



7

COPYRIGHT

Knowing h, then:

h x fluid gradient = PBHP

PBHP - for both flowing and shut-in conditions

Knowing the distance to the liquid level for both flowing and shut in conditions allows engineers to determine the height of 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

Knowing h, then:

h x fluid gradient = PBHP

PBHP - for both flowing and shut-in conditions

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


Is It clear how well fluid inflow will determine pump capacity sizing?


8_____________________________________________________________________________________________


COPYRIGHT

Module Contents




Rod Pump Rod String




Controllers

Summary

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



9

COPYRIGHT

Rod Pump Surface Unit Types

Rod Pump Surface Unit Types


10_____________________________________________________________________________________________


COPYRIGHT

Conventional Rod Pump Units


If a conventional unit can be operated in both a clockwise and counterclockwise direction, and if the gear box routinely suffers wear on the gears, assume that well #123 has been operating in the clockwise direction for several years.

What might be the reason for reversing the unit to operate in the counterclockwise direction?

Wellhead

Long stroke polished rod

Hydraulic cylinder actuator

RotoflexTM Unit

Long Stroke Polished Rod Pump

The Rotaflex has two sprockets connected by a large chain

On the front of the unit is a large, reinforced steel belt

• This connects to the polished rod in the well

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



11

COPYRIGHT

Wellhead

Long stroke polished rod

Hydraulic cylinder actuator

RotoflexTM Unit

Long Stroke Polished Rod Pump


What would the long stroke length of a Rotolex unit provide?

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


12_____________________________________________________________________________________________


COPYRIGHT

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 (7.6 m) require large, long pumps

Hydraulic Unit• Higher maintenance costs

• Complex hydraulics, therefore breakdown frequency

Disad

vantag

esD

isadvan

tages

BOTTOM OF DOWNSTROKE

TOP OF UPSTROKE

Rod Pump Operating

At the top of the upstroke, the unit has lifted well fluids one stroke length and the rods to the surface.

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

One half rod pump cycle illustrated



13

COPYRIGHT

On the downstroke, the gearbox lifts the counterweight with the help of the rod load (to get the counterweight ready to help again on the upstroke).

On the upstroke, the counterweight releases energy to the gearbox and helps the gearbox by falling.

Rod Pump Operating

TOP OF UPSTROKE

BOTTOM OF DOWNSTROKE

Mark II Unit Crank

Conventional Unit Crank

Mark II Unit Rod Pump Offset Crank Angle

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.

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.


14_____________________________________________________________________________________________


COPYRIGHT

C-228D-246-86

See API Specification 11E

Rod Pump Surface Unit API Designation

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

A “letter” indicating pump type is often placed in

front of the surface unit naming designation

168”(4.3 m)

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)



15

COPYRIGHT

Example: Rod Pump Surface Unit Identification

X-XXX-XXX-XXX UnitX-XXX-XXX-XXX 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


Could you identify a rod pump based upon its API 11E spec ?

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 performed by a strain gauge tool called a dynamometer.


16_____________________________________________________________________________________________


COPYRIGHT

Rod Pump Data Gathering and Design

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

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

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

Load vs. Position of Walking Beam and Rods

Rod Pump Idealized Dynamometer Card Analysis

Trav. 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



17

COPYRIGHT

Sheaves and Gear Box

Typically beam pump motors are running 1200 or 1800 RPM (Revolutions Per Minute)

Need a method to reduce speed to get down to approximately 10 SPM (Strokes Per Minute)

Use ratio of sheaves and gearbox

Gear Reducer Box Illustration

Case Head Removed For Lubrication Maintenance

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


18_____________________________________________________________________________________________


COPYRIGHT

1170x 12" / 47" = 298.7 RPM(119 cm / 31 cm)

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 Sheave47" diameter (119 cm)

298.7 RPM30.12 GB Ratio

= 9.92 SPM

Motor RPM1170 RPM

Motor Sheave12" diameter (31 cm)

Gear Box Ratio30.12

STEP (1)

STEP (2)

STEP (3)

Rod Pump Strokes Per Minute Exercise

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

• A rod pump has a motor sheave of 10" (25.4 cm) O.D.

• The gear-box sheave is 34" (86.4 cm) O.D.

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

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



19

COPYRIGHT

Rod Pump Strokes Per Minute Exercise

10" / 34" =(25.4 cm / 86.4 cm) 10" / 34" =(25.4 cm / 86.4 cm)

RPM x 0.294 =500 x 0.294 =

147.1 RPM

RPM x 0.294 =500 x 0.294 =

147.1 RPM

147.1 RPB / 30 = 4.9 SPM

147.1 RPB / 30 = 4.9 SPM

0.294

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

• A rod pump has a motor sheave of 10" (25.4 cm) O.D.

• The gear-box sheave is 34" (86.4 cm) O.D.

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

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

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


20_____________________________________________________________________________________________


COPYRIGHT

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

Wrist Pin

Pitman Arms

Rod Pump Crankshaft / Counterweight

Counterweight

Gear Box

Crank Arm

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



21

COPYRIGHT

Module Contents




Rod Pump Rod String




Controllers

Summary

Major Rod Pump System Components

Surface pumping unit and prime mover

Rods run from surface to downhole pump• Rods are also referred to as “sucker rods”

Downhole pump


22_____________________________________________________________________________________________


COPYRIGHT

The Rod String

The Rod String


Have you been on site when rod pump rods were being pulled... or if tubing also was worn and also required replacement?



23

COPYRIGHT

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

6 / 8

API 86 Rod String

Rods equally stressed

Rods designed with equal fatigue failure tendency

8 / 8Tapered String

The Rod String (Rod Pump Sucker Rods)

7 / 8

46.2%1.5" Pump –(3.8 cm)

26.8%, 27%,

Equal Stress

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 type and corrosive environment of the wells where they will be used.


24_____________________________________________________________________________________________


COPYRIGHT

Stress Strain Curve

Rod Pump Rod Design

Rod Stress / Strain Curve • Sucker Rods should operate

in the linear portion of the stress vs. stain curve and never undergo permanent deformation.

• Rod Fatigue is, however, the main design consideration for continuous operation.

• Per API standard, when the difference between (range of) the maximum and minimum actual stress on rod string is great, the allowable rod stress is decreased. 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)

Construction of Modified Goodman Diagram

Rod Pump Rod Design

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

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

T

T/1.75

T/4SA

Sm

T

T



25

COPYRIGHT

Rod Pump Rod Design

Service Factors (SF) de-rate the allowable 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

Rod Pump Rod Design

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


What would be the effect of API changing the Modified Goodman variable as highlighted below?


26_____________________________________________________________________________________________


COPYRIGHT

Rods Design Example: Get Surface Rod Loads from Dyno Card

Rod Area is .601 in2 (3.88 cm2)

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 CardRod Diameter is .875 in

(2.22 cm)

(8,165)

(9,072)

(7,257)

(6,350)

(5,443)

(4,536)

(3,629)

(2,722)

(1,814)

(907)

(kg

)

Smin = 15,141 psi(104 Mpa)

Sucker Rod Design – Modified Goodman Diagram

T/1.75

T/4

0

115,000 psi (7,929 Mpa)

Pk Stress = 29,768 psi(205 MPa)

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

= 37,267 psi(257 Mpa)

37,267 – 15,141

29,768 – 15,141

= 66%

Rod Loading

205 -104257 -104

S.F. = 1.0



27

COPYRIGHT

Smin = 15,141 psi(104 Mpa)

= 29,814 psi

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)

Sucker Rods: Co-Rod

From: Weatherford

Ad

van

tag

es

Disad

vantag

es

• cost possibly up to five times higher than comparable conventional rod

• service rig and welding unit must be available in the area for servicing

• connection to polished rod and pull rod 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


28_____________________________________________________________________________________________


COPYRIGHT

Sucker Rods: Co-Rod

From: Weatherford

Ad

van

tag

esQuestion / Discussion:

Do you know if your organization has evaluated the use of COROD strings?

Module Contents




Rod Pump Rod String




Controllers

Summary



29

COPYRIGHT

Exercise: Rod Pump Design Variables

Assignments:

1. Review the videos and animations for rod pump wells.

2. Work the rod design exercises using the Modified Goodman method.

End of Virtual Session #1


30_____________________________________________________________________________________________


COPYRIGHT

Session #1 Virtual Instructor Led COPYRIGHT

Documents

Transcript of Session #1 Virtual Instructor Led COPYRIGHT