re-stimulation strategy - a bakken field study · 2018-05-30 · re-stimulation strategy - a bakken...

Re-Stimula tion Stra tegy - A Ba kken Fie ld StudyAshley Thoma & Lionel Ribeiro

WBPC – Williston Basin Optimiza tionMay 23 20 18

Open

Outline

Why/When do we Recommend Refracs?

Refrac Candida te Selection

Pilot Testing Results

Bakken Re-frac Campa ign Results

Conclusions

2 | WBPC - Restimula tion Stra tegy

Open

Why Refra c?

Parent Well Refrac

Unbounded existing producer(s)

New drill offsets

Protect & revita lize pa rent well

Prevent fracture asymmetry on child wells

Pare

nt W

ell

Pad Unit Refrac

No future development

All wells producing

Improve over legacy completion design

Fully developed 4MB x 4TF unit

Infill development with single-well producer


Open

Pressure Communica tion

Larger pressure communica tion toward depleted wells

Shorter fractures in virgin rock

Microseismic

Significant activity toward depleted wells

Fewer events on immedia te child wells

Chemica l Tra cers

Large ea rly-time communica tion toward depleted wells

Direct fluid communica tion

Surprise , Surprise…

Consistent evidence of subpar performance of child wells next to depleted wells (w/o re -stimulation)


Well being fra c’ed

Depleted well

Open

Pa rent Well Refra c Objectives


Improve Child Wells

Improve Parent

Well

Protect Parent

Well

Lower Ops. Costs

Limit a symmetric fra cture propa ga tion

Limit Three Forks- to-Middle Ba kken communica tion

Re-energize existing fra ctures

Conta ct new reservoir rock

Avoid excessive sa nd/wa ter loa ding in wellbore

Best cost opportunity to execute refra c

Open

Refra c Methods

Pump a nd Pra y

No downhole intervention, cost efficient

Poor la tera l coverage

Ineffective fracture crea tion

Mecha nica l Isola tion

Risky

Expensive

Questionable deployment for legacy open-hole swell packers design

Chemica l Diversion

No downhole intervention, less risk

Cost efficient

Acceptable la tera l coverage?


Open

Ca ndida te Se lection


Well IntegrityPressure test, PBR

length, tie -ba ck insta ll, CBL/TOC

FinancialUplift required to justify investment,

ops risks

ReservoirChild well se tup, deple tion timing,

inte r-well communica tion

Understa nd a nd ma na ge risks to se lect suita ble ca ndida tes

Producing Time

Cum

Oil

Too ea rly? Too la te?

Pa d configura tions

Open

First Refra c Pilots

First two refracs in Aug. 20 16 in Williams County

Wells selected a s pa rent wells in unit to be fully developed

Initia l completion and well design representa tive of the legacy design pre-20 14

o Uncemented liners with 34 PnP stages

o Legacy 4 MMlb proppant, 70 Mbblfluid design

o On production since 20 11/20 12 with tota l fluid (i.e. oil + wa ter) volume >50 0 Mbbl per well before refrac

Extensive diagnostic deployment


J a ck 21-16 # 1HRuth 28-33 # 1H

Open

Refra c Pilots – Opera tions

Refrac

Pad

Refrac Design – Parent Wells Complete both re-fracs first

Low-ra te pre-fill

Bull-head stimula tion trea tment

1.5 MMlb sand, 70 Mbbl fluid, vendor diversion materia l

Frac Design – Child Wells Complete immedia te offsets to pa rent well first

Three Forks: 6 MMlb sand & 130 Mbbl fluid

Bakken: 6 MMlb sand & 20 0 Mbbl fluid


Refrac

Open

Refra c Pilots – Dia gnostics

Refrac

Refrac

Pad

Surfa ce Microse ismic

Pressure Monitoring

Chemica l Tra cers

Downhole Microse ismic

Surface & Downhole Microseismic Latera l coverage during re-frac

Fracture overlap between wells

Fracture asymmetry and height growth

Pressure Monitoring Fracture overlap nea r the heel Indica tion of fracture asymmetry

Chemical Tracers Fluid communica tion during ea rly production Constra ints to microseismic results


Open

Refra c Pilots – Opera tions

Pre-Fill Injection Managed to re-pressurize the well a t 95% of the

initia l ISIP within the ta rget volume and ra te

Low-ra te pre-fill improves subsequent re-frac la tera l coverage

Refrac Design Frequent small-volume diversion pills

Adequa te fluid viscosity to improve proppant transport

Low proppant concentra tion

Mainta in ra te a s high as possible without interruption


WellAWellB

Fra c gra dient

Open

Surfa ce Microse ismic Da ta

Key Observations Possible to stimula te >75% la tera l with diversion job in

un-cemented well (10 ,0 0 0 -ft la tera l)

Latera l coverage shrinks over time

Results confirmed in subsequent Microseismic survey

Well A Well B

270 0 sta tions in 70 -ft interva ls


10 ,0 0 0 -ft wells60 0 -ft spa cing

Open

Pa rent Well Production

Refracs demonstra ted substantia l EUR uplift (+35% range)

Initia l ra te improvement over 5 x pre-refrac with susta ined pressure support

Refracs were economica l by themselves (i.e. w/o including potentia l benefits on child wells)

Well B∆Oil ~ 220 MBO∆EUR ~ 50%

∆Oil ~ 150 MBO∆EUR ~ 28%

Well A


Open

Limiting Asymmetry on Child Wells

Key Observations Observed severe fracture asymmetry toward

pa rent wells w/o pa rent well re-stimula tion

Refrac lessened asymmetry toward depleted well

Refrac contributed to better fracture placement, and therefore better production of child wells

Well A (Refra c’ed) Well C (Not re -stimula ted)

New Well

Downhole microseismic Surfa ce microseismic


New Well

Open

Child Well Production

Thanks to pa rent well refrac, production of child wells immedia tely next to pa rent well is consistent with the average well performance in the a rea

Production loss >25% is common for immedia te child wells otherwise

Cum

Oil (

MBO

)

Month

Regiona l Type CurveImmedia te Child wellsNew wells a wa y from pa rent


Cum

Oil (

MBO

)

Month



w/ parent well refrac w/o parent well re -stimulation

Open

Ba kken Refra c Ca mpa ign to Da te

12 refracs successfully pumped to da te

o Uncemented liner wells with >30 stageso Initia l completion with >3MMlb proppant

>10 more refracs planned in next 6 months

Refracs executed in Williams, McKenzie, and Mountra ilcounties

1 instance where decided to cancel refrac opera tions due to mechanica l issue during well prep

Severa l instances where project approva l was cha llenged by non-consenting pa rtners


Open

Well Prep

Pre-frac pressure test

Tie-back insta ll

Pre- and/or post- clean-out run(s)

Depletion Timing

Well on vacuum ahead of prep

Identifying when/where depletion is too important and cannot be overcome

Understand connectivity to other wells

Logistics

Continuous frac opera tions a re important to ma inta in la tera l coverage

Supply cha in optimiza tion

AL method to handle higher wa ter cut

Opera tiona l Lea rnings

Understanding and mitigating risks to manage large -scale implementation


Open

Conclusions

1. Refracs lessen the nega tive impact of a symmetrica l fracture growth a round depleted wells

2. Refracs can be economica l by themselves

3. Diversion stra tegy works even without mechanica l isola tion

4. Currently deploying pa rent well refrac stra tegy a t la rge sca le

5. Engage well pa rtners ea rly to ga in approva l


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Ashley Thoma & Lionel RibeiroRe-Stimulation Strategy - Bakken Field Study

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re-stimulation strategy - a bakken field study · 2018-05-30 · re-stimulation strategy - a bakken...

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