carbonate acidizing ah

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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


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


,

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

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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

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– Mineralogy, temperature


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Mekanisme Yang Terjadi Dalam Acid Frac

Acid Transport

c eac on

Acid Leakoff

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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

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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



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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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carbonate acidizing ah

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