Perforation Inflow Diagnostics · perm reservoir pressure reservoir pressure perm perm perm reservoir pressure perm perm reservoir pressure reservoir pressure We’ll test it after

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Pre-frac Reservoir Characterization from

Perforation Inflow Diagnostic (PID) Testing

“Measure Twice – Frac Once”

Robert HawkesTeam Leader, Reservoir Services

BJ Services Company Canada

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SPE DISTINGUISHED LECTURER SERIES

is funded principallythrough a grant of the

SPE FOUNDATIONThe Society gratefully acknowledges

those companies that support the programby allowing their professionals

to participate as Lecturers.

And special thanks to The American Institute of Mining, Metallurgical,and Petroleum Engineers (AIME) for their contribution to the

program.

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EXECUTIVE SUMMARYEXECUTIVE SUMMARY

Initial post-frac welltest analysis OVER-ESTIMATE most tight gas well production performances.

Take the time (money) to obtain initial reservoir pressure (pi) prior to your fracture treatment.

Closed chamber testing is an overlooked pre-frac testing technique.

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ProblemProblemWe have completed our hydraulic fracture treatment program with most wells on production.

Post frac pressure buildup analysis are finished.

Initial production results are less than what we predicted.

Please review the frac treatment reports and the well test analysis to determine re-frac candidates !

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General PTA TheoryGeneral PTA Theory

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Time to End of Linear FlowTime to End of Linear Flow

Where the end of linear flow from a fracture is defined as tDxf =0.016

hourstxckt

tfit

Dxf == 2)(000264.0μφ

k = 0.1 mD xf = 100m t = 36 h (1.5 d)

k = 0.01 mD xf = 100m t = 360 h (15 d)

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from Economides and Martin (2007)

LogLog--log Plot (Linear Flow) log Plot (Linear Flow)

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Production AnalysisProduction Analysis

The Fetkovich plot is to production analysis what the log-log derivative is to the well test analysis.

mL = -½

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PostPost--frac Flow and Buildup Testfrac Flow and Buildup Test

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150

Time, h

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

16000

17000

18000

19000

Pres

sure

, kPa

(a)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

Gas R

ate, 103m

3/d

Total TestENCANA CORPORATION.ECA SMOKY 7-21-59-4W6

UPPER BELLY RIVER : 2087.5 - 2092.5 mKB.2005/06/13 TO 2005/06/18.

pdataqgas

Δ t 107.54 hpdata 17916 kPa(a)

30 Tonnes, 20/40 Ottawa Type Sand

92 m3 Gelled Hydro-Carbon, 15 m3 CO2

Max sand concentration 900 kg/m3

Frac gradient ~ 14.8 kPa/m

30 Tonnes, 20/40 Ottawa Type Sand

92 m3 Gelled Hydro-Carbon, 15 m3 CO2

Max sand concentration 900 kg/m3

Frac gradient ~ 14.8 kPa/m

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10-1 1.0 101 1022 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 2 3 4 5 6 7 8 9

Pseudo-Time, h

1.0

101

2

3

4

56

8

2

3

4

56

8

2

3

4

56

8

Δψ

/ D

eriv

ativ

e, 1

06kP

a2/μ

Pa.s

Log log PlotENCANA CORPORATION.ECA SMOKY 7-21-59-4W6


ΔψdataDerivativedata

Storage 1

Radial 0


False Radial Flow.

Where’s the Frac?!!

Note the very early flattening of the pressure derivative (1.0 h).

False Radial Flow.

Where’s the Frac?!!

Note the very early flattening of the pressure derivative (1.0 h).

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1011021032345678923456789234567823456789

Superposition Radial Pseudo-Time (ΣΔ ta), h

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

ψ, 1

06kP

a2/μ

Pa.s

0300040005000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

16000

17000

18000

19000

p, kPa(a)

Horner PlotENCANA CORPORATION.ECA SMOKY 7-21-59-4W6


ψdata

Analysis 1p* 18583 kPa(a)kh 0.90 mD.ms' -2.865

Δ t 105.92 hp 17906 kPa(a)

Results:

pr = 18585 kPa

kh = 0.9 mD.m

s = -2.9

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Trapped injected fluid

An Idealized View Of A Propped An Idealized View Of A Propped Fracture Showing Trapped Fluid Fracture Showing Trapped Fluid Due To High Capillary End EffectsDue To High Capillary End Effects

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permreservoirpressure

reservoirpressure

perm

perm

perm

reservoirpressure

perm

permreservoirpressure

reservoirpressure

We’ll test it after the

frac

reservoirpressure

Good Tests Cost Money; Good Tests Cost Money; Bad Tests Cost MOREBad Tests Cost MORE

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Concept of Tight Gas Concept of Tight Gas Deliverability BehaviourDeliverability Behaviour

Flush Production

COMPLETIONEFFECTIVENESS

Stabilized Production

RESERVOIRCHARACTERISTICS

Deliverability

The completion controls Flush production, were as the reservoir controls Stabilized production

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Concept of Tight Gas Concept of Tight Gas Deliverability BehaviourDeliverability Behaviour

Gas

Rat

e

Time

Flush Production

Flush Production:cont rolled by Reservoir Pressure (pi),f low capacity (kh)and, complet ion effect iveness (xf).

Long Term Production:controlled by flow capcity (kh) drainage area and shape (A).

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Reservoir CharacteristicsReservoir CharacteristicsFlow Capacity (kh)

biggest impact on a well’s deliverabilitysystem kh?

Net Pay (h)a moving target.storage driven?deliverability driven?

Effective Porosity (ø)all pores are NOT created equal

logs (static)cores (needs to be corrected)welltest (dynamic)production (ground truth?)

cut-off (???)permeability or storage?gas saturationporosity

logsCores (mineralogy!!)material balance

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Completion EffectivenessCompletion Effectiveness

An Fcd of 1.6, is the optimum for ANY reservoir, well, and proppant.

In low permeability formations, this requirement results in a long and narrow fracture.

kf frac permwf frac widthkm matrix permxf frac half−length

ˆUnified Fracture Design˜, Economides, Michael J, et al 2002.

In high permeability formations, a short and wide fracture provides the same Fcd.

fm

ffCD xk

WkF

•

•=

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Optimum Dimensionless Optimum Dimensionless Fracture ConductivityFracture Conductivity

An accurate knowledge of the formation permeability is essential

More important than anything else

Unfortunately, fracture permeability (kf ) is not constant for gas wells

Non-Darcy flow effectsMultiphase flow effects

Therefore design for Fcd of 20

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Township 078-11W6

01-28

08-2805-27

12-27

14-2716-27

10-27

08-27

04-26

13-23

01-27

02-27

14-22

METERS

0 600

PETRA 2007/01/09 11:42:39

100T Water 100T Water Based FracsBased Fracs

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PRODUCTION DIAGNOSTICS

1

10

100

1 10 100 1000

OPERATING TIME (DAYS)

GA

S R

ATE

(E3M

3/D

)

Well : 01-27 Well : 02-27

Frac Model (S = -5.7)

GIP = 14.0 E3 m3

Pr = 23,000 kPa

kh = 0.55 mD.m

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1

10

100

1 10 100 1000


GA

S R

ATE

(E3M

3/D

)

Well : 01-27 Well : 02-27

Frac Model (S = -2.3)

GIP = 14.0 E3 m3

Pr = 23,000 kPa

kh = 0.55 mD.m

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1

10

100

1 10 100 1000


GA

S R

ATE

(E3M

3/D

)

Well : 01-27 Well : 02-27

Frac Model -5.7 KH Model

GIP = 14.0 E3 m3

Pr = 23,000 kPa

kh = 0.55 mD.m

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Sensitivity of Production ForecastSensitivity of Production Forecast

10%

26%

0%

7%

2%1%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Pr kh A Xf Sf Kw f

% Error in Cum G as Forecast

30% error in param eters5% error in reservoir pressure

Com pletion Effectiveness

Reservoir Characteristics

30% error in kh estimate results in a 26% error in cum gas forecast.

30% error in frac length is only 7% error in cum gas forecast.

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))()(/()

43(ln1422

wfavg

w

epmpmq

srrT

khJ −=+−

=

[ ][ ] [ ]qb

ssq

a

ba ×

++

=88

In the rule of eights, sb and sa represent the skin effects before and after fracture treatment, respectively. Similarly qb and qa represent the boundary-dominated flow rates before and after fracture treatment, where….

fw xr21

=′

sww err −=′ )/ln( ww rrs ′−=or

)8( skhJ+

=

Productivity Index (J ) can be expressed in the following terms:

In it’s simplified form, it can be expressed as:

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What is PID testing ?What is PID testing ?

Perforation Inflow Diagnostics (PID).

Pre-frac reservoir test.

Underbalanced perforating procedures.

Application of closed chamber testing .

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3 Month Window for3 Month Window forDrilling and Completions in CanadaDrilling and Completions in Canada

December 30th

March 30th

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PID Theory PID Theory

Closed Chamber EquationClosed Chamber Equation

( )dtpd

pCq www 24=

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PID Testing for Shallow Gas

• Cost effective.• Rigless.• Evacuated wellbore.• Electronic surface

recorders.• multi-zone reservoirs.

SURFACE ELECTRONICPRESSURE RECORDERS

Surface Pressure Data Logger

Shallow Gas Operation Shallow Gas Operation

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0

500

1000

1500

2000

2500

3000

3500

4000

0 2 4 6 8 10 12 14 16 18

Time (Hrs.)

Pre

ssur

e (k

Pa)

0

1

2

3

4

5

6

7

8

Gas

Flo

w R

ate

(10^

3 m

3/d)Ellerslie perforations: 1265.0-1269.5 mKB

Surface pressures converted to sandface

Perf Well

Calculated gas rate

Pressure

( )dtpd

pCq www 24=

Closed Chamber TheoryClosed Chamber Theory

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0.0001

0.001

0.01

0.1

1

10

0.0001 0.001 0.01 0.1 1 10 100

Pseudo Time

Pseu

do P

ress

ure

and

Der

ivat

ive

Ellerslie perforations: 1265.0-1269.5 mKB

-1 slope

StoragePseudo Pressure

Derivative

t = 2.1 hrs

LogLog--log Derivative Plotlog Derivative Plot

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Inverse Time Plot

0.6

0.7

0.8

0.9

1

1.1

1.2

00.511.52Inverse Pseudo Time

Pse

udo

Pre

ssur

e


p*=3431 kPa

t = 2.1 hrs

Inverse Time Plot

1/Δta

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1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Rate Conv. Fn.

p(pn

) (kP

a)

S = .5S = 3S = 5.5Slope


kh = 7.5 mD.mS = +3.0

t = 2.1 hrs

t = 0.7 hrs

( ) ( )⎟⎟⎠

⎞⎜⎜⎝

⎛+Σ+=−

qstqtmpp

refnwsi

~log

Rate Convolution Semilog PlotRate Convolution Semilog Plot

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Radius of Investigation with Radius of Investigation with respect to PID Testingrespect to PID Testing

if Cores investigate “inches”,

Logs investigate “feet”,

Well Tests investigates“hundreds of feet”,

as long as you can measure a change in pressure, you areeffectivelyeffectively flowingflowing the well.

Radius of Investigation (ri) is based on time (t) and permeability (k), not flow rate.

ti c

tkr××Φ×

×=

μ44.69

Surface Pressure Data Logger

Recorders on Recorders on PerfPerf Gun Operation Gun Operation

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Overlay Of Overlay Of PerfgunPerfgun Recorders and Surface RecordersRecorders and Surface Recorders

Both surface and BHP gauges were used to monitor the inflow response after perforating the well.

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Overlay Of Overlay Of PerfgunPerfgun Recorders and Surface RecordersRecorders and Surface Recorders

The expanded scale of this plot shows a 4 minute delay in gas inflow after perforating the Vikng.

ERHSC 86.0 mm

25 gr SDP

5 SPF 60°

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VIKING : 746.5 - 747.5 mKB.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Time (Hrs.)

Pres

sure

(kP

a)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Gas

Flo

w R

ate

(10^

3 m

3/d)

PQsc(N)

AOF = 3.5 103m3/d

Gas rates was calculated using the closed chamber technique based on a gas chamber volume of 5.3 m3.

Closed Chamber TheoryClosed Chamber Theory

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VIKING : 746.5 - 747.5 mKB.

100000

1000000

10000000

100000000

0.0001 0.001 0.01 0.1 1 10

Qsc Norm (10^3 m3/d)

Pr^2

- Pw

^2 (k

Paa

^2) The inverse slope (n) of 1.0

is characteristic of dry gas (laminar) inflow.

n= 1.0

Back Pressure PlotBack Pressure Plot

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PID Testing for Deep, Tight Gas

Cost effective, safe.Electronic downhole recordersDownhole shut-inTwo days rig time

SURFACE ELECTRONICPRESSURE RECORDERS

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Downhole Gauge

Plug w/recorders

dp/dt

Build up

Set Csg Plug

Tight Gas PID TestTight Gas PID Test

Time

Pre

ssur

e

Perforation

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RRD @2070.0 mkB

PID TestPID Test

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10-3 10-2 10-1 1.0 101 1022 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4 5 6 7 8

Δta , h

10-2

10-1

1.0

101

2

3

45

79

2

3

45

79

2

3

45

79

Δψ

/ De

rivat

ive

, 106

kPa2

/μPa

.sENCANA CORPORATION. ECA SMOKY 7-21-59-4W6 UPPER BELLY RIVER 2087.5 - 2092.5 mKB. 2005/06/10 to 2005/06/11.

Δψ / DerivativedataDerivativedata

Storage 1

Slope -1

Δ t 11.05 hp 18456 kPaThe derivative response of -1

reflects radial flow.

PID TestPID Test

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0.000.020.040.060.080.100.120.140.160.180.200.220.240.260.280.300.320.340.360.380.400.420.440.460.480.500.520.540.56

1 / Δta , hr-1

20.00

20.50

21.00

21.50

22.00

22.50

23.00

23.50

24.00

24.50

25.00

25.50

26.00

26.50

27.00

27.50

28.00

28.50

29.00

ψ, 1

06kP

a2/μ

Pa.

s

15800

16000

16200

16400

16600

16800

17000

17200

17400

17600

17800

18000

18200

18400

18600

18800

19000

19200

19400

19600

p , kPa

ENCANA CORPORATION. ECA SMOKY 7-21-59-4W6 UPPER BELLY RIVER 2087.5 - 2092.5 mKB. 2005/06/10 to 2005/06/11.

ψdata

Analysis 1p* 19174 kPa

Δ t 11.05 hp 18456 kPa

RRD @2070.0 mKB.

Expanded scale of the Impulse Plot

PID Test PID Test –– Inverse Time PlotInverse Time Plot

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1011021032345678923456789234567823456789

Superposition Radial Pseudo-Time (ΣΔ ta), h

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

ψ, 1

06kP

a2/μ

Pa.s

0300040005000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

16000

17000

18000

19000

p, kPa(a)

Horner PlotENCANA CORPORATION.ECA SMOKY 7-21-59-4W6


ψdata



If we honour the reservoir pressure obtained from the PID test:

p* increases by 3%

kh reduces by 55%


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Importance of InitialReservoir Pressure

14 Day Buidlup

240 Day Buildup

Error %

pi [kPa] 19041 19293 1.3k [mD] 0.05 0.02 150xf [m] 40.1 66.2 39kf.w [mD.m] 280 470 40

5 yrs. ΔG [MMscf] 100 65 54

CASE HISTORY*

* Hategan and Hawkes, 2006

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ConclusionsConclusions

Initial post-frac buildup analysis OVER-ESTIMATE most tight gas well production performances.

Perforation Inflow Diagnostic (PID) Analysis gives us the ability to peer through the wellbore region and determine the quality of the reservoir rock lurking behind.

SPEDL Series

ConclusionsConclusions

Closed chamber testing during underbalanced perforating is an overlooked pre-frac testing technique to determine initial reservoir pressure and in-situ permeability.

In tight gas reservoirs, reservoir pressure is a critical parameter for hydraulic fracturing treatments and evaluation.

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“It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts”

Sherlock Holmes

Documents

Perforation Inflow Diagnostics · perm reservoir pressure reservoir pressure perm perm perm reservoir pressure perm perm reservoir pressure reservoir pressure We’ll test it after