8 3 2018-naps-24 laboratory observations of dynamic
TRANSCRIPT
2018-NAPS-24AUTHORS:DennisHaggertyandGeraldCraddock,JetResearchCenter- Halliburton
LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowand
ModerateStrengthFormations
Agenda
Ø DefineDynamicEffectiveStress(DES)andnoteitsimportance
Ø Briefdescriptionoftwotestcases
Ø ReviewCTscanimagesforeachtestcaseanddiscusstheresults
Ø Reviewfastgaugeresponsechartsfromsecondtestcase
Ø Conclusions/Comments
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
WhatisDES anditsimportance?
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Ø Itisthetransientstressaroundtheperforationtunnelatperforating
Ø Itreachesamaximumimmediatelyafterchargedetonation
Ø Durationistypicallybetween0.25and1.50seconds
Ø Itisaconsequenceofdynamicunderbalance
Ø Itissignificantforoptimizinggravelpackandinjectionoperations
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
1. Debris filled tunnel but with competent walls – more common with big hole (BH) vs. deep penetrating (DP) charges
2. Partial tunnel collapse – usually when DP charges are used
3. Failure with no tunnel walls – occurs when a wellbore underbalance is combined with significant effective stress on a low UCS formation
SPE distinguished lecturer Dr. Ian Walton: “Shear failure occurs when effective stress exceeds 3 to 5 times the UCS of the formation depending on tunnel diameter”. SPE-90123-MS (2004) “A rock with strong cementation is more likely to support a competent cavity than a rock that is weakly consolidated. However, strength alone does not tell the whole story of how the rock will behave after being perforated. The capability of the virgin rock to support a perforation cavity is dependent on the compressive load, the UCS and on the diameter of the initial cavity. Based on Thick-wall cylinder tests, a model of tunnel stability was developed at SLB Cambridge Research Center. The model shows that shear failure occurs when the effective stress around the tunnel exceeds a certain multiple of the UCS. The multiple depends on the diameter of the tunnel and is most commonly in the range of 3 to 5 with narrow cavities being stronger than wider cavities.”
DES: mechanism that determines the condition of the perforation tunnel
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
DeterminingDES
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Pressure,psi
ElapsedTime,seconds
MinimumWellborePressure(DynamicUB),pointofmax.DynamicEffectiveStress(DES)
Formation Pressure
Wellbore Pressure
OverburdenStress
DynamicUnderbalance(Dynamic UB):FormationPressure- min.WellborePressure
Dynamic EffectiveStress(DES)=(OverburdenStress- FormationPressure)+DynamicUB
PeakDES
FastGaugeChartofWellborePressureduringPerforating
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
API RP 19B Section 4 Testing Apparatus Setup
-OverburdenStressto25,000psi-FormationPressureto20,000psi-Temperatureto400°F
-CoreDia.to12in.-CoreLen.to48in.
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Detail Test1 Test2 Test3 Test4
Overburdenpressure/EffectiveStress(psi) 7,000/(3,400 - 3,756)
Formation- estimatedUCS(psi) Castlegate sandstone- 2,200(OMS-saturated)
SaltwashRedsandstone- 890(dry)
Wellborepressure(psi) 3,500 3,300 3,600 3,600
Formation(Pore)pressure(psi) 3,244 3,291 3,600 3,310
Per-chargefreegunvolume(cc) 240 180180180
Wellborefluid (OMS) 9-lbm/galBrine Odorlessmineralspirits(OMS)
Porosity(%) 26.0 20.0 to23.5
Permeability(md) 1000 2000 1850
StaticwellborePre-perf.condition(psi) +256 Balanced Balanced +290
Charge 45/8-in.Steel-cased bigholeHMX
Fluidgap(in.) 1.09
Casingthickness(in.) 0.408(4140Steel)
Cementthickness(in.) 0.75(ClassAPortland)
Corediameter/length (in.) 7.0(nominal)/24.0(nominal)
Porefluid OMS
Temperature(°F/°C) 77/25
Test Setup and Conditions for Set 1 at Low Pressure
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Test 1
Post–FlowCTimageshowsdebrisisremovedandperforationtunneliscompetent
Wellbore:3,500psi,PorePressure:3,244psi,StaticUB:256psi,DynamicUB:21psi,DES =7,000(Overburden)- 3,244psi+21psi=3,777psi
SafeDES/UCSratiois3-5
WithUCSof2,200psitheDES/UCSratio=1.7
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Test 2
Wellbore:3,300psi,PorePressure:3,291psi,StaticUB:9psi,DynamicUB:325psi,DES =7,000(Overburden)- 3,291psi+325psi=4,034psi
WithUCSof2,200psitheDES/UCSratio=1.83
SafeDES/UCSratiois3-5
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Test 3 and Test 4
Wellbore:3,293psi,PorePressure:3,326psiDynamicUB:284psiDES=7,000(Overburden)- 3,326psi+284psi=3,958psi
Wellbore:3,557psi,PorePressure:3,267psiDynamicUB:10psiDES=7,000(Overburden)- 3,267psi+10psi=3,743psi
SafeDES/UCSratiois3-5
WithUCSof890psitheDES/UCSratio=4.2
WithUCSof890psitheDES/UCSratio=4.4
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Detail Test1 Test2 Test3TargetDUB/DES(psi) 6,000/16,000 10,500/20,400 8,000/18,000Overburdenpressure/Effectivestress(psi) 26,000/10,000Formation- estimatedUCS(psi) Kansassandstone- 3,600(TerraTek2014)
(OMS-saturated)Formation(Pore)pressure(psi) 16,000 16,000 16,000Wellborepressure(psi) 16,200 16,200 16,200Wellborefluid OMS OMS OMSPorosity(%) 20.1 24.6 19.9Permeability(md) 30 30 30Staticcondition(psi) +200 +200 +200Charge(in.) 63/4Steel-casedbigholeHMXFluidgap(in.) 1.480Casingthickness(in.) 0.650 (17-4StainlessSteel)Cementthickness(in.) 1.19(ClassAPortland)Corediameter/length(in.) 9.00/18.00(nominal)Porefluid OMSTemperature(°F/°C) 77 /25
Test Setup and Conditions for Set 2 at High Pressure
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
WithUCSof3,600psitheDES/UCSratio=4.6
Wellbore:16,200psi,PorePressure:16,000psiDynamicUB:6,506psiDES=26,000(Overburden)- 16,000psi+6,506psi=16,506psi
SafeDES/UCSratiois3-5
Test 1
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
DESeffectseenbyhemisphericalfracturebandingcontainedwithintheBHimpactzone.
Wellbore:16,200psi,PorePressure:16,000psiDynamicUB:14,100psiDES=26,000(Overburden)- 16,000psi+14,100psi=24,100psi
SafeDES/UCSratiois3-5
WithUCSof3,600psitheDES/UCSratio=6.7
Test 2
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Wellbore:16,200psi,PorePressure:16,000psiDynamicUB:7,553psiDES=26,000(Overburden)- 16,000psi+7,553psi=17,553psi
SafeDES/UCSratiois3-5
WithUCSof3,600psitheDES/UCSratio=4.9
Test 3
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Fast Gauge Data For Test 1
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Fast Gauge Data For Test 2
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Fast Gauge Data For Test 3
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations
Conclusions/Comments
Ø Dynamic effective stress is the by-product of the dynamic underbalance and should be considered in dynamic underbalance design.
Ø It is the determinant for perforation tunnel collapse because that is the stress that can lead to failure, tensile and shear.
Ø Lower viscosity is favorable for avoiding collapse in terms of reducing the peak of DES and time exposure to high DES.
Ø Based on CT images from a similar HP testing project, DES effects on limestones should be considered separately, mainly due to narrower tunnels.
Ø DES can be modeled in shock hydro simulations with a modified rate-dependent strength model, a future plan.
The authors thank the APFL team for their efforts and Halliburton management for allowing the publication of this paper
Acknowledgements
2018-NAPS-24/LaboratoryObservationsonDynamicEffectiveStressAssociatedwithDynamicUnderbalanceonLowandModerateStrengthFormations