Post on 02-Jun-2018
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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