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Optimizing Refracture Optimizing Refracture Treatments in Horizontal Shale Treatments in Horizontal Shale

Oil and Gas ReservoirsOil and Gas Reservoirs

SPE Gulf Coast SectionSPE Gulf Coast SectionCompletions and Production Study GroupCompletions and Production Study Group

May 25May 25thth, 2011, 2011

Robert BarbaRobert BarbaIntegrated Energy Services IncIntegrated Energy Services Inc

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Horizontal Shale Well HistoryHorizontal Shale Well HistoryAll shale playsAll shale plays--continuous learning curve in continuous learning curve in

number of frac stages and length of lateralsnumber of frac stages and length of lateralsBakkenBakken--first first fracsfracs single stage 1500 ft lateralsingle stage 1500 ft lateralRecent wellsRecent wells--over 40 stages 11,000 ft lateralsover 40 stages 11,000 ft laterals

Similar trends in all shale playsSimilar trends in all shale plays

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Horizontal Shale Well IssuesHorizontal Shale Well IssuesHow can new wells be set up to take How can new wells be set up to take

advantage of the inevitable learning curve?advantage of the inevitable learning curve?What wells are good candidates for What wells are good candidates for refracsrefracs??How can treatments be optimized? How can treatments be optimized?

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Expected Learning CurveExpected Learning CurveBetter performing fluidsBetter performing fluids--Slickwater has major settling issuesSlickwater has major settling issues--is is

significant significant unproppedunpropped height only in high height only in high modulus Barnett?modulus Barnett?

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Expected Learning CurveExpected Learning CurveBetter performing proppantsBetter performing proppants--Widespread use of white sand at high Widespread use of white sand at high

closure stresses closure stresses --is it too early to see long is it too early to see long term effects of term effects of drawdowndrawdown??EFSEFS--S. S. TxTx Vicksburg wells use ISP and Vicksburg wells use ISP and

Bauxite at lower stressBauxite at lower stress

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Expected Learning CurveExpected Learning CurveFrac spacing based on permeabilityFrac spacing based on permeabilityStage spacing of 350Stage spacing of 350--450 ft assumes 450 ft assumes

40004000--10,000 10,000 ndndHighest published DFIT data 500 Highest published DFIT data 500 ndnd180 ft maximum frac spacing at 500 180 ft maximum frac spacing at 500 nd nd

maximum permmaximum permIs increased production from longer Is increased production from longer

laterals due to number of stages or the laterals due to number of stages or the length of the lateral?length of the lateral?

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What Wells are Good Candidates?What Wells are Good Candidates?Low hanging fruitLow hanging fruit--single stage openhole single stage openhole

lateralslaterals

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What Wells are Good Candidates?What Wells are Good Candidates?Low hanging fruitLow hanging fruit--single stage openhole single stage openhole

lateralslateralsNext rungNext rung--wells with limited number of wells with limited number of

stages where increased staging has resulted stages where increased staging has resulted in significant production improvementin significant production improvement

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What Wells are Good Candidates?What Wells are Good Candidates?Low hanging fruitLow hanging fruit--single stage openhole single stage openhole

lateralslateralsNext rungNext rung--wells with limited number of wells with limited number of

stages where increased staging has resulted stages where increased staging has resulted in significant production improvementin significant production improvementHigher rungHigher rung--poor performing clusters poor performing clusters

within stages within stages

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What Wells are Good Candidates?What Wells are Good Candidates?EconomicsEconomics--use offsets completed with use offsets completed with

current “best practices”current “best practices”--Bakken Bakken example example

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What Wells are Good Candidates?What Wells are Good Candidates?ChallengesChallenges--fraccing fraccing candidates that are candidates that are

currently still economic and getting crewscurrently still economic and getting crews

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RefracRefrac Treatment OptimizationTreatment OptimizationDFIT ACA* permeability is the critical DFIT ACA* permeability is the critical

inputinputIdealIdeal--vertical pilot well with external casing vertical pilot well with external casing

DTS fiber optic array for frac heightDTS fiber optic array for frac height--need to get need to get h from DFITh from DFIT khkh

* Diagnostic Fracture Injection Test After Closure Analysis* Diagnostic Fracture Injection Test After Closure Analysis

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RefracRefrac Treatment OptimizationTreatment OptimizationData suggests the key variable is the spacing Data suggests the key variable is the spacing

between dominant fractures in each stage between dominant fractures in each stage not cluster or stage spacingnot cluster or stage spacingAssume frac spacing = stage spacingAssume frac spacing = stage spacing

Cluster perforatingCluster perforating--highly inefficient and highly inefficient and unpredictable resultsunpredictable results--difficult to difficult to refracrefracSingle cluster frac stages outperform Single cluster frac stages outperform

multiple clusters theoretically and multiple clusters theoretically and empiricallyempirically

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Single Single vsvs Multiple ClustersMultiple Clusters

*Gord Mayr Apache Horn River May 2011 SPE Tight Reservoir Completions WS Banff

Multiple cluster average 2.7 clusters/stage this studyIndustry average 4-5 clusters/stage

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Single Single vsvs Multiple ClustersMultiple Clusters

*Gord Mayr Apache Horn River May 2011 SPE Tight Reservoir Completions WS Banff

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Vertical Well Multiple Cluster StagesVertical Well Multiple Cluster StagesMultiple Zone Stage Multiple Zone Stage Single Zone StageSingle Zone Stage

Xf Xf ApparentApparent

259 ft 259 ft 269ft269ft

1ft1ft

1ft1ftOne of multiple zones perforated (primary frac):One of multiple zones perforated (primary frac):Identical to single perforated interval frac stageIdentical to single perforated interval frac stage

Secondary Secondary fracsfracs: Skin removal only: Skin removal onlyHorizontal wellsHorizontal wells--exacerbated with stress shadowingexacerbated with stress shadowing

Barba and Shook SPE 90483Barba and Shook SPE 90483

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Horizontal Well Stress ShadowingHorizontal Well Stress Shadowing

Vertical wellsVertical wells--no significant stress shadowing affecting clustersno significant stress shadowing affecting clustersHorizontal stress shadowingHorizontal stress shadowing--harder to stimulate >1 clusterharder to stimulate >1 cluster

SPE 131732 Meyer&SPE 131732 Meyer&JacotJacot, SPE 125526 Britt&Smith, SPE 90051 Fisher, SPE 138843 Cheng, SPE 125526 Britt&Smith, SPE 90051 Fisher, SPE 138843 Cheng

H 250-300 ftEFS/Marcellus/HV

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Typical Horizontal Shale PLTTypical Horizontal Shale PLT

One cluster out of five producingOne cluster out of five producing--same for 6 of 7 stages SPE 131732same for 6 of 7 stages SPE 131732

SchlumbergerSchlumberger 200 well study200 well study--80% of PLT gas from 20% of 80% of PLT gas from 20% of perfsperfs

Stress shadowingStress shadowing--all all perfs perfs within twice the frac height affectedwithin twice the frac height affected

For For refracsrefracs--which cluster was fracced?which cluster was fracced?

SPE 131732 Meyer and SPE 131732 Meyer and JacotJacot

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Gas Shale DFIT PermeabilityGas Shale DFIT Permeability

Meyer and Yeager SPE 139067Meyer and Yeager SPE 139067

Maximum average permeability published: 500 Maximum average permeability published: 500 ndnd

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Optimum Frac Spacing Optimum Frac Spacing vsvs PermPerm

Spac

ing

Bet

wee

n Fr

actu

res

ftSp

acin

g B

etw

een

Frac

ture

s ft

SPE 131732SPE 131732

180 ft frac spacing for 500 180 ft frac spacing for 500 nd nd rockrock--no published gas shale cases with higher permsno published gas shale cases with higher perms5000 ft lateral with 180 ft spacing=28 frac stages5000 ft lateral with 180 ft spacing=28 frac stagesOil Oil shalesshales--tighter spacing due to lower mobilitytighter spacing due to lower mobility

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Trajectory Trajectory vs vs Propped HeightPropped Height 3D simulations and well performance analysis 3D simulations and well performance analysis

suggest there is excessive proppant settling with suggest there is excessive proppant settling with the slick water systemsthe slick water systems

3D simulations3D simulations--45 ft of proppant bank above base 45 ft of proppant bank above base of Marcellusof Marcellus

Atlas DUG East 2010Atlas DUG East 2010--wells with more stages in wells with more stages in proppant bank outperformed those with fewer proppant bank outperformed those with fewer stages in bankstages in bank

Numerous operatorsNumerous operators--similar observations and similar observations and “best practices” = lower trajectories“best practices” = lower trajectories

2245 ft of propped height45 ft of propped height--200,000 lb 100 mesh 300,000 lb 40/70 white200,000 lb 100 mesh 300,000 lb 40/70 white

Marcellus SPE Example

0 1000 2000 3000 4000 5000 6000 7000

Length (ft)

mD-ftmD-ft01002003004005006007008009001000

Stress

5000 6000 7000 8000

Stress (psi)

7830

7840

7850

7860

7870

7880

7890

7900

7910

7920

TVD

(ft)

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Marcellus Trajectory ExampleMarcellus Trajectory Example

Wells A&B 5Wells A&B 5--6 MMCFD IP, Well C 1.5 MMCFD6 MMCFD IP, Well C 1.5 MMCFDOrange=3D frac model propped height Greene County PaOrange=3D frac model propped height Greene County Pa

Base MarcellusBase Marcellus8 of 9 stages in proppant bank

9 of 9 stages in proppant bank

7 of 11 stages in proppant bank

Henry Henry Jacot Jacot Dug East 2010Dug East 2010

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High Modulus Proppant “Wedge”High Modulus Proppant “Wedge”

High modulus BarnettHigh modulus Barnett--strong evidence ofstrong evidence of unproppedunpropped heightheightLow modulus rockLow modulus rock--unproppedunpropped frac closes with frac closes with drawdowndrawdown

EFS, Haynesville, and MarcellusEFS, Haynesville, and Marcellus--much lower modulusmuch lower modulusBritt and Britt and Schoeffler Schoeffler SPE 125525SPE 125525

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RefracRefrac Zone Isolation IssuesZone Isolation Issues

Ideal configuration for new wellsIdeal configuration for new wells--cased cemented cased cemented perforated or notched completion with openhole perforated or notched completion with openhole packer type system set in casingpacker type system set in casing

Single Single perfperf cluster stagescluster stages--rate down 2 7/8 flush rate down 2 7/8 flush joint tubing should be adequate (20joint tubing should be adequate (20--25 25 bpmbpm))

Stages with poor performanceStages with poor performance--can set plug below can set plug below target stage, close sleeves between heel and target target stage, close sleeves between heel and target stage, refracture target zone stage, refracture target zone

Following Following refrac refrac all sleeves can then be reall sleeves can then be re--openedopened

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Can Offset Wells Drain the Gaps?Can Offset Wells Drain the Gaps? If stages are too far apart can the gas If stages are too far apart can the gas

inbetween inbetween the drainage patterns be the drainage patterns be effectively recovered?effectively recovered?Where did the existingWhere did the existing fracsfracs initiate? (PLT?)initiate? (PLT?)What pattern did the offset What pattern did the offset fracs fracs drain?drain?Did stress shadowing affect the drainage Did stress shadowing affect the drainage

azimuth?azimuth?

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Stress Shadowing vs Azimuthhmax

Stages selected from mud log showsStages selected from mud log showsand to avoid lost circulation zones from offsetsand to avoid lost circulation zones from offsets

Fracced into depletion on 3Fracced into depletion on 3rdrd and 5and 5thth stagesstages

Max stressdistributionaffected by

previous fracstage

Lower Spraberry 1988SPE 19721 and 23949

VerticalOffset Well

VerticalOffset Well

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Poor Performing Stage RepairPoor Performing Stage Repair Stages with poor initial connection to fracStages with poor initial connection to frac--refrac refrac

with higher viscosity fluidwith higher viscosity fluid Hybrid foam probably better choice than linear or Hybrid foam probably better choice than linear or

crosslinked crosslinked gelgel Foams have less water and less gel and should be Foams have less water and less gel and should be

less damaging than gelled waterless damaging than gelled water Initiating with lower viscosity may increase Initiating with lower viscosity may increase

complexity and length complexity and length vsvs pumping high viscosity pumping high viscosity stable foam entire jobstable foam entire job

New fiber “Highway Frac” promising initial New fiber “Highway Frac” promising initial resultsresults--is it from reduction of settling or “pillars” is it from reduction of settling or “pillars” as advertised?as advertised?

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Isolating Existing PerforationsIsolating Existing PerforationsNumerous options available to seal off Numerous options available to seal off

existing existing perfs perfs and start and start refracs refracs with a new with a new wellbore:wellbore:Enventure Enventure expandable linerexpandable linerWeatherford “Weatherford “MetalskinMetalskin””Core Lab “Core Lab “Pengo Pengo Patch”Patch”Openhole “Packers Plus” systems in casingOpenhole “Packers Plus” systems in casingSeveral other options from other vendorsSeveral other options from other vendors

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Enventure Enventure Expandable LinerExpandable Liner

Dave Mayhall presentation May 2011 SPE Tight Reservoir Completions WS Banff

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Possible New Well ConfigurationPossible New Well Configuration

Single perforation cluster stagesSingle perforation cluster stages--notched or notched or hydrajetted hydrajetted for low for low tortuositytortuosity

Frac current number of stages at spacing for 500 Frac current number of stages at spacing for 500 ndnd permeability (180 ft) permeability (180 ft)

Frac remaining lateral length at later date as technology improvFrac remaining lateral length at later date as technology improveses

What is PUD status of remaining lateral length? Same as offset lWhat is PUD status of remaining lateral length? Same as offset locations??ocations??

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ConclusionsConclusions Current and previous industry stage and cluster Current and previous industry stage and cluster

spacing practices are probably resulting in spacing practices are probably resulting in significant significant undrained undrained reservoir volumes with reservoir volumes with excellent refracture potentialexcellent refracture potential

Numerous current industry completion practices Numerous current industry completion practices have limitations that should be overcome with the have limitations that should be overcome with the inevitable learning curveinevitable learning curve

Operators should build flexibility into their current Operators should build flexibility into their current completions to better capture the potential upside completions to better capture the potential upside from this learning curvefrom this learning curveOptimize stage spacing based on permeabilityOptimize stage spacing based on permeability Frac distal part of wellbore using this spacingFrac distal part of wellbore using this spacing