Rod PumpSystem Performance

And Evaluation MELEIHA OIL FILD – AGIBA PETROLEUM COMPANY

AgendaSystem performance

A. Failure Analysis

(Problem Nature – Reasons – AGIBA Application)

B. Troubleshooting

(Physical Indicators – Common techniques – Common mistakes )

Gas InterferencePROBLEM NATURE

• Gas separated and accumulated inside the pump reducing the volumetric efficiency and in the worst case the well stops pumping due to gas lock.

PROBLEM REASONS

• High GOR or foamy fluids .

• Poor gas venting while production.

Real Gas Interference card from Well S-66

Gas interfernce..cont.Remedial Action

- Increasing the compression ratio by the following Modifications to Standard Pumps:-

• Longer stroke length, close valve spacing & spaced low (w/o tagging) at well site

• High comp. standing valve cage

- Improve gas venting through annulus .

- Install pump below perforations to allow for gravity separation

- Install gas anchor ( separator ) .

- Use vsp (variable slippage pump ) .

GAS ANCHOR ( SEPARATOR ) VARIABLE SLIPPAGE PUMP

• In Agiba applications some of the NE wells, SE, Zarif, Faras and Ramel fields are the highest gas to oil ratio (GOR) wells (over 300 SCF/STB). In 1988 Agiba ran poor-poy type gas separator tests for two of the SE wells. They did not show any significant improvements and this technique had some limitations:1. It was not effective for wells producing over 300 BOPD.2. It Impedes possible wire-line operations in the well in which it is used

Pump Intake setting below perforations

• Seating the pump intake below the perforations is the mostefficient technique if the well conditions allow it.AGIBA applies the process for some of the Meleiha wells (M-8,SE-6) as a trials and it was proved to be very efficient most of theFaras, Raml and Zarif field wells.

Application of the technique created the following advantages:

• Increased pump submergance which resulted in moreproduction.• Created a natural gas-separation, which improved the pumpsmechanical performance.

limitations to this technique:Not recommended for sandy wells where pump-sticking problem arise.

Fluid poundPROBLEM NATURE :

Incomplete pump fillage creates a hammering effect for S.R.

PROBLEM REASONS :

• Insufficient pump intake pressure .

• pump intake restriction .

CAUSES SEVERE PROBLEMS LIKE :

• Pumping unit base vibration ( loosens the bolts ).

• Gear box teeth damage .

• S.R. Premature fatigue failure S.R. Premature fatigue failure .

• Rod unscrew from bottom .

• Rod buckling and excessive TBG. Wear

Fluid pound..cont’

Remedial Action

• Re-optimize the pumping parameters ( S.L. , SPM & P.S. ) .

• Use pump off controller to match pumping rate with the Actual well productivity .

• check pump intake for restriction ( this could be Considered in case of pounding at higher dynamic level) .

• increase pump submergence if possible .

Fluid pound..cont’In Agiba Applications, The reservoir is a depletion drive type and the fast decline in reservoirpressure was affecting the pump intake pressure. Therefore, the gas and fluid pounding problembecame a serious issue and the decrease in the dynamic fluid level consequently increased thepeak polished rod load due to increasing the net lift.

Split traveling valve cage from fluid pound

Fractured nickel-carbide standing valve seat from fluid pound

Scale depositionPROBLEM NATURE AND REASONS

• It was observed that scale formation problems started to appear in some of the Meleiha and Raml field wells. Chemical analysis showed that it was the calcium carbonate (CaCO3) type. Such scale precipitates in the upper part of the tubing (surface down to about 300 ft). Presence of scale restricted operations during pulling and running of the subsurface pump. In some cases it created stuck pumps and then a work over was needed.

• The reasons for this problem are as follows: -

1. Pressure drop at the wellhead (below 100 psi).

2. High formation water production.

3. High temperature (over 120 F).

Scale deposition..cont’• To prevent scale formation inside the well, it was found that increasing the wellhead pressure to 150 psi would significantly improve the situation.

STUCK STANDING VALVE DUE TO SCALE

Sucker Rod Failures..cont’A – TENSILE FAILURE :• It appears as a bottle neck shape due to rod elongation when using improper rod type or creates excessive tension to free stuck pump ,(actual applied loads tension to free stuck pump exceeds the allowable loads ) .B–CORROSION FAILURE : • The rod is parted due to area reduction as a result of corrosion ( chemical reaction between steel and CO2 , H2S OR ACID .C – FATIGUE ( MECHANICAL ) FAILURE :• It originates from a local increase in stress as small, progressive stress cracks that advance, upon each applied load, with the action of fluctuating or cyclic stresses to rupture, or final shear tear. SUCH TYPE IS CONSIDERED THE MOST COMMON TYPE WORLD WIDE .Caused by Improper make-up, severe fluid pounding , manufacturer defects ,using old rods without inspection , pump tagging down .

Sucker Rod Failures..cont’D - ROD BUCKLING TENDENCY :• Buckling tendency happens due to compression loads in the down stroke (the rod should be kept under tension in all conditions ).PROBLEMS RELATED TO BUCKLING :• Excessive rod and tubing wear .• sucker rod failure or unscrew .• valve rod and valve rod guide damage .Reasons :• severe fluid pounding .• excessive rod speed ( exceeds free fall speed ) .• heavy viscous oil .• improper rod string design .• pump tagging .

Sucker Rod Failures..cont’ROD BUCKLING TROUBLESHOOTING :• Eliminate pounding and optimize speed specially in heavy viscous wells• Use sinker & stabilizer bars to centralize rods and keep in tension .• Never keep pump strongly tagging down .

CORROSION TROUBLESHOOTING :• Use corrosion resistant rod type .• use corrosion inhibitor

MAX TENSILE TROUBLESHOOTING :• Better rod type selection during the initial design .• Never exceed the allowable rod load rating during trials to free stuck pump .

FATIGUE TROUBLESHOOTING :• Re-optimize the well pumping parameters to minimize fluid pounding .

Sucker Rod Failures..cont’

TENSILE FAILURE FATIGUE

Valve rod guide damage Due to buckling

Heavy Oil• Characteristics of Aghar Field Heavy Oil

- API 10-17

• PCP Vs. S/R System in Aghar Field

- Limited ability to increase the PCP parameters

- Limited well accessibility

• Applying S/R Systems in heavy oil wells

- Small Pumping Units

- Slow pumping rate Real Viscous oil problem from Well AG 4-13

Sand ProductionPROBLEM NATURE

• When Producing Sand Up through your Production Tubing, Separation Will occur. The Heavier, MoreAbrasive Sand, Will Settle Back On Top Of The Rod Pump. The Smaller, Less Abrasive Sand Will StaySuspended, And Be Lifted To The Surface. The heavier sand will brake up to small pieces and be carriedbetween the plunger and barrel.

PROBLEM REASON

• The sand particles will work their way between the Barrel and the plunger, causing abrasion cuts ,commonly known as “sand cutting”.

• Sand Friction causes rod buckling resulting in failures.

Sand Production..cont’• Two origins in AGIBA

- Formation sands/fines

- Hydraulic fractured Wells sands / propants

• Effect of sand on the total production system

- Sand friction cause rod buckling

- Abrasion/wear for the plunger “Sand Cut”

Wear of Plunger caused by sand production

Sand Cuts

Sand Production..cont’Remedial Actions

• Using Top Hold Down pumps

• High Clearance Pumps

• Sand screens

- Through TBG Screens

- TBG Screens

• Re-completion

Stuck pumps In AGIBA application stuck pumps which existedonly in the Bottom Hold-Down type. This BHDcreates the possibility of sand & debrisaccumulating in the dead area between thepump and the tubing wall.

Such problems was overcome by introducing theTop Hold-Down pump instead of bottom holddown.

Tubing WearPROBLEM NATURE

Tubing failures had longitudinal cracks with an average length of 10 ft. and all the cracks were in the lower part of the tubing ( up to 500 ft above the pump seating nipple). This tubing interval was located against the sinker bar portion of the sucker rod string.

• IT IS CONSIDERED AS ONE OF THE COMMON PROBLEMS OF S.R. System world-wide .

TBG. Wear due to rod buckling

TBG. Wear ..cont’ PROBLEM REASONS :

• Rod buckling (high speed , insuffecient sinker bar , fluid pounding , pump tagging down ) .

• Tubing buckling (unanchored tubing or apply insufficient tension ) .

• Use sucker rod system in crooked holes .

• Free water production (represents the main critical reason Since it increases mutual friction between rods and tubing ) .

• Presence of corrosive fluids ( enhances the erosion corrosion effect )

TBG. Wear ..cont’ HOW TO MINIMIZE TUBING WEARS AND CRACKS :

• Eliminate all reasons of rod buckling .

• Apply proper tension for tbg. String ( use KTH hanger ) .

• Use rod guides or wheel guides to centralize rods inside tubing .

• Use anti-friction couplings and blast joints in the hot spots .

• Apply corrosion inhibition programs .

• Minimize pumping speed .

WELLNO. OF W/O DUE

TO TBG LEAK per year

M-29 3

M-42 3

A-6 3

A-46 3

NE-36 3

M-43 3

M-57 3

A-4 5

NE-14 3

NE-25 3

SE-4 3

E-1X 3

N.NADA-8 3

FALAK-11 3

M-14 3

A-41 3

WELLS FREQUENTLY SUFFERED FROM TBG LEAK

NE-32 2

NE-43 2

M-SW-2 2

SE-20 2

FALAK-7 2

A-37 2

Z-27 2

M-33 2

M-50 4

M-18 4

M-34 4

M-37 4

M-47 4

M-52 3

A-25 3

Z-15 3

M-49 3

• The main problem lead to workover jobs in AGIBA is the tubing leak , which appears inthe form of longitudinal cracks as 2 ft length × 2cm width, caused by contineous frictionbetween sucker rod and internal tubing wall , especially at the last ten joints ( 300 ft )right above the pump.

Rod Guides

Spiral metal guides were tested in AGIBA fields. The experience proved that it was not an effective solution for this condition due to the following difficulties:a. It required fixed regular schedules for round trips to replace the worn-out guides.b. The installing of rod guides created much more friction, which increased the loads and stresses in the sucker rod string and the possibility of rod failure.Due to high loads, there was no way to increase pumping parameters in order to increase production.

- Valve rod guide worn-outDue to buckling

- Metal to Metal contact- High friction

Hollow PumpWELL

PERIOD BETWEEN LAST W/O & FIRST TBG LEAK

M-14 8 MONTHS

M-37 1 YEAR

M-47 7 MONTHS

A-4 11 MONTHS

A-5 6 MONTHS

A-34 9 MONTHS

FIELD TRIALS (HOLLOW PUMP)

Hollow sucker rod has hole in the middle The smaller passage and the faster flow velocity can avoid the sand deposit efficiently while use hollow sucker rod in the sand well.

WELL Rate W/CPERIOD BETWEEN LAST W/O & FIRST TBG LEAK

E - 1X 215 45 9 MONTHS

M - 37 80 55 6 MONTHS

- Using of roller guide or wheel guide , to eliminate direct contact between sucker rods and internal tubing wall.

- Applying of a KTH flange gives more tension for tubing with slips to prevent tubing buckling.

Rod PumpTrouble Shooting

Physical Trouble Shooting Indicators- Pressure Gages

- Hot Flow Lines

- Hot Polished Rod Load

- Sounds at the Well

- Equipment Vibrations

- Fluid on the Ground

- Ground Shakes

Well Head Temperature As A Relation Of Production Rate (GOR From Zero Up To 100 Scf/Stb)

Well head temperature, oF

Pro

du

cti

on

ra

te, b

pd

Zero water cut

Zero up to % water cut

up to % water cut

up to % water cut

common Techniques for Trouble Shooting- Has Well’s Production Changed?

- Can the Pump Pressure up the Tubing?

- Is the Pumping Unit Running?

- Is there a noticeable Leak?

- Is fluid going into the tank?

- Has the Fluid Level Changed?

Not Recommended- Why are not we tagging?

- Put on hand and Pump 24 hrs/day.

- Increase SPM in Order to maintain Production.

- Increase SPM because there is a Fluid Level Above the Pump.

- Pull the Well, because no Fluid in the Tank.