Zisis Vryzas - Final Poster 2014

Determiningyieldstresswithdirectandindirect
measurements
Presenter:ZisisVryzas/co-author,Prof.VassiliosC.Kelessidis
Drillingfluidsmaycausedamagetoformationwhichoftenisremovedthroughacidizingandacidfracturing.Oneofthemain
rheologicalpropertiesofdrillingfluidsistheyieldstress.YieldStressisdefinedastheminimumorcriticalshearstressrequiredto
initiateflowandisrelatedtothestrengthofthenetworkstructuresofamaterial [1].
Knowledgeofyieldstressisnecessaryindrillingindustry:
Onedistinguishestwotypesofyieldstress[1,2]:
• Suspendingweightingsolids
• Dynamicyieldstress:Asamplewithastructurethathasbeen
• Transferringdrillcuttingstosurface
disruptedbyshearhasalowermagnitude
• Addressingtendencyofdrillingfluidtocauseformation
• Staticyieldstress:Asamplewithundisruptedstructurehasahigh
valueofyieldstress
damage
Themagnitudeofyieldstressdependson:
• theaccuracyoftheequipment
• thetimescaleofobservation
• Theextentofalterationofstructureofthesample
bypriorshearing
Yield Stress Estimation
DirectMeasurements
IndirectMeasurements
• Dataobtainedfromvanerheometer(Figure1)
• Staticyieldstressdirectlyobtainedfromvanetest(Figure2)
Vanemethod
- Thevanehasusually4bladesandisrotatedatveryslowspeed
- Itisrotatedataconstantrateuntilthetorqueexertedonthe
vaneshaftreachesamaximumvalueTm,andthesamplefails
Advantagesofvanemethod
• Minimaldestructionofsamplestructureduringloading
• Minimizationofwall-slipeffectsatthevaneedge
• Abilitytoanalyzesamplestooweaktowithstandshaping
EQUIPMENT
• Dataobtainedfromconventionalviscometer(Figure3)
• Extrapolationofshearstress– shearratecurvetozeroshearrates
(Figure4)
• Dynamicyieldstressaccordingtomodelemployed
Herschel-Bulkley model
Ithasproventobeagoodchoiceformanycases[2]
τ =τ HB +K(𝛾̇ )n
τ HB :theHerschel-Bulkley yieldstress,K:flowconsistencyindex
n:flowbehaviorindex
EQUIPMENT
Figure3:GraceM3600
Viscometer
Figure1:VaneRheometer Figure2:ShearStressvsTime
Objectivesofthiswork
• Illustratethephenomenaandmechanismsassociatedwith
theyieldstressdevelopmentwithdifferentadditives(smartfluids)
• Understandhowyieldstressmayaffectformationdamage
characteristicsofdrillingfluidswithdifferentandneweradditives
Smartdrillingfluidsdesiredcharacteristics
• Theyallowaveryprecisecontrolofpressuresalongthewellbore
• Improvedeeppenetrationrates
• Stableperformanceatdifferenttemperatures
Rheologicaltestingadditives
• Nanoparticles
• Poly-Anionic-Cellulose(PAC)
• Na-Carboxyl-Methyl-Cellulose(CMC)
• Partially-Hydrolyzed-Poly-Acrylamide(PHPA)
PETROLEUM ENGINEERING PROGRAM
“choosethis”
Figure5:YieldStressvsRPM
Figure4:ShearStressvsShearRate
Figure4:τHB =2.3Pa
Figure5:τvn =3.58Paat0.01rpm
• Optimalpointformeasurements :
0.01rpm
• Astherpm,τvn alsoandthe
differencebetweenτHB andτvn
increases
• Achievecloseryieldstressvalues
betweenGraceviscometerand
yieldrheometerat0.01rpm
References:
[1]V.C.Kelessidis,R.Maglione,Yieldstressofwater-bentonite
dispersions,ColloidsandSurfacesA:Physicochem.Eng.Aspects
318(2008)217-226
[2]V.C.Kelessidis,R.Maglione,C.Tsamantaki,Y.Aspirtakis,Optimal
determinationofrheologicalparametersforHerschel-Bulkley
drillingfluidsandimpactonpressuredrop,velocityprofilesand
penetrationratesduringdrilling,J.Petrol.Sci.Eng.53(2006)
203-224
“ThispublicationwasmadepossiblebytheNPRPaward[NPRP9-828-2-316]
fromtheQatarNationalResearchFund(amemberoftheQatarFoundation).
Thestatementsmadehereinaresolelytheresponsibilityoftheauthors”.