Matrix Acidising

8/10/2019 Matrix Acidising

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MATRIX ACIDISING


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INTRODUCTION

Overview of Acidising

Sources of Formation damage


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LEARNING OUTCOMES

At the end of this lecturer, students should be able to:

Design acidising treatment

Assess the degree of formation damage present in a

formation


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ACIDISING

Uses of Acid in the oilfield:

Wellbore cleaning

Formation damage removal

Source, tpe, location, form of damage

Formation stimulation

!atri"

Fracturing


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WHERE IN THE WELL?

#reat in the wellbore above open formation

$ %rotect lower completion

$ %revent well flow

Wash well across formation

$ &lean screen$ %erforation wash

!atri" treat

$ 'solation (tpe of completion)

$ *elow Frac pressure

Frac

$ Above Frac %ressure

$ %rotect completion pac+er

$ !a need isolation

Keep fluid out of Matri

!luid "ill #o$ta#t Matri


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ACIDISING

#wo tpes of oc+

#wo tpes of -oal

#wo tpes of #reatment

#wo tpes of !atri" Acidi.ing

#wo tpes of Acid


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ACIDISING

#wo tpes of oc+:

&arbonates (/imestone)

$ &alcite, dolomite

$ %orosit in matri", vugs, fractures

$ !atri" perm often low

&lastics (Sandstone)

$ 0uart. and other alumino 1 silicates$ %orosit between particles

$ %ermeable matri" between particles


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ACIDISING

#wo tpes of #reatment:

!atri" Acidi.ing

$ &lastics

for damage removal$ &arbonatesfor stimulation

Fracturing

$ 2draulic Fracturing$ Acid Fracturing


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!LOW REGIMES

adial flow

3atural fractures

2draulic fractures

Matrix Production Fracture Production


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MATRIX ACIDISING

#wo tpes of !atri" Acidi.ing:

$ Dissolve mineral structure to

build pathwas to natural

fractures or natural porosit$ %ush acid through matri"

framewor+, dissolving damage

and restoring natural perm


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ACIDISING

#wo tpes of Acid:

Acid that dissolves alumino1silicates

$ 2drofluoric Acid (2F)

Acid that dissolves carbonate material

$ 2drochloric Acid (2&'), Organic Acids


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H%DROCHLORIC ACID &HCL'

/ow cost and availabilit

Strengths used 41567

8"cellent reaction rate with calcite 1 controllable

8conomical &orrosion inhibition possible up to 9;


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ORGANIC ACIDS

Acetic

Formic

&itric

Others $ Sulphamic

Formic Acid (2&OO2)

$ !ostl used with 2&l or Acetic$ !ore e"pensive

$ %rimar application in hot wells

$ Useful in >slower reacting? acid fracturing sstems

Acetic Acid (&24&OO2)

$ Used in both carbonates and sandstone

$ &an be used in with 2&l or formic

$ &an be used alone instead of 2&l

$ /ower reactivit$ /ower corrosivit 1 less costl to inhibit

$ 2igh temperature applications


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ACID CONCENTRATIONS


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H%DRO!LUORIC ACID &H!'

Alwas pumped as a mi" of 2F and other acid

3ormal concentrations 2F @;7 to B@7

&an be inhibited to over 9;


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TREATING MATRIX DAMAGE WITH H!

2F is ver good at

removing damage

$ For safet reasons, usuall

mi"ed from Ammonium

*ifluoride with 2&/

$ &alled !ud Acid

#o reduce this damage

the ratio of 2&/ to 2F has

been increased from 95:4

to 9@:9; even to C:9

$ with additional 2&/

(preflush postflush)

to +eep the p2 low

*ut mud acid can also cause damage

$ %recipitation from reactions with:

&alcium &ompounds

!etallic &ations

'ron &ompounds

Silicates (&las and Feldspars) $ is+ of deconsolidation

most reaction in few cms

*ut increased 7 age of 2&l has its

own problems

$ &orrosion $ 'nhibitor

$ 2andling

And there is reduced 2F available


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ACIDISING ADDITI(ES

3earl alwas necessar:

&orrosion inhibitor

'ron control agent

Surfactant

Others:

3eed should be demonstrated or Eustified


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CORROSION INHI)ITORS

Alwas necessar

&an be damaging (oil1wetting) when used in e"cess

&oncentration depends on acid strength, tpe,

temperature, metal tpe, Eob duration

At higher temps, and for special steel, lab testing is

recommended 1 for inhibitor intensifier selection and

loadings


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IRON CONTROL AGENTS

'ron is ver soluble in most oilfield acid

&annot be avoided

'ron precipitate can be ver damaging

&hemical control within main treatment

'ron se=uestering agents iron reducing agents

'ron control is especiall important in inEection

wells


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WATER*WETTING SUR!ACTANT

Aids in clean1up of acid

/eaves formation surfaces water1wet

Different re=uirements for sandstones or carbonates

8nhances flow1bac+ of oil or gas

&oncentration must be limited (G H97)

8"cessive use can cause emulsion or foaming

in production processing e=uipment


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IDENTI!%ING THE NEED !OR ACID

Does damage e"ist II

2ow much II

Where II

What cause II


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ECONOMIC CONSIDERATIONS

'dentifing impaired production is not enough

#he production potential must be determined

$ 8ven if damage e"ists, the treatment ma not be

economical if the production improvement potential is ver small

&ost of Eob vs pabac+

$ &ost ma depend on location, Eob duration, lost

production$ &onsider pabac+ in short term, consider also

cumulative value


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COM+ONENTS O! SKIN

st J scKf K sp K sd

scK f 1 partial completion

fraction of the interval is perforated

well is deviated

sp1 s+in due to incomplete perforations

damaged perforations

insufficient shot densit

sd1 s+in due to damage


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E!!ECT O! SKIN


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NODAL ANAL%SIS


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SOURCES O! DAMAGE

Sources of Formation Damage:

$ Drilling

$ &ementing$ %erforating

$ &ompletion and Wor+over

$ -ravel pac+ing

$ %roduction$ Stimulation

$ 'nEection


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USING ACID

Follow Safet %rocedures

8nsure &orrect %%8 is used

&hec+ the %aperwor+

$ !SDS$ &hemical is+ assessment

&OS22

$ Lob is+ Assessment


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ACID +ROCEDURES

2O/D SAF8#M !88#'3-

$ #pes of fluids and ha.ards of each

$ Safet e=uipment to be worn

$ #reatment %rocedure

!a"imum %ressure %umping ate

Schedule bac+side rate or

monitoring procedures

$ eview Eob assignments for each individual

$ Obtain headcount of A// personnel on location

$ Designate 8mergenc Nehicle

who will drive it

DO 3O# move inEured person until inEuries are +nown


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+RESSURES

Surface #reating (pump) pressure

Friction pressure (tubing, perforation)

2drostatic pressure

*ottom 2ole pressure

Formation (pore) pressure

Fracture pressure


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TREATMENT DESIGN

Determine thecause and tpe of formation damage

'dentif e"tentand location of damage

Design the treatment to clean up that damage and to

prevent additional damage

#he treatment must be able to be placed properl

(Access, Diversion, &oil)

%hsical limitationsof well e=uipment


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IN,ECTION +RO!ILE

Depends on flow capacit $ +h

and pressure differential $ d%

$ emember that acid will change the +h

&an be controlled

$ !echanical 'solation (bridge plug, s=uee.e pac+er, straddle)

$ Diverters (solids, wa", polmers, surfactants, foams)

$ %lacement (coiled tubing)


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+LACEMENT

%lacement depends on:

$ &ompletion design

$ Lob re=uirements

9) &ompletion Design

$ &ased and %erforated 1 -ood access 1 good isolation

$ Open 2ole 1 -ood access 1 isolation variable

$ %redrilled or Slotted /iner 1 poor annular isolation

$ Standalone Screens 1 poor annular isolation

$ -ravel %ac+ed Screens 1 damage ma be in -%, formation, both

$ %roduction tubing pac+ers 1 limiting access

5) Lob re=uirements

$ #otal &overage 1 inEect into whole interval

$ Nolume, rate 1 &oil or *ullhead

$ Other .ones 1 oil or water .ones 1 protect or avoid waste

$ &ost 1 *ullhead vs &oil 1 Eob economics 1 volumes 1 control


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COILED TU)ING UNIT &CTU'


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-UESTION ??

THANK %OU

Matrix Acidising

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