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7/28/2019 Five Things Mike Vincent
1/19
Five things you didnt want to knowabout hydraulic fractures
Mike [email protected]
FracwellLLC
Microseismic image: SPE 119636
Why we need to frac The bad news
5 things you didnt want to know
The good news Compensating for some of these problems can
significantly improve production and profitability!
Outline
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Where Do we find Oil and Gas?
(NOT IN UNDERGROUND LAKES!) (NOT IN UNDERGROUND LAKES!)
Why Fracture Stimulate?
Top View
Side View
Unstimulated Wells:
Require high reservoirpermeability for sufficient
hydrocarbon flow
Hydraulic Fractures:
Accumulate hydrocarbonsover enormous area,achieving economicflowrates from low
permeability formations
Figures not to scale!
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Reservoir Contact
Multi-Lateral 15,000 ft of drilled length in 5 laterals
10,000,000 ft 2 >1,000,000m 2 of contact
Transversely Fractured Horizontal Wells let you Repeat this!
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Technology Progression
0.0001
0.001
0.01
0.1
1
10
0
1
10
100
1,000
10,000
100,000
1,000,000
CementedVertical
UncementedVertical
UncementedHorizontal
BiwingFracture
MultipleTransverse
Fractures
R e s e r v o
i r P e r m
m D
R e s e r v o
i r C o n
t a c
t m
2
Reservoir Contact
Economic Gas Reservoir PermEconomic Oil Reservoir Perm
Increasing our reservoir contact by 1,000,000 fold
has allowed pursuit of reservoirs with thousands of times lower perm
In low perm reservoirs, fractures are often the most critical component of our
completion
However, they are the most poorly optimizedelement!
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Fracs Simple (bi-wing), planar, vertical, hydraulically
continuous, highly conductive
Reservoir Homogenous reservoirs (or simplified layering)
Fluid Flow Simple fluid flow regimes
Convenient Assumptions
SPE 128612
Do we envision fracs correctly?
10
We picture fracs as perfect vertical planeswithout restriction to hydrocarbon flow
Fracs are very narrowribbons, massively long!Frac length frequently
thousands of times greater thanthe wellbore diameter
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500
1500
7000
182
1137
5715
72
672
3481
24
225
1243
549
479
1.4
14144
0.6 7130
0.3 496
0
1000
2000
3000
4000
5000
6000
7000
E f f e c
t i v e
C o n
d u c
t i v
i t y
( m d - f
t ) ( D - m
)
API Test Modified 50-Hour Test
"InertialFlow" withNon-Darcy
Effects
LowerAchievedWidth (1lb/sq ft)
MultiphaseFlow
50% GelDamage
FinesMigration /Plugging
CyclicStress
Chinese Sand
Jordan Sand
CarboLITE
Realistic Conductivity Reductions20/40 proppants at 6000 psi
0.3
0.6
0.9
1.2
2.1
1.5
1.8
0.0001 D-m
0.001 D-m
0.029 D-m
Conditions: YM=5e 6 psi, 50% gel damage, 250 F, 1 lb/ft 2, 6000 psi, 250 mcfd, 1000 psi bhfp, 20 ft pay, 10 blpdYM=34e 3 MPa, 50% gel damage, 121C, 5 kg/m 2, 41 MPa, 7000 m 3 /d, 7 MPa bhfp, 6 m pay, 1 .6 m 3l/d
References: ST Sand: SPE 14133, 16415, CL: Carbo typical, LT: Stim-Lab PredK 2002, SPE 24008, 3298, 7573, 11634, CARBO Tech Rpt 99-062, Run #6542, StimLab July 2000, SPE 16912, 19091, 22850, 106301, 84306
Effective conductivities can beless than 1% of API test values
99.9%reduction
99.7%reduction
98.6%reduction
11
Does Conductivity Degrade? McDaniel , SPE 15067
All published lab data show proppantscontinue to crush, compact, rearrange over
time and lose conductivity.
SPE 12616, 14133, 15067, 110451,128612,134330, 136757, Hahn, Drilling Vol 47, No 6,
April 1986
Some proppants are more durable thanothers. But none are constant
Why dont engineers recognize this?
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Pollard (2005) Northeast Ship Rock Dike, New Mexico13
Relatively simple, extremely wide fracture
Extends 9500 feet atsurface, average widthexceeding 7 feet!
We have created hydraulic
fracs 2200 ft half-length butless than 0.1 inches wide
Pollard (2005) Northeast Ship Rock Dike14
Outcrop actually comprised of >30 discrete echelon segments separated by intact host rock
Even this dike appeared discontinuous in outcrop.Are you certain your frac is continuous?
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NEVADA TEST SITE - HYDRAULIC FRACTURE MINEBACK
Observations of Fracture Complexity
Physical evidence of fractures nearly always
complex
Multiple Fractures
Initiation At Perforations Multiple Perforations
Provide Multiple EntryPoints For FractureInitiation
Five SeparateFractures Are VisibleIn These FracturesInitiated FromHorizontal Wellbore
12 Perforations Total 6 Top & Bottom
I would have modeled/predicted a single frac with muchhigher conductivity than 5 narrow fracs added together
[This actually is a bad outcome!]
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7/28/2019 Five Things Mike Vincent
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NEVADA TEST SITEHYDRAULIC FRACTURE
MINEBACK
Multiple Strands in a Propped Fracture
(Vertical Well)
These fractures are narrow, you are lookingat an angle to the exposed frac face
Mesaverde MWX test, SPE 22876
Physical evidence of fractures nearly always
complex
Multiple Strands in a Propped Fracture (Vertical Well)
7100 ft TVD [2160m]32 Fracture Strands Over 4 Ft Interval
HPG gel residue on all surfacesGel glued some core together (>6yrs elapsed post-frac!)All observed frac sand (20/40RCS) pulverized
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Is complexity
solely attributed to rock fabric?
Many other examples! [TerraTek, Baker, Weijers, CSM FAST consortium]
Unconsolidated 200 mesh sand, 35 lb XLG,Flow SPE 63233
Chudnovsky, Univ of Ill, Chicago
19
Physical evidence of fractures nearly always complex
NEVADA TEST SITEHYDRAULIC FRACTURE
MINEBACK
Fracture Complexity Due To Joints
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Laminated on every scale?
21
Figure 2 On every scale, formations may have laminations that hinder vertical permeability and fracture penetration.Shown are thin laminations in the Middle Bakken [LeFever 2005], layering in the Woodford [outcrop photo courtesy ofHalliburton], and large scale laminations in the Niobrara [outcrop and seismic images courtesy of Noble]
SPE 146376
Woodford Shale Outcrop
Some reservoirs posechallenges to effectively
breach and prop throughall laminations
Rational Expectations?
Our understanding of fracbarriers and k v should
influence everything fromlateral depth to frac fluidtype, to implementation
Narrower aperture plussignificantly higher stress inhorizontal steps?
Failure to breach all laminae?
Will I lose thisconnection due to
crushing of proppant inhorizontal step?
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Fractures Intersecting Stacked Laterals
Modified from Archie Taylor SPE ATW Aug 4 201023
23 ft thick Lower Bakken Shale
Fraced Three Forks well ~1MM lb proppant in 10 stages1 yr later drilled overlying well in Middle Bakken;
Kv
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With what certainty can we explain this production?
SPE 106151 Fig 13 Production can be matched with a variety of fracture and reservoir parameters25
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 100 200 300 400 500 600
Production Days
S t a g e
P r o
d u c
t i o n
( m c
f d )
0
20
40
60
80
100
120
140
160
180
200
C u m u
l a t i v e
P r o
d u c t
i o n
( M M s c
f )
Actual Production Data
Nice match to measured microseismic, eh?
SPE 106151 Fig 13 Production can be matched with a variety of fracture and reservoir parameters26
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 100 200 300 400 500 600
Production Days
S t a g e
P r o
d u c
t i o n
( m c
f d )
0
20
40
60
80
100
120
140
160
180
200
C u m u
l a t i v e
P r o
d u c t
i o n
( M M s c
f )
Actual production data
Long Frac, Low Conductivity500' Xf, 20 md-ft, 0.5 uD perm, 23 Acres 4:1 aspect ratio
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Is this more accurate? Tied to core perm
SPE 106151 Fig 13 Production can be matched with a variety of fracture and reservoir parameters27
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 100 200 300 400 500 600
Production Days
S t a g e
P r o
d u c
t i o n
( m c
f d )
0
20
40
60
80
100
120
140
160
180
200
C u m u
l a t i v e
P r o
d u c t
i o n
( M M s c
f )
Actual production data
Long Frac, Low Conductivity
Medium Frac, Low Conductivity
500' Xf, 20 md-ft, 0.5 uD perm, 23 Acres 4:1 aspect ratio
100' Xf, 20 md-ft, 5 uD perm, 11 Acres 4:1 aspect ratio
Can I reinforce my misconceptions?
SPE 106151 Fig 13 Production can be matched with a variety of fracture and reservoir parameters28
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 100 200 300 400 500 600
Production Days
S t a g e
P r o
d u c
t i o n
( m c
f d )
0
20
40
60
80
100
120
140
160
180
200
C u m u
l a t i v e
P r o
d u c t
i o n
( M M s c
f )
Actual production data
Long Frac, Low Conductivity
Medium Frac, Low Conductivity
Short Frac, High Conductivity, Reservoir Boundaries
500' Xf, 20 md-ft, 0.5 uD perm, 23 Acres 4:1 aspect ratio
100' Xf, 20 md-ft, 5 uD perm, 11 Acres 4:1 aspect ratio
50' Xf, 6000 md-ft, 10 uD perm, 7 Acres 4:1 aspect ratio
History matching of production issurprisingly non-unique.
Too many knobs available to tweak We can always blame it on the geology
Even if I know it is a simple planar frac, I cannotprove whether it was inadequate reservoir quality, or
inadequate completion with a single well
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1. Complex Flow Regimes 100x higher pressure losses
2. Conductivity Degrades3. Heterogeneous Reservoirs
Dependant on fracs to connect reserves
4. Complex Frac Geometry Require commensurate increase in conductivity
5. Non-unique interpretations
5 Things You Didnt Want to Know
Removing the Uncertainty If we require a production match of two different
frac designs, we remove many degrees offreedom lock in all the reservoir knobs!
Attempt to explain the production results frominitial frac AND refrac
143 published trials in SPE 134330 100 Bakken refracs 136757
Require simultaneous match of two differentfrac designs in same reservoir !
200+ trials in SPE 11914330
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Field Studies Documenting Production Impact with Increased Fracture Conductivity
>200 published studies identified,authored by >150 companies
SPE 119143 tabulates over 200 field studies
Oil wells, gas wells, lean and rich condensateCarbonate, Sandstone, Shale, and Coal
Well Rates Well Depths1 to 25,000 bopd 100 to 20,000 feet
0.25-100 MMSCFD
31
Dataset Limitations Intentional
Eliminated most field examples with dramatic fluidrheology changes
Are production gains attributed to proppant transport(frac length), differing gel cleanup, differing frac heights?
Unintentional Its just my literature review. Certainly I missed some
excellent papers
Publication Bias Industry rarely publishes failures Nonetheless I summarize 10 examples of exceptions to
the rule
A tabulation of 200 papers in SPE 11914332
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Production Benefit
In >200 published studies and hundreds ofunpublished proppant selection studies, Operators frequently report greater benefit than
expected using: Higher proppant concentrations More aggressive ramps, smaller pads Screen outs Larger diameter proppant Stronger proppant Higher quality proppant More uniformly shaped & sized proppant
Frac conductivity appears to be much moreimportant than our models or intuition predict!
A tabulation of 200 papers in SPE 11914333
We are 99.9% certain the Pinedale Anticline was constrained by proppant quality
Effect of Proppant Selection upon Production
0
100
200
300
400
500
600
700
800
900
L L 3
L L 2
L L 1
M V 5
M V 4
M V 3
M V 2
M V 1
M V 0
A v e r a
g e
Reservoir Sub-Interval (Lower Lance and Mesa Verde)
P r o
d u c t
i o n R
a t e 1 0 0 d a y s p o s
t - f r a c
( m c
f d )
Versaprop
CarboProp
ISP-BS
ISP 20/40
Averages based on 95 stages ISP-BS and 54 stages ISP 20/40
SPE 106151 and 108991
70% increasein productivityachieved with
a moreuniformly
sizedproppant!
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Can we learn from refracs?
Pagano, 2006
Gas Condensate wells in DJ Basin up to 5restimulations
Increase Conductivity in Refracs? Dozens of examples in literature
Shaefer, 2006 17 years later,tight gas
0
500
1000
1500
2000
2500
3000
3500
J an -9 0 J an -9 1 J an -9 2 J an -9 3 J an -9 4 J an -9 5 J an -9 6 J an -9 7 J an -9 8 J an -9 9 J an -0 0 J an -0 1
G a s
R a t e ,
M C F D
0
50
100
150
200
250
300
350
400
450
500
W a t e r
R a t e ,
B W P D
GasWater
Initial Fracin1989:
48,000 lb 40/70sand + 466,000lb 12/20sand
May1999Frac:
300,000lb 20/40LWC
May1995Frac:
5,000lb100 mesh+ 24,000lb 20/40
Sand
Vincent, 2002 9 years later,CBM
0
500
1000
1500
2000
2500
3000
3500
4000
M a y-84 May-86 May-88 May-90 May-92 May-94 May-96 May-98 May-00
Date
P r o
d u c t
i o n
f r o m
F r a c t u r e
( b f p d )
Original Fracture (20/40 Sand)Phase I refrac (20/40 Sand)Phase III refrac (16/20 LWC)
IncrementalOilExceeds
1,000,000barrels
IncrementalOilexceeds
650,000barrels
FirstRefrac
SecondRefrac
Pospisil, 1992 6 years later,20 mD oil
0
500
1000
1500
2000
2500
S t a b i l i z e d
R a t e
( M S C F D )
P re Fr ac 1 0, 00 0 g al3% acid +10,000 lb
glass beads
80,000 gal +100,000 lb20/40 sand
75,000 gal +120,000 lb20/40 ISP
Ennis, 1989 sequentialrefracs, tight gas
0
2 0
4 0
6 0
8 0
1 0 0
1 2 0
W e l l A W e l l B W e l l C W e l l D W e l l E
P
r
o
d
u
c
t
i o
n
R
a
t
e
(
t o
n
n
e
s
/ d
a
y
)
.
.
I n i t i a l F r a c
R e f r a c
Dedurin, 2008, Volga-Uralsoil
36
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1) Incredible reservoir contact provided by hydraulic fractures2) Bad News: Fracs are not optimized
Fluid flow is complicated Frac geometry is tortuous Connection between the frac and wellbore is tenuous Laminated reservoirs depend on vertical frac continuity Many fractures collapse or heal
3) Great News: Fracs are not optimized Reservoirs are often capable of tremendous increases in
productivity with improved frac design
Summary
Five things you didnt want to knowabout hydraulic fractures
Mike Vincent
FracwellLLC
.pdf version of [email protected]