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-
ar ona e c z ng
osen : r. n ry a m,Universitas Trisakti - Jakarta
2012
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Objective/Sasaran
• Dan enera ann a
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Daftar Pustaka
• Allen S.O. and Robert A.P. ”Production Operation”, Vol. I Oil and Gasonsu an n erna ona nc.
• Peter E. Clark,”Well Completions : Stimulation and Work Over”.
• Pertamina Hulu,” Teknik Produksi”, Jakarta, 2003
• Unocal Completion Course Presentation
• BJ presentation, 2003
• Semua buku perihal Komplesi dan uji Sumur
• Semua Jurnal tentang Komplesi dan uji Sumur
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BJ Services
Formations
&
Matrix Acidizing
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Carbonates
Topics
1. Types of Formation
2. Mineralogy
3. Acid Types4. Treatment Design
5. Summary
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Carbonates
1. Types of Formation
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Carbonates
Types of Formation
Limestone
Comprised mainly of Calcium Carbonate
but may also contain Calcium MagnesiumCarbonate and Iron Carbonate
3 Types:-
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Carbonates
Types of Formation
Organic Limestones
orme rom e e e a es ues
of Marine Life
Relatively high porosity and high
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Carbonates
Types of Formation
Precipitated Limestones
Usually formed as Evapourites
Low Porosity
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Carbonates
Types of Formation
Clastic Limestones
Formed as Secondary Sedimentary
De osits
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Carbonates
Types of Formation
Chalk
ype o ne- ra ne mes one
u
ost y a c um ar onate
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Carbonates
Types of Formation
Dolomite
Calcium Magnesium Carbonate
Generally Harder and Less Permeable
than Limestones
Often with Natural Fractures
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Carbonates
Types of Formation
Marble
e amorp c mes one o om e
ery ar , very ow ermea y
Natural Fractures
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Carbonates
2. Mineralogy
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Carbonates
Mineralogy
Calcite
a c um ar ona e a 3
Usuall or anic in Ori in
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Carbonates
Mineralogy
Calcite
a 3 + a 2 + 2 + 2
Carbon Dioxide (CO2) stays in Solution Downhole,
But will Cause Foamin as the Acid is
Flowed Back to Surface
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Carbonates
Mineralogy
Dolomite
Calcium Magnesium Carbonate
CaMg(CO3)2
Very soluble in Acid
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Carbonates
Mineralogy
Dolomite
a g 3 2 +
a 2 + g 2 + 2 + 2
o om e equ res more c per oRock than Limestone or Chalk
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Carbonates
Mineralogy
Siderite
3
of Limestones and Chalks
Easily dissolved by Acid, but canresult in Iron Hydroxide precipitates
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Carbonates
Mineralogy
Siderite
e 3 + e 2 + 2 + 2
Ferrous Chloride can cause Ferrous
H droxide Preci itates if the Acid
is Neutralised
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Carbonates
Mineralogy
Ankerite
ron-r c o om e - a e g 3 2
of Dolomites
Very soluble in Acid, but canresult in Iron Hydroxide precipitates
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Carbonates
Mineralogy
Quartz
- 2
u
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Carbonates
3. Acid Types
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Carbonates
Acid Types
Hydrochloric Acid
HCl - also known as Muriatic Acid
Very reactive
in Carbonates
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Carbonates
Acid Types
Acetic Acid
CH3COOH - Also called Ethanoic Acid
Expensive - used as alternative to HCl
in High Temperatures
so use o con ro ron
Precipitates
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Carbonates
Acid Types
Formic Acid
HCOOH - Also called Methanoic Acid
Mildly reactive (stronger than Acetic)
Expensive - used as alternative to HClin High Temperatures
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Carbonates
Acid Types
Citric Acid
6 8 7
if reacted with Calcite
Mainly used in combination with Acetic
on its own.
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Carbonates
4. Treatment Design
• Acid type and Strength
• Corrosion Inhibitor
• ron on ro
•
• Special Additive
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Carbonates
Treatment Design
Acid Type
Good Reason to Use another Acid Type
At very High Temperatures, Acetic and/or
Formic Acid is Used because of Slower
Reaction Rate
,
Availability, Storage and Function
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Carbonates
Treatment Design
Acid Type
n very a er- ens ve orma ons
99% Acetic Acid can be Used, ass s ssen a y a er ree.
emem er t at rgan c c s areGenerally Weaker than HCl and will
equ re more an o ume
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Carbonates
Treatment Design
Acid Strength
rong c s sso ve more oc per
Gallon, Require less Storage Volume and
x
Inhibitor and Get Further from the Wellbore
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Carbonates
Treatment Design
Acid Strength
o ce o c reng epen s upon
BH Temperature, Available Storage
u v
Typical HCl Strengths:-7.5%, 15%, 28%
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Carbonates
Treatment Design
Corrosion Inhibitors
at which the Acid Attacks the Completion
and the BJ E ui ment
BJ Standard for Corrosion Protection
.
BJ Standard for Coiled Tubing Protection
is 0.02 lbs/sq ft Metal Loss or Less
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Carbonates
Treatment Design
Corrosion Inhibitors
Inhibitor Intensifiers are used at
Higher Temperatures to Boost theEffectiveness of the Inhibitors
orros on n ors are xpens veand highly Toxic
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Carbonates
Treatment Design
Corrosion Inhibitors
,
Job-Specific Testing:-
• empera ure
• Exposure Time
• - - ,
• CO2 and/or H2S Level
• Mutual Solvent Loadin
• Acid Type and Strength
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Carbonates
Treatment Design
Pumping Rate
or ear e ore amage emova ,
Removal or Gravel Pack Cleanouts, pumpa . o . pm.
Near Wellbore Area. Deep Penetration
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Carbonates
Treatment Design
Pumping Rate
or a r x mu a on, ump a ax mum
Possible Rates, Staying below 80% ofe rac ra en
“ ” through the formation if the rate
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Carbonates
Treatment Design
Pumping Rate
Paccaloni-St leMatrix Treatments Involve
Increasing the Rate, as the Acid
Stimulates the FormationThese Treatments can start at 2 - 3 bpm
& Finish at 40 + b m
Paccaloni treatments with diversion
Provide the Best possible stimulation
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ACIDIZING
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Dasar Acid Frac
• Acid diinjeksikan melebihi kondisi fracture
• Diaplikasikan pada reservoir Limestone dan Dolomite
• Permukaan fracture (fracture face) terlarut oleh asamyang menyebabkan terbentuknya conductive channel
• Panjang dari fracture ditentukan oleh jenis acid,volume kekuatan acid arameter leakoff dan
kecepatan reaksi
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Kandidat Acid Frac
• Clean formasi limestone dan Dolomite
– Harus memiliki fracture containment/barrier yang cukup untukmendapatkan panjang (Xf)
• Batuan dirty carbonate (< 70% kelarutan pada HCl) adalah kandidat yang jelek
– Material tidak terlarut oleh HCl yang terlepas bisa menutup fractureataupun masuk ke wellbore yang bisa menyebabkan perforasi tertutup(sandfill)
– Lunak, sehingga tidak bisa menjaga conductivity setelah fracturemenutup
•
– HCl, bahkan HF tidak cukup untuk melarutkan permukaan fracture
– Material yang terlepas karena terlarutnya batuan akan menutup fracturean ada
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GENERAL PRINCIPLESThe primary purposes of any acidizing treatment is to dissolveeither the formation rock or materials, natural or induced, within
the pore spaces of the rock.
There are two primary requirements that an acid must meet tobe acceptable as treating fluid :
.
soluble products
2. It must capable of being inhibited to prevent excessive
reaction with metal oods in the wellOther important consideration are cost, avai labil ity, and safety
in handling.
Major types of acid in well treatment :1. Hydrochloric Acid
2. Hydrofluoric Acid
3. Acetic Acid
4. Formic Acid
Perbandingan Acid Frac dan
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Perbandingan Acid Frac dan
roppan rac
• Unit Frac Sederhana Komplit
• Proppant Flowback Tidak Ada Bisa Terjadi
• Fluid Loss Control Jelek Bagus
• Kandidat Karbonat Sandstone + Karbonat +
Shale + Batubara (CBM)
• a a a
• Fracture Length Pendek Panjang
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HYDROCHLORIC ACID (HCl)
Used in the field is normally 15% by weight HCl;
however, acid concentration may vary between
. ,
chalk, dolomite, and most other carbonates.Chemical reaction equation :
2HCl + CaCO3 CaCl2 + H2O+CO2
1000 gallons HCl of will dissolve approximately
10.8 cu ft (1,840 lbm) of limestone. It will liberate
,2
,
2,042.4 lbm of calcium chloride (dissolved in the
original water of the acid solution), plus 38.75 gal
of water formed during the reaction.
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Acetic and Formic Acid
Acetic acid (CH3COOH) and Formic acid (HCOOH) are weakly
ionized, slow reacting, organic acids. They are used much less
frequently than HCl and are suitable primarily fro wells with high
bottom hole temperatures (> 250o
F) or were prolonged reactiontimes are desired. The reaction of these acids with
2HOrg + CaCO3 CaOrg2 + H2O + CO2
For field use, HAc and HCOOH solutions normally are diluted to
15% and 10%, respectively.
Above this concentration will reci itate CaOr from its ‘s ent
acid’ solution because of its l imited solubil ity.HCl sometimes mixed with HCOOH or HAc to increase
dissolving power per gallon of acid also will provide extended
reaction times.
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HYDROFLUORIC ACID (HF)
Used in combination with HCl and has been
referred to as ‘intensified acid’ or mud removal
. .
HF is used primarily to remove clay-particledamage in sandstone formations, to improve
permeability of clay-containing formations, to
increase solubility of dolomitic formations.
2HF + SiO2 SiF4 +2H2O
2HF + SiF4 H2SiF6
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ACID REACTION RATES
A knowledge of the factors affecting the reaction rate
.
1. Guide for a selection Acid type and volume.2. Determine how far a given formulation can
penetrate nto ormat on e ore spen ng actors
govern spending time).
Many factor govern the reaction time of an acid :
1. Pressure
.
3. Flow Velocity4. Acid Concentration
. rea o ume a o
6. Formation Composition
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1. Corrosion Inhibitors
2. Surfactants3. Silicate-Control Agent
4. Iron-Control Agents
5. Alcohols6. Gelling and Fluid Loss Agents
7. Liquefied Gases
8. Retarded Acid
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ACIDIZING TECHNIQUES
Three Fundamental techniques used in acidizing treatment :
.
This entails fill-up and soak of acid in the wellbore. Fluid
movement is at minimum unless some mechanical means of agitation is used.
2. Matrix Aciding
This is done by injecting acid into the matrix pore structure of
the formation below the fracturin ressure. Flow attern isessentially through the natural permeability structure.
3. Acid Fracturing
.
pattern is essentially through hydraulic fracture; however,much of the fluid does leak off into matrix along the fracture
face.
F d t l D i P d A id
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Fundamental Desain Pada Acid
Fractur ng• Menda atkan enetrasi acid fracture an
diinginkan
- BHST < 200°F, gunakan acid langsung dan leakoff rendah
- BHST > 200°F, tambahkan cooling down fluid + retarder untuk acid
• Fracture length harus dibatasi Jika tidak ada barrier yang membuat fracture tumbuh ke lapisan atas/bawah
• Memaksimalkan injection rate
50
Dibatasi oleh kekuatan maksimum wellhead/tubing
Factor Yang Mempengaruhi Fracture
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Factor Yang Mempengaruhi Fracture
eng on uc v y
• en s c , s reng an vo ume
– Berpengaruh pada lebar dan panjangnyafracture lengths
•
– Berpengaruh pada terbentuknya wormhole
• Viskositas Acid
– Mempengaruhi fracture width dan proses transportasi sepanjang fracture
• Injection rate
– Mempengaruhi panjang/tinggi fracture• Formation type
51
– Mineralogy, temperature
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Mekanisme Yang Terjadi Dalam Acid Frac
Acid Transport
c eac on
Acid Leakoff
52
Optimasi Conductivity & Etched
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Optimasi Conductivity & Etched
rac ure eng
• • o eore ca m a on o con uc v y
value• -
• • Maximum stimulation ratio achieved • - Corresponds to the case of infinite conductivity fracture
• •
k w f
k f
50
C t h P A id F
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Contoh Program Acid Frac
• DataFRAC* Service, consisting of:
–
– Step Rate Test using 2% KCl brine – Calibration Test using 2% KCl brine
• Main Acid Fracturing Treatment, consisting of:
– Solvent Preflush (10% mutual solvent)
– Spacer (15% HCL)
– Diverter Stage (viscoelastic fluid, etc)
– a n c ys em emu s ac
– Solvent Postflush (10% mutual solvent)
– –
C t h P A id F
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Contoh Program Acid FracJob Execution
Stage Name Stage Fluid
Volume
Cum. Fluid
Volume
Stage
Time
Cum.
Time
(gal) (gal) (min) (min)
DIVERTER 1200.0 1200 2.0 2.0
SPACER 210.0 1410 0.4 2.4
ACID 800.0 2210 1.4 3.8
SPACER 210.0 2420 0.4 4.1
DIVERTER 1200.0 3620 2.0 6.2
SPACER 210.0 3830 0.4 6.5
ACID 800.0 4630 1.4 7.9
SPACER 210.0 4840 0.4 8.2
DIVERTER 1000.0 5840 1.7 9.9
. . .
ACID 600.0 6650 1.0 11.3
SPACER 210.0 6860 0.4 11.7
FLUSH 2815.7 9676 4.8 16.5
Contoh Program Acid Frac
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Contoh Program Acid Frac
Initial Fracture To TVD 7411.4 ft
Initial Fracture Bottom TVD 7422.8 ft
Etched Fracture Half-Length 60.1 ft
Average Etched Width 0.212 in
Average Conduct ivi ty 34127 md.ft
.
Net Pressure 74 psi
EOJ Efficiency 0.092
C b t
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Carbonates
Summary
Matrix Acidizing in Carbonates is UsuallyRelatively Easy. If you Pump Acid into
a Carbonate, you should get an
Increase in Production
upon the Temperature, the Formation Type
,
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Question ?