The SPE Foundation and member donations primarily fund the SPE Distinguished Lecturer Program. Companies also support the program by allowing employees to serve as lecturers. Additional support comes from AIME. The program provides 30 minute presentations on reservoir topics. Robert Hawkes will present on hydraulic fracture flowback dynamics, discussing load fluid recovery and its implications for long term production. His presentation will cover laboratory observations, field data, and diagnostic tools to understand flowback mechanisms and estimate ultimate load fluid recovery.

1. Primary funding is provided by
The SPE Foundation through member donations
and a contribution from Offshore Europe
The Society is grateful to those companies that allow their
professionals to serve as lecturers
Additional support provided by AIME
Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl

2. Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl
Robert Hawkes
Manager Reservoir Services
Fluid Imbibition ‐ Hydraulic Fracture
Flowback Dynamics
Calgary, Sept 20 2018
30 min presentation

3. What is YOUR idealized
hydraulic fracture result:
100% Load Fluid Recovery?
or
0% Load Fluid Recovery?
3
hydraulicProppedEffective
BazanConsulting Inc.
SPE DL, Potential Lecture, R.Hawkes

4. This is a LogLog
plot showing
CumGas vs
LFLTR after
Flowback.
BCOGC AOF Test Data (MNTN)
Load Fluid To Recover (LFTR), m3
CumGas, E3m3
4LFLTR: Load Fluid To Recover, m3

5. Outline
1. Properties of Unconventional Reservoirs
2. Laboratory Observations
3. Dynamic Field Observations
•Load Fluid Recovery Diagnostics
4. Summary and Comments
SPE DL, 2018‐19 R.Hawkes 5

6. Properties of Unconventional Reservoirs
6
Ultra‐low‐permeability rock, including
sandstone, siltstone, shale, and carbonates.
Sub‐irreducible state and organically rich.
Requires a great amount of fracturing fluid to
create multiple fractures to increase wellbore and
reservoir contact.
SPE DL, 2018‐19 R.Hawkes

7. Where did all the Frac water go?
……and what are the implications to long term production?
7SPE DL, 2018‐19 R.Hawkes
Why do some wells Flowback less load fluid?
Does extended shut‐in time improve
hydrocarbon productivity?

8. 8
In one corner of the ring, there
is the conventional practice to
minimize the occurrence and
length of production delays and
shut‐ins.
Production Delays and Extended Shut‐ins
What is an engineer to do?
In the other corner, we have
the slickwater operators
without any particular best
practices for flowback, with
apparently no detrimental
consequences to production.
SPE DL, 2018‐19 R.Hawkes
Flowback as
soon as possible
Take your Time

9. Day/Month
SOAKBACK
SLOWBACK
FASTBACK
Frac Job ProductionShut-In
Modified from SPE 166279
???
1 2 5 10 - 365
9
Hydraulic Fracture Flowback Dynamics
SPE DL, 2018‐19 R.Hawkes

10. 10
Soak
Time
Functional Dependent Parameters
• Spontaneous
Imbibition
• Wettability
• IFT
• Clay Type
• Chemical
Osmosis
• Total Organic
Content
• SWir
• Rock Fabric
Rock Fabric Drivers to
Observed Flowback Dynamics
SPE DL, 2018‐19 R.Hawkes

11. Key Observations
In the Laboratory
11SPE DL, 2018‐19 R.Hawkes

12. Obs 1: Water Imbibition and Salt Diffusion
Conductivity Meter
Gas Shale Sample
Deionized Water
Ion Transport Direction
Water Transport Direction
SPE-167165
Counter‐current Imbibition

13. Chemical Osmosis
• As water is a polar molecule,
the NaCl in water causes the Na
and Cl to have six polar water
molecules surrounding them
increasing their hydration
diameters (Conway, 1981).
• The space between the illite
sheets is small enough to allow
water to move through but not
Na and Cl with six polar
molecules attached and this
creates a semi permeable
membrane to fresh water but
not to salty water.
SPE DL, 2018‐19 R.Hawkes 13
Obs 1: Water Imbibition and Salt Diffusion

14. Obs 1: Water Imbibition and Salt Diffusion
(Shale Gas, Horn River Basin, B.C.)
SPE-167165
Salt DiffusionWater Imbibition
14SPE DL, 2018‐19 R.Hawkes

15. Obs 1: Water Imbibition and Salt Diffusion
(Shale Gas, Horn River Basin, B.C.)
Fort Simpson Muskwa Otter Park
0 Hours
52 Hours
Cracks
2.4 cm
Cracks
Cracks
SPE-167165
15SPE DL, 2018‐19 R.Hawkes

16. Obs 2: Salinity‐Dependent Imbibition
(Bakken Case Study)
SPE-168998
Low-salinity solutionHigh-salinity solution
Soak Time: 5 d Soak Time: 6 d
16SPE DL, 2018‐19 R.Hawkes

17. 17
3) Oil is expelled
due to osmotic‐
pressure increase
1) Initially, oil
occupies most of
the pore space
while formation
water is bound to
the clay platelets
2) Low‐salinity (slick
water frac fluid) flows
into clay structure
due to osmotic force.
Oil
Low‐salinity solution
High‐salinity solution
Obs 2: Salinity‐Dependent Imbibition
(Bakken Case Study)
SPE-168998
SPE DL, 2018‐19 R.Hawkes

18. 18
Obs 3: Mixed Wettability (Montney Core)
Water Oil
Time Time
SPE DL, 2018‐19 R.Hawkes University of Alberta

19. 19
•Montney Drill
cuttings
•Pre‐soak
cuttings in oil
for 5 days
•Placed in
surfactant
solution
FracFluid
1
FracFluid
2
FracFluid
3
FracFluid
4
BLANK
Obs 4: Amott Cell Testing
SPE DL, 2018‐19 R.Hawkes

20. Flowback Dynamics
Day/Month
SOAKBACK
SLOWBACK
FASTBACK
Frac Job ProductionShut-In
???
1 2 5 10 - 365
SPE DL, 2018‐19 R.Hawkes

21. Fundamental Flowback Dynamics:
1. COMPACTION DRIVE
• Compaction drive represents the portion of flowback
recovery due to effective fracture pore‐volume as
closure pressure approaches
2. DEPLETION DRIVE
• Depletion drive represents the portion of flowback
recovery due to water drainage
3. HYDROCARBON DRIVE
• Hydrocarbon represents the portion of flowback
recovery due to gas/oil expansion as pressure drops
SPE 175143
21SPE DL, 2018‐19 R.Hawkes

22. 1. linear flow of single-phase
water
3. loss in productivity to
water during gas buildup
in fractures below critical
gas saturation
4. free gas flow initiates, linear
flow of water and gas occurs
to well with eventual gas
saturation stablization
horizontal well
2. desorption
pressure reached
SPE 176869
Adopted (CBM) Concept from Dr. Chris Clarkson, UofC
22
Hz Well
1. Frac
Treatment
2. Spontaneous
imbibition
3. Flowback
4 Hydrocarbon drive
FASTBACK SOAKBACK SLOWBACK
SPE DL, 2018‐19 R.Hawkes

23. 1
10
100
1000
10000
0.1 1 10 100 1000 10000
Wtr Rate, m3/d
MBTime, hr
Wtr Rate
Flowback Plot of Wtr Rate vs MB Time
m = ‐1.0
m = ‐1/2
Single phase water flow
23
MBTime =WtrCum
WtrRate
Adopted (CBM) Concept from Dr. Chris Clarkson, UofC

24. Flowback Dynamics – A Reservoir Simulation Perspective
24
Gas
Wtr
Time, days
IPTC 16896
SPE 171799
Water Rate
Sensitivity of Primary and
Secondary Fractures
IPTC 16896
Sensitivity of well
shut‐in, wettability.
Gas Rate
Time, days
Shut‐in Shut‐in
SPE 171799
Cum Load Recovery vs Time

25. SPE DL, 2018‐19 R.Hawkes 25
0
1000
2000
3000
4000
5000
6000
0 2000 4000 6000 8000 10000 12000
GasCumulative
Water (Load Fluid) Cumulative
Gas Cumulative vs Water (Load Fluid) Cumulative
Gas Cumulative (m3)
Flowback Dynamics – A Diagnostics Perspective
I argue that the best
diagnostics for
understanding rock
fluid interaction during
flowback, is to build
plots where the notion
of TIME plays no role.
Time is an
illusion

26. SPE DL, 2018‐19 R.Hawkes 26
0
1000
2000
3000
4000
5000
6000
0 2000 4000 6000 8000 10000 12000
CumGas,m3
Cum Water (Load Fluid)
Cumulative Gas vs Cumulative Water (Load Fluid)
Gas Cumulative (m3)
Flowback Dynamics – A Diagnostics Perspective
Extended shut‐in

27. Shale Gas
Horn River Basin
Field Observations
Source: National Energy Board
Horn River is a distant
cousin to the Barnett
Shale of Texas

28. Field Observations from Horn River Shales
0
50
100
150
200
250
300
350
400
450
500
0
500
1000
1500
2000
2500
3000
0 100 200 300 400
Time, hrs
Water Rate
Gas Rate
0.1
1
10
10 100 1000 10000
GWR(E3m3/m3)
Gas Prod. E3m3
“V-shape GWR trend”
28
Log Log PLot
Gas Rate, E3m3/d
SPE DL, 2018‐19 R.Hawkes
SPE 171636

29. 0.1
1
10
10 100 1000 10000
GWR(E3m3 /m3)
Gas Prod. E3m3
“V-shape GWR trend”
Flowback Dynamics
29SPE DL, 2018‐19 R.Hawkes
SPE 171636

30.  Early gas production is from free
gas saturation within the primary
fractures (spontaneous imbibition)
 The negative slope, is depletion of
free gas from primary fracture
network.
The change in flow regimes
signifies the onset of communication
between matrix and natural fracture
system.
Flowback Dynamics
0.1
1
10
10 100 1000 10000
GWR (Mm3 /m3)
Gas Prod. Mm3
“V-shape GWR trend”
30SPE DL, 2018‐19 R.Hawkes
SPE 171636

31. Estimating
Ultimate Load
Fluid Recovery
using Early
Flowback
Diagnostics
Montney Gas
Source: National Energy Board

32. 32
1
10
100
1000
10000
0 2,000 4,000 6,000 8,000 10,000
Wtr Rate, m3
CumWtr, m3
Harmonic Flowback Plot (Semilog)
WtrRate
GasRate
LFTR: 18,583
ULFR* = 51%

33. 33
1
10
100
1000
10000
0 2000 4000 6000 8000 10000
WtrRate, m3/d
CumWtr, m3
LFTR = 12,826 m3
ULFR* = 51%

34. 1
10
100
1000
10000
0% 10% 20% 30% 40% 50%
Water Rate, m3/d
Load Recovery, Fraction
Uppr MNTN Well Review
34
Prod Acct = 5%
Proving to be a
great model for
predicting Load
Fluid Recovery.
SPE DL, 2018‐19 R.Hawkes

35. Field Observation
Montney Tight Oil
Source: National Energy Board
30 Stage N2 Slick Water
50m (165 ft spacing)
100 tonne/stage
Injected 16,390m3
(103,100 bbl) of water

36. …late time
linear flow.
Montney Tight Oil
…early time
radial flow???
The early time radial flow (slope = 0) is an indicator of
false radial flow and insufficient treating fluid cleanup
during flowback masking the propped fracture due to
high fluid saturation around the wellbore.
Economides Martin, Modern Fracturing, 2007
Time, hr
(dt)d(DP)/d(DT), Derivative
SPE DL, 2018‐19 R.Hawkes 36
3 Month Buildup Test
Slope 0.0
Slope 0.5

37. 37
Montney Tight Oil
FL* = 40%
Depletion Drive
Load Fluid Flowback
Oil Production
SPE DL, 2018‐19 R.Hawkes
FL* = Load Fluid Recovered
Injected Fluid Volume

38. 38
Montney Tight Oil
Production after 3
month shut‐in
Load Fluid Flowback
Oil Production
SPE DL, 2018‐19 R.Hawkes
Depletion Drive
Hydrocarbon Drive

39. 39
Montney Tight Oil
Oil Production after 3
month shut‐in
Oil Production
SPE DL, 2018‐19 R.Hawkes
Cum Oil vs Cum Load Fluid
The
downward
curvature
is not a
typical
tight oil
behavior

40. SPE DL, 2018‐18, R.Hawkes 40
Curve A: No Moveable Formation
Water
Curve B: To Early to Tell
Curve C: Both load fluid and Formation
Moveable Water, or fluid‐rock
incapability.

41. Field Observation
West Duvernay
Shale
Source: National Energy Board
The Duvernay Shale is a
distant cousin to the
Utica Shale of NE USA

42. Load Fluid
Recovered: 22%
Csg Tbg
Shut‐in well
to run in
Tubing string
Oil
Rate
Gas
Rate
Water
Rate
DUVERNAY EXAMPLE: Flowback Test
42
Time, days

43. DUVERNAY EXAMPLE: Production Test (Apr ‐ Aug, 2015)
Open Well To
Production after a
6.5 Month Soak
Csg
Press
Tbg
Press
Wellhead Pressure, kPa
Oil
Rate
Gas
Rate
Water
Rate
43
Time, days

44. 1
10
100
1000
10000
0 1000 2000 3000 4000 5000 6000
Rate, m3/d
Cum Load Fluid, m3
Load Fluid Recovery Plot
Load Fluid Rate
Oil Rate
West DUVERNAY EXAMPLE
44SPE DL, 2018‐18, R.Hawkes
Flowback
FL* = 45%
FL* = Load Fluid Recovered
Injected Fluid Volume

45. West DUVERNAY EXAMPLE
45SPE DL, 2018‐18, R.Hawkes
Flowback Shut‐in for 6.5 Months
FL* = 45%
FL* = Load Fluid Recovered
Injected Fluid Volume

46. West DUVERNAY EXAMPLE
46
Flowback Soakback
Unexpected
Trend
SPE DL, 2018‐18, R.Hawkes
Flowback Soakback

47. Field Observation
East Duvernay
Oil Shale
Analogous to
Eagleford
Source: National Energy Board

48. East Duvernay Oil Shale Completion
Hz Multi‐Stage Fractured Wells
Construction Cased Hole –5.5” Csg
TVD 7,200 ft
Lateral Length 8,200 ft
# of Stages Early on 12 now > 55
Frac Method Plug ‘n’ Perf
Fluid Type Slick Water/Hybrid
Typical Fluid Vol 310,000 early on now >500,000 bbls
Typical Proppant 40/70, 1 – 2 lb/gal
48SPE DL, 2018‐18, R.Hawkes

49. 49
Cum Oil vs Cum Load Fluid Recovery
SPE DL, 2018‐18, R.Hawkes
ME: Micro‐emulsion Surfactant
NE: Non‐emulsifiers

50. 50
Cum Oil/Stage vs Cum Load Fluid Recovery
SPE DL, 2018‐18, R.Hawkes
 100% Load Fluid Recovery?
 0% Load Fluid Recovery?

51. 1. Flowback analysis can either be quantitative or qualitative,
depending on your a) tool box, b) assumptions and c) data set.
2. Soaking allows for dissipation of water into the matrix and un‐
propped fractures to help “suck‐in” the water and (can) allow
for higher peak hydrocarbon rates.
3. Construction of Load Fluid Recovery diagnostic plots helps in
understanding fluid‐rock interaction in unconventional
reservoirs.
Summary Comments
SPE DL, 2018‐18, R.Hawkes

52. Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl 52
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