where is the damage? how does it affect production? · pdf file• where is the damage?...
TRANSCRIPT
Formation Damage – Effects and Overview
• Where is the damage?
• How does it affect production?
3/14/2009 1George E. King Engineering
GEKEngineering.com
Impact of Damage on Production
• Look at Effect of Damage
• Type of Damage
• Severity of Plugging
• Depth of Damage
• Ability to Prevent/Remove/By-Pass
3/14/2009 2George E. King Engineering
GEKEngineering.com
3/14/2009 3George E. King Engineering
GEKEngineering.com
Horizontal Well Formation Damage Theories
Zone of Invasion - Homogeneous Case
50423009
Is damage evenly spread out along the well path or does it go down the highest permeability streaks?
3/14/2009 4George E. King Engineering
GEKEngineering.com
Horizontal Well Formation Damage TheoriesZone of Invasion - Heterogeneous Case
504230103/14/2009 5
George E. King Engineering GEKEngineering.com
Observations on Damage
1. Shallow damage is the most common and makes the biggest impact on production.
2. It may take significant damage to create large drops in production
3. The problem, however, is that the highest permeability zones are the easiest to damage, and that can have a major impact on productivity.
3/14/2009 6George E. King Engineering
GEKEngineering.com
Pressure Distribution Around a 200 md Oil Well
2000
2100
2200
2300
2400
2500
2600
2700
2800
0 200 400 600 800 1000 1200
Radial Distance, ft
Pres
sure
, psi
World Oil, Modern Sandface Completion Practices, 2003
The pressure drop around an unfractured wellbore shows the importance of the near wellbore on inflow. If this area is significant damaged, the effect is immediately noticeable.
3/14/2009 7George E. King Engineering
GEKEngineering.com
Effect of Depth and Extent of Damage on Production
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3
Radial Extent of Damage, m
% o
f orig
inal
Flo
w
80% Damage90% Damage95% Damage
1. The most noticeable damage impacts the the well in the first 30 cm or 12 inches of the formation.
3/14/2009 8George E. King Engineering
GEKEngineering.com
Effect of Damage Layer Thickness
0.001
0.01
0.1
1
0.01 0.1 1 10
Damaged Perm, % of initial
Prod
uctiv
ity
Rat
io
0.01" thick0.05" thick0.1" thick1" thick
2. The effect of the damage thickness compared with the amount of damage (as a percent of initial permeability). Only the most severe damage has a significant effect in a thin layer. (Darcy law beds-in-series calculation)
3/14/2009 9George E. King Engineering
GEKEngineering.com
Productivity Loss From Formation Damage
0.250.3
0.350.4
0.450.5
0.550.6
0.650.7
0.750.8
0.850.9
0.951
0 2 4 6 8 10
Depth of Damaged Zone, inches
Prod
uctiv
ity a
s a
Frac
tion
of
Und
amag
ed P
rod.
Kd/Ki = 0.5Kd/Ki = 0.2Kd/Ki = 0.1Kd/Ki = 0.05Kd/Ki = 0.02
World Oil, Modern Sandface Completion
2. (continued) As the damage layer thickens and becomes more severe, the impact on production builds quickly.
3/14/2009 10George E. King Engineering
GEKEngineering.com
3. Highest permeability zones are easiest to damage:Pore Size vs. Permeability
y = 1.3661x2.4865
R2 = 0.982
0
50
100
150
200
250
300
350
0 1 2 3 4 5 6 7 8 9 10
mean hydraulic radius (µm)
perm
eabi
lity
(m
SDA-01 Balakhany X (SP2) Hg permeability mDSDA-01 Fasila B (SP3) Hg permeability mDSDA-02 Balakhany VIIIC Hg permeability mDSDA-02 Fasila D (SP4) Hg permeability mDK mDPower (K mD)
MI for BP SD field
Large connected pores and natural fractures dominate the permeability of a formation.
The size of particles that can cause damage in these larger pores is larger than 1/3rd and smaller than 1/7th. For a 8 micron pore, the small size would be 1 micron and less.
3/14/2009 11George E. King Engineering
GEKEngineering.com
The Effect of Damage on Production
Rate = (∆P x k x h) / (141.2 µo βo s)
Where:∆P = differential pressure (drawdown due to skin)
k = reservoir permeability, mdh = height of zone, ftµo = viscosity, cpβo = reservoir vol factors = skin factor
What are the variables that can be improved, modified or impacted in a positive way?3/14/2009 12
George E. King Engineering GEKEngineering.com
Productivity and Skin Factor
• Q1/Qo = 7/(7+s)
Where:
Q1 = productivity of zone w/ skin, bpd
Qo = initial productivity of zone, bpd
s = skin factor, dimensionless
Just an estimation, but not too far off between skin numbers of zero and about 15.
3/14/2009 13George E. King Engineering
GEKEngineering.com
Productivity Ratio vs. Skin Factor
0
50
100
150
200
250
-5 5 15 25 35 45 55
Skin Factor
Prod
uctiv
ity F
acto
r, %
Range of Skin Factors Associated with Frac Pack
Range of Skin Factors Associated with Cased Hole Gravel Pack Completions
A better presentation of the damage from increasing skin factor. Skin only has an impact if the well can really produce the higher rate and the facilities can process it.
3/14/2009 14George E. King Engineering
GEKEngineering.com
Example
• Productivity for skins of -1, 5, 10 and 50 in a well with a undamaged (s=0) production capacity of 1000 bpd
• s = -1, Q1 = 1166 bpd• s = 5, Q1 = 583 bpd• s = 10, Q1 = 412 bpd
• The best stimulation results are usually for damage removal and damage by-pass.
3/14/2009 15George E. King Engineering
GEKEngineering.com
Another way of stating damage - Damage in a horizontal well – increasing skin makes the well behave like the drilled lateral was much shorter.
3/14/2009 16George E. King Engineering
GEKEngineering.com
Damage Causes
• Obstructions in the natural flow path in the reservoir.
• “Pseudo” damage such as turbulence - very real effect, but no visible obstructions
• “Structural” damage from depletion – matrix compression, etc.
3/14/2009 17George E. King Engineering
GEKEngineering.com
Flow Path Obstructions
• Scale, paraffin, asphaltenes, salt, etc.,• Perforations – 12 spf w/ 0.75” / 1.9 cm holes only
opens 2% of the casing wall.• Tubing too small - too much friction• Any fluid column in the well, even a flowing fluid
column holds a backpressure on the well:– Salt water = 0.46 psi/ft– Dead oil = 0.36 psi/ft– Gas lifted oil = 0.26 psi/ft– Gas = 0.1 psi/ft (highly variable with pressure)
3/14/2009 18George E. King Engineering
GEKEngineering.com
“Pseudo” Damage
• Turbulence– high rate wells– gas zones most affected
• Affected areas:– perfs (too few, too small)– Near wellbore (tortuosity)– fracture (conductivity too low)– tubing (tubing too small, too rough)– surface (debottle necking needed)
3/14/2009 19George E. King Engineering
GEKEngineering.com
“Structural” Damage
• Tubular Deposits– scale
– paraffin
– asphaltenes
– salt
– solids (fill)
– corrosion products
3/14/2009 20George E. King Engineering
GEKEngineering.com
Perforation Damage
• debris from perforating• sand in perf tunnel - mixing?• mud particles• particles in injected fluids• pressure drop induced deposits
– scales– asphaltenes– paraffins
3/14/2009 21George E. King Engineering
GEKEngineering.com
Near Well Damage
• in-depth plugging by injected particles
• migrating fines
• water swellable clays
• water blocks, water sat. re-establishment
• polymer damage
• wetting by surfactants
• relative permeability problems
• matrix structure collapse
3/14/2009 22George E. King Engineering
GEKEngineering.com
Deeper Damage
• water blocks
• formation matrix structure collapse
• natural fracture closing
3/14/2009 23George E. King Engineering
GEKEngineering.com
Other Common Damages
• fines migration (increasing skin)
• water blocks
• scale
• emulsions
• paraffin and asphaltenes
• turbulence – rate dependent skin
• perf debris
• Initial damage from mud and DIF’s3/14/2009 24
George E. King Engineering GEKEngineering.com
Skin Components and Determination
• Total Skins (s’) = So + Stp + D Q
Where:
So = laminar skin
Stp = 2-phase skin
D = rate dependent skin
Q = rate
3/14/2009 25George E. King Engineering
GEKEngineering.com
Skin Components and Determination
• Multi-rate tests => So, Stp, D
• B/U Test => total skin, k
• 2 B/U Tests => So, D, k
3/14/2009 26George E. King Engineering
GEKEngineering.com
Cleaning Damage
• Most damage is removed by simple clean-up flow.
• How much drawdown?
• How long to flow it?
• How soon to flow it?
• To do it?
3/14/2009 27George E. King Engineering
GEKEngineering.com
Root Causes of Residual Damage After Clean-up Flow….
• High perm formations less affected?– Major damage removers:
• Flow Rate per unit area,
• Flow Volume per unit area,
• Pressure pulse?
• Drawdown per unit area – a control?
3/14/2009 28George E. King Engineering
GEKEngineering.com
First Problem
We don’t understand cleanup by flow…
It’s a matter of flow rate and volume through a given area.
3/14/2009 29George E. King Engineering
GEKEngineering.com
For the same pay thickness, a horizontal well or a fractured well may contact 100’s of times more pay zone areathan a vertical well.
Now, think about the set drawdown – say 500 psi - per unit area, the velocity generated, and the total volume per area.
A 10 ft pay in a vertical well w/ 6” diameter yields contact area of 16 ft2
A 1000 ft pay in a horizontal well w/ 6” diam. yields contact area of 1600 ft2
Clean-up flow is “diluted” by the length of interval open at once for cleanout.
3/14/2009 30George E. King Engineering
GEKEngineering.com
Which has the potential of cleaning up faster and more completely?
Vertical well - 500 psi dd and an inflow of 100 bbl/day/ft spread out over just 16 ft2 will generate a clean-up flow of 110 gal per hour per ft.
Horiz. Well – assume 5x more than vertical flow (typical) – would generate 5000 bpd, but spread over 1600 ft2 – and release a clean-up flow of only 3 gal per hour per ft.
1000 bpd
5000 bpd
3/14/2009 31George E. King Engineering
GEKEngineering.com
Second Problem
• We don’t understand damage.– How it got there
– How it is removed.
– How to prevent it.
– What operations put the well’s productivity at risk.
3/14/2009 32George E. King Engineering
GEKEngineering.com
Industry Frac Pack Oil & Gas Well Performance(permeability-thickness vs. skin)
-5
0
5
10
15
20
25
30
35
40
100 1,000 10,000 100,000 1,000,000
Permeability Thickness (md-ft)
Ski
n
Heidrun Gp
Harding Appraisal GP
MC109 Frac-Enzyme - Oil
Pompano - Oil
Mars FP - Oil
Mars HRWP
Marathon Data
Oryx HRWF- HI 379 - Oil & Gas
Elf Hylia X/L + HEC Tail - Oil
Ew ing Bank FP- Oil
DD FF EE
Some examples of GOM skins versus md-ftNote the increasing skin in higher conductivity wells – why? It should be easier to remove damage in higher perm formations. The key here is that turbulent (non-darcy or non mechanical) skins are nearly always higher in high capacity wells – especially gas.
There are many damage mechanisms, but few are permanent if we learn how to remove them.
3/14/2009 33George E. King Engineering
GEKEngineering.com
Fluid Loss Rate from Pre Workover PI - Alaska
0
500
1000
1500
2000
2500
0 2 4 6 8 10
PI, bbls/day/psi
Dai
ly L
oss,
bbl
s
SPE 26042
Cleanup examples from Alaska wells – high losses into high PI wells, but…….
3/14/2009 34George E. King Engineering
GEKEngineering.com
% change in PI
-100
-80
-60
-40
-20
0
20
40
60
0 2000 4000 6000 8000 10000 12000
Total Fluid Loss, bbls
% c
hang
e in
PI o
n W
orko
ver
…there was actually little correlation with amount lost.
3/14/2009 35George E. King Engineering
GEKEngineering.com
PI Change, Perfs Not Protected
-100
-80
-60
-40
-20
0
20
40
1 3 5 7 9 11 13 15
% C
hang
e in
PI
Short Term PI ChangeLong Term PI Change
0.3 0.5 1.1 2.1 3.1 6 18.9
PI of Wells
SPE 26042
Of higher importance was whether the perfs were protected or not.
3/14/2009 36George E. King Engineering
GEKEngineering.com
PI Change After Workover - Perfs Protected
-40
-30
-20
-10
0
10
20
30
40
50
1 2 3 4 5 6 7 8 9 10 11% C
hang
e in
PI
Short Term PI ChangeLong Term PI Change
0.3 1.2 3.1 4.6 8.4
PI of wells
SPE 26042
When perfs were protected, that was little risk of long term damage.
3/14/2009 37George E. King Engineering
GEKEngineering.com
Damage in Fractured Wells with Unprotected Perforations
-80
-70
-60
-50
-40
-30
-20
-10
01 2 3 4 5
% D
amag
e
PIi = 1.92PIi = 6.21
PIi = 7.55
PIi = 7.55
PIi = 18.1
When the perfs were not protected, the well was damaged.
3/14/2009 38George E. King Engineering
GEKEngineering.com
Effect of Scraping or Milling Adjacent to Open Perforations
-60-50-40-30-20-10
01020
1 2
% C
hang
e in
PI
Short Term PI ChangeLong Term PI Change
Perfs not protected by LCM prior to scraping
Perfs protected by LCM
SPE 26042
One very detrimental action was running a scraper prior to packer setting. The scraping and surging drives debris into unprotected perfs.
3/14/2009 39George E. King Engineering
GEKEngineering.com
Kill Pills: Summary of Overall Effectiveness in Non Fractured Wells
-25
-20
-15
-10
-5
0
5
10
1 2 3 4 5 6 7
% C
hang
e in
PI
Sized Borate Salts (4)
Cellulose Fibers (3)
Sized Sodium Chloride (12)
No Near Perf Milling (6)
Near Perf Milling or Scraping (3)
No Near Perf Milling (8)
SPE 26042
Near Perf Milling or Scraping (10)
HEC Pills No Pills
Sized particulates, particularly those that can be removed, are much less damaging than most polymers, even the so-called clean polymers.
3/14/2009 40George E. King Engineering
GEKEngineering.com
Third Problem
• We don’t know enough about timing of damage removal.– Variety of causes
• Polymer dehydration
• Decomposition of materials
• Adsorption, absorption and capillary effects
• Field data from Troika (100,000 md-ft) show initial flow improves PI, but later flow does not.
3/14/2009 41George E. King Engineering
GEKEngineering.com
Deepwater Well Cleanup Lessons
• On initial cleanup, PI erratically increased as choke opened. Typical response was a decrease, as if well / flow path were loading up, then sharp PI increase, seemingly when the obstruction was unloaded.
• Little partly broken polymer recovered, but early load water recovery matched PI incr.
• Lower skins were linked to both sand flow before completion (sand surge removed damage), increased cleanup flow volumes (and drawdown) on initial cleanup, and more effective frac stimulations.
3/14/2009 42George E. King Engineering
GEKEngineering.com
Deepwater Cleanup Lessons
• Wells cleaned up with increasing drawdown immediately following backflow start. Cleanup was increasing, measured by increasing PI, at the end of the first short cleanup periods prior to shut-in of the well.
• After initiation of production operations - after first cleanup flow, no further cleanup of damage was seen, regardless of drawdown. The reason is not known, but may be due to polymer adhering or cooking out?
3/14/2009 43George E. King Engineering
GEKEngineering.com
Fourth Problem
• We don’t understand how damage impacts economic return.
3/14/2009 44George E. King Engineering
GEKEngineering.com
Example Economics - Skin Sensitivity
100
110
120
130
140
150
160
170
0 5 10 15 20 25
Skin
PV-1
0, $
mm
10
15
20
25
30
35
40
PV10ROR
3/14/2009 45George E. King Engineering
GEKEngineering.com
An example of a completion method that minimizes damage.
• Perforating, but with enough underbalance to create the flow necessary to clean the perforations.
3/14/2009 46George E. King Engineering
GEKEngineering.com
Type ofDamage
MostProbableLocation
Impact onProductivityif notRemoved
SurgePressureNeeded forRemoval?
Flow Vol.Or TimeNeeded forRemoval?
RemovalHampered byLimits onCleanup Vol?
AlternateMethods ofRemoval orPrevention
Mud Cakein Pay Zone
FormationFace
Moderate toSevere
Yes SpurtVolume
Yes Acids, Soaps,Enzymes
Mud Filt. <12” Minor - mod. No NoWhole MudLoss
Fracturesand largevugs
Severe Possible,Can help infew cases.
Depend onCond. fewcasessimilar
Yes, flowcombined withsolventtreatment
Few successfulwhole mudremovals whenvol. > 200 bbls.
CementFiltrate
<12” intopay
Only if claydamage
No No
PerforationCrush Zone
½” aroundperf
Moderate toSevere
Yes 4 to 12gal/perf
Yes Surge smallzones intochamber, acids,pulses, fracs
Formationsand inperfs
perftunnels
Most severe Cleanupand reperf
Depends oninitial &lateractions
Develop goodperf andprepack actions
Look at some of the most common damage mechanisms. In some formations, a specific damage is very detrimental, while in another formation, the damage is insignificant.
3/14/2009 47George E. King Engineering
GEKEngineering.com
Type of Damage Skin range CommentsMud Cake in PayZone
+5 to +300,+15 is typical
Mud skin is usually shallow and has more impact whenturbulence and non-darcy skin problems are most severe. Mudcake is usually by-passed by perforating.
Mud Filtrate +3 to +30 Filtrate usually recovered by steady flow and time. Related torelative perm effects. This is usually a short lived problem (1 to3 weeks)
Whole Mud Loss (inpay zone)
>+50 Options depend on mud volume lost. Enzymes, solvents andacids for small volumes (<10 bbls). Sidetrack if over 1000 bbls.Low solids mud can be removed by concentrating on viscosifierdestruction or dispersment.
Cement Filtrate +10 to +20 Very shallow clay problems. Perforate with deep penetratingcharges to get beyond. Use leakoff control on cement.
Perforation CrushZone
+10 to +20 Perf small intervals underbalanced. Isolation packer breaksown,explosive sleeve breakdown (very simple) - must beaccomplished prior to gravel packing.
Formation sand inperfs
>+50 Most severe typical damage - cleanout and recompletionrequired
When looking at the range of skins, it is useful to know that some wells have high skins but are really restricted by other factors such as tubing flow limits, facility limits, etc., and are not really limited by the skins.
3/14/2009 48George E. King Engineering
GEKEngineering.com
Table 3: Completion Efficiency Factors (Stracke, SPE 16212) Shown as a percent of wellsin each bracketed completion efficiency range.Factor 100-75% 75-50% 50-25% 25-0%Underbalance perf w/ surge chamber 26 26 26 23Perforate and wash perfs 25 40 19 15Underbalance perf w/ surge chamber + wash perfs 71 14 14 0Surge Vol < 4 gal/ft 23 19 35 23Surge Vol > 4 gal/ft 43 29 14 14Surge differential < 1000 psi 27 24 24 24Surge differential >1000 psi 19 27 31 23Drilling overbalance <300 psi 15 48 19 19Drilling overbalance >300 psi 31 31 23 16Drilling overbalance >1000 psi 27 31 23 19Completion overbalance <300 psi 25 39 25 12Completion overbalance >300 psi < 600 psi 21 36 21 21Completion overbalance >600 psi 47 21 5 26
This data is difficult to understand unless the attention is focused at those factors which deliver the most wells in the 100% to 75% efficiency range, e.g., underbalance perf w/surge chamber and wash perfs.
3/14/2009 49George E. King Engineering
GEKEngineering.com
Table 4: Perforation Tunnel Volume Following Perforating at Different Conditions(Regalbuto and Riggs, SPE PE, Feb 1988)
Pressure Differential Hole Volume, perforated Hole Volume, perforated/surgedOverbalanced,500 psi, no surge
18 cc
Balanced perforated, no surge 31 ccUnderbalanced perforated, 500psi
20 cc 42 cc
Balanced perforated, delayed1000 psi surge
31 cc 48 cc
Underbalanced perforated, 1000psi
50 cc 75 cc
Notice that underbalance perforating at high underbalance (which causes flow) delivers a perforation that is from 40% to nearly 300% larger than the other methods of perforating.
3/14/2009 50George E. King Engineering
GEKEngineering.com
Back to over-all damage –What is it?
• Divide the well into three parts:– Inflow: area from reservoir to the wellbore– Completion potential: flow to surface– Surface restrictions: chokes, lines, separators.
• Basically, anything that causes a restriction in the flow path decreases the rate and acts as “damage.”
3/14/2009 51George E. King Engineering
GEKEngineering.com
4600 psi
1000 psi15 psi
10 psi
25 psi
100 psi
Column Densities:Gas = 1.9 lb/gal = 0.1 psi/ft = 1900 psi in a 10,000 ft well Dead oil = 7 lb/gal = 0.364 psi/ft = 3640 psi in a 10,000 ft well Fresh water = 8.33 lb/gal = 0.433 psi/ft = 4330 psi in a 10,000 ft wellSalt water = 10 lb/gal = 0.52 psi/ft = 5200 psi in a 10,000 ft wellGas cut flowing oil = 5 lb/gal = 0.26 psi/ft = 2600 psi in a 10,000 ft well
10,000 ft
Press.Drop
Differential pressure, ∆P, is actually a pressure balance
4600 psi reservoir pressure -2600 psi flowing gradient for oil- 150 psi press drop- 100 psi through the choke - 25 psi through the flow line- 10 psi through the separator- 15 psi through downstream flow line-1000 psi sales line entry pressure ----------------------
∆P = 700 psi drawdown pressure
Where does the ∆P come from?
1000
3/14/2009 52George E. King Engineering
GEKEngineering.com
The first step…..
• For the purposes of this work, consider the flow connection between the reservoir and the wellbore as the primary but not the only area of damage.
• Now, is it “formation damage” or something else that causes the restriction?
3/14/2009 53George E. King Engineering
GEKEngineering.com
Some sources of the “damage” in the reservoir-wellbore “connection”
• Wetting phases (from injected or “lost” fluids)• Debris plugging the pores of the rock• Polymer waste from frac and drilling fluids• Compacted particles from perforating• Limited entry (too few perforations)• Converging radial flow – wellbore too small• Reservoir clay interactions with injected fluids• Precipitation deposits (scale, paraffins, asphaltenes, salt,
etc)Note that not all are really formation damage – How do you
identify the difference?
3/14/2009 54George E. King Engineering
GEKEngineering.com
0
2
4
6
8
10
12
14
16
18
20
Tg 308 Tg 312bis Tg 315bis Teg 15y tg 307ter Tg 305bisz Teg 14z Teg 11z Teg 12z Teg 10z
Tota
l Ski
n
Turbulent Skin
Mechanical SkinCased Hole - Vertical - 5" Tbg
Open Hole - Vertical - 7" Tbg
Open Hole - Slanted - 7" Tbg
2001 2002
Turbulent Skins Normalized to Rates of 100 mmscfd
65-75 degree
15-20 degree
65-80 degree
50-65 degree
ALGERIAN GAS WELL COMPLETION EFFICIENCIES
60-70 degree
65-75 degree
And some restrictions – in very high perm wells – is the casing and the very limited amount of open area that perforations create.
Data comparing cased and perforated skin with skins from open hole completed wells from Algeria.
3/14/2009 55George E. King Engineering
GEKEngineering.com
Identification of Damage.
• How good are you at deductive reasoning?– Identifying the cause and source of damage is
detective work.• Look at the well performance before the problem• Look at the flow path for potential restrictions• Look to the players:
– Flow path ways– Fluids– Pressures– Flow rate
3/14/2009 56George E. King Engineering
GEKEngineering.com
What is Completion Efficiency?
• A measure of the effectiveness of a completion as measured against an ideal completion with no pressure drops.
• Pressure drops? – these are the restrictions, “damage”, heads, back-pressures, etc. that restrict the well’s production.
3/14/2009 57George E. King Engineering
GEKEngineering.com
Look again - The Effect of Damage on Production
Rate = (∆P x k x h) / (141.2 µo βo s)
Where:∆P = differential pressure (drawdown due to skin)
k = reservoir permeability, mdh = height of zone, ftµo = viscosity, cpβo = reservoir vol factors = skin factor
3/14/2009 58George E. King Engineering
GEKEngineering.com
What changeable factors control production rate?
• Pressure drop – need maximum drawdown and minimum backpressures.
• Permeability - enhance or restore k? - yes• Viscosity – can it be changed? – yes• Skin – can it be made negative?
• These factors are where we start our stimulation design.
3/14/2009 59George E. King Engineering
GEKEngineering.com
Formation Damage
• Impact• Causes• Diagnosis• Removal/Prevention?
• Basically, the severity of damage on production depends on the location, extent and type of the damage. A well can have significant deposits, fill and other problems that do not affect production.
3/14/2009 60George E. King Engineering
GEKEngineering.com
Conclusions
• Damage is usually shallow.
• Remove it or by-pass damage if it really causes a problem.
• Not every “damage” is in the formation.
• Not every drop in production is caused by damage.
• First, remove the pressure drops, everything else will take care of itself.
3/14/2009 61George E. King Engineering
GEKEngineering.com