8 3 2018-naps-24 laboratory observations of dynamic

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?


Ø Itisthetransientstressaroundtheperforationtunnelatperforating

Ø Itreachesamaximumimmediatelyafterchargedetonation

Ø Durationistypicallybetween0.25and1.50seconds

Ø Itisaconsequenceofdynamicunderbalance

Ø Itissignificantforoptimizinggravelpackandinjectionoperations


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


DeterminingDES

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

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


API RP 19B Section 4 Testing Apparatus Setup

-OverburdenStressto25,000psi-FormationPressureto20,000psi-Temperatureto400°F

-CoreDia.to12in.-CoreLen.to48in.


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


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


Test 2

Wellbore:3,300psi,PorePressure:3,291psi,StaticUB:9psi,DynamicUB:325psi,DES =7,000(Overburden)- 3,291psi+325psi=4,034psi




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


WithUCSof890psitheDES/UCSratio=4.2

WithUCSof890psitheDES/UCSratio=4.4


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



Wellbore:16,200psi,PorePressure:16,000psiDynamicUB:6,506psiDES=26,000(Overburden)- 16,000psi+6,506psi=16,506psi


Test 1


DESeffectseenbyhemisphericalfracturebandingcontainedwithintheBHimpactzone.




Test 2





Test 3


Fast Gauge Data For Test 1


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


QUESTIONS?THANKYOU


8 3 2018-naps-24 laboratory observations of dynamic

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