SHALE
ROUTINE & SPECIAL CORE ANALYSIS
Banff, Alberta Canada
9-19/21-2007
Pittsburgh, Pennsylvania
10-11/12-2008
Denver, Colorado
10-19-2009
Laboratory Analysis For Shale Gas
Characterization
SPE Applied Technology Workshop
Shale Gas Core Analysis
SPE Shale Gas Project Workshop
Vapor Desorption Capillary Pressure
DWLS Capillary Pressure Workshop
Patrick M. Lasswell
Weatherford Laboratories
Shale Basic Core Analyses Disciplines
• Total Gas Content on Recovered Fresh State Core
• Total Organic Content
• Characterization of Organic Material
• Routine Core Analyses
• Special Core Analyses
• Petrographic Analyses (FIB, SEM, XRD, T/S)
• Mechanical Properties
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2
Shale Routine Core Analysis
• Bulk and Grain Densities
• As-Received Fluid Saturations
• Free Gas Volumes: As-Received and Total
• Permeability of Intact & Preserved Matrix
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3
Routine Core Analyses
Historical Conventional Methodologies
Rotary Plugs, Plugs from Whole Core and Whole Core
Grain density and porosity determinations
Pore fluid saturations
Steady state or unsteady state gas permeabilities on dry and
as-received core materials
• Suited for conventional resources where matrix porosity is 3% or greater
• Suited for conventional resources where matrix gas permeabilities range
from 0.0001 md to 10,000 md
• TGS materials are a challenge but are usually well suited to the method
• Rarely suited for most shale plays due to size of pore throat systems
and matrix alteration during recovery
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4
Shale Gas GRI Based
(Routine) Core Analyses
Crushed Shale Investigations pioneered by Don Luffel
et al. within research sponsored by the Gas Research Institute (GRI)
• Porosity Determinations: D.L. Luffel and F.K. Guidry “New Core Analysis
Methods for Measuring Reservoir Rock Properties of Devonian Shale” SPE
20571 November 1992
• Pore Fluid Saturations: D.L. Luffel, F.K. Guidry and J.B. Curtis “Evaluation of
Devonian Shale With New Core and Log Analysis Methods” SPE 21297
November 1992
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5
Shale Gas GRI Porosity Determinations
Plug based porosities and grain densities are often much too low using
standard measurements based on Boyle’s Law helium gas expansion.
• Direct shale comparisons were conducted by Luffel on core material
designated CSW 4A. Plug based porosities averaged 2.47% and crushed
porosities averaged 7.88%. Stress based porosity reductions only account
for approximately a 1 PU shift.
• Luffel’s findings with core material CSW 2 were much less dramatic: 0.1 PU
reduction.
• Through personal observation, the porosity reduction within plug based
analysis usually fall within the 2 to 3 PU range … especially with lower
quality materials. Increased gas injection pressure did not significantly alter
these results.
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6
Crushed Shale Rock Properties
Modified GRI Method
SHALE ROCK PROPERTIES
SUMMARY OF ROUTINE CRUSHED CORE ANALYSES RESULTS
As-Received and Vacuum Dried at 105°C
Sample
ID
Depth,
feet
SRP 1
SRP 2
SRP 3
SRP 4
SRP 5
SRP 6
SRP 7
SRP 8
SRP 9
SRP 10
SRP 11
SRP 12
SRP 13
SRP 14
Average
values:
A-R
Bulk
Density,
gm/cc
A-R
Grain
Density,
gms/cc
A-R
A-R
A-R
Water
Oil
Gas
Saturation, Saturation, Saturation,
% of PV
% of PV
% of PV
2.63
2.60
2.69
2.51
2.43
2.57
2.49
2.30
2.26
2.33
2.38
2.30
2.64
2.70
2.75
2.73
2.72
2.69
2.63
2.66
2.66
2.50
2.43
2.53
2.52
2.48
2.69
2.74
30.2
27.5
65.8
24.2
20.4
33.4
27.5
20.9
20.3
16.5
23.1
17.7
23.5
30.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.9
1.0
0.9
1.3
0.0
0.3
2.49
2.62
27.2
0.3
A-R
Gas Filled
Porosity,
% of BV
A-R
Press Decay
Permeability,
md
Dry
Bulk
Density,
gm/cc
Dry
Grain
Density,
gm/cc
Dry
Helium
Porosity,
% of BV
69.8
72.5
34.2
75.8
79.6
66.6
72.5
79.1
78.9
82.5
76.0
81.0
76.5
69.3
4.1
4.7
1.3
6.7
7.8
3.5
6.4
8.0
6.9
8.0
5.7
7.5
1.7
1.6
4.07E-05
3.61E-05
1.23E-05
3.92E-04
6.19E-04
8.74E-05
3.77E-04
8.86E-04
1.74E-04
9.22E-04
8.69E-05
2.17E-04
2.84E-05
1.38E-05
2.61
2.58
2.66
2.48
2.41
2.55
2.47
2.28
2.25
2.31
2.36
2.28
2.64
2.69
2.78
2.76
2.77
2.73
2.67
2.69
2.70
2.54
2.46
2.56
2.55
2.51
2.70
2.75
5.9
6.5
3.8
8.9
9.8
5.2
8.8
10.1
8.8
9.6
7.4
9.3
2.2
2.3
72.5
5.3
2.78E-04
2.47
2.65
7.0
As-received bulk volumes and bulk densities were determined on intact bulk sample material. The bulk material was crushed and all other analysis reported herein were conducted on the crushed material.
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7
Crushed Shale Rock Properties
GRI Density, Saturation & Porosity Determinations
Wellsite and Rock Shop
• Retention of as-received fluid saturations through minimal and controlled
exposure of core material.
• Insulated core transport. Chilled whole core storage under humidified
positive vapor pressure conditions.
• Retention of as-received fluid saturations through sample preservation via
immediate Saran & foil wrapping with / or without additional wax dip steps.
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8
Shale Sample Allocation
• Inter-related data patterns can be difficult to interpret if
sampling is not approached carefully
• Cross discipline data sets must remain linked (Petrology,
Geochemistry, Basic Sample Properties)
• Shale bedding / properties variable on an inch scale
• Therefore, all sampling should be from the same bedding
planes for all analyses at a given depth
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9
Crushed Shale Rock Properties
GRI Density, Saturation & Porosity Determinations
As-Received State Sample Handling in the Laboratory:
Bulk Volume and Sample Crushing
• Recommend processing one sample at a time during the As-Received state
where a sample is most vulnerable.
• Bulk whole core cross section is trimmed to remove any mud contaminated
rind. Recommend 200 to 300 grams of bulk As-Received material
• Rotary samples should have exterior mud contamination removed by
physically wiping the sample exterior. Subject to fluid saturation shifts.
While a maximum weight of material is ideal, a minimum of 40 grams
combined weight with rotary samples is recommended. Small rotary
samples should be combined to achieve a 40 gram minimum per
composite.
• Weigh sample. Determine bulk volume using immersion. This is usually
done using mercury. If the Archimedes methodology is used, imbibition
must be accounted for. Re-weigh sample as applicable. With cuttings, bulk
volume determination can be done using a Micromeritics mercury intrusion
apparatus.
• Single pass mechanical crushing to yield approximately 1/8” and less
particle size. GRI calls for sieving of the material (20-35 mesh) but
saturation change has been observed during this added handling step.
• Immediately weigh and secure the sample. Minimize exposure.
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10
Crushed Shale Rock Properties
Modified GRI: As-Received Gas in Place Determination
As-Received State Sample Handling in the Laboratory:
AR Grain Volume
• This step is not part of the original GRI methodology. It is recommend as it
provides an additional material balance step to check fluid saturations.
• Directly transfer the sample to the lab following the crushing process. (If A-R
permeabilities are part of the test program, split out and retain an appropriate
sample aliquot. If only minimal material is available, conduct the A-R
permeability measurement first.)
• Weigh. Measure As-Received grain volume using Boyle’s Law helium
expansion. Repeat. Re-weigh.
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11
Crushed Shale Rock Properties
GRI and Modified GRI: As-Received Fluid Saturation Determinations
• The GRI process used the standard Dean-Stark toluene extraction process
to determine fluid saturations.
A. Removes free and bound water.
B. Removes the bulk of the free oil as well as bitumin. It does not remove pyrobitumin
or kerogen.
C. It may not efficiently remove all of the heavy oil compounds from the pore structure.
• A ramped temperature retort process is also being used as an alternative
method for fluid saturation assessment. Here, free and bound water and oil
fractions are captured and reported.
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12
Crushed Shale Rock Properties
GRI Saturation Determinations
As-Received State Sample Extraction:
Dean-Stark Toluene Extraction of Pore Fluids
• It is recommended that each sample is transferred into a tare for
the duration of the extraction and drying processes. This minimizes
sample loss which would be otherwise attributed to an oil volume.
• Removes free water, bound water and oil.
• Total water is separated and recovered.
• Timing (3-7 days) dependant upon verified stabilization of the water
volume.
• The recovered water is weighed and recorded.
• It is recommended that oil bearing shale should be further
extracted with chloroform/methanol azeotrope to insure that pore
throats are unobstructed.
• Vent samples to allow for the removal of excess toluene or
chloroform/methanol azeotrope.
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13
Crushed Shale Rock Properties
GRI Density, Saturation and Porosity Determinations
Dry State Sample Handling in the Laboratory: Dry Grain Volume and
Total Porosity Determinations
• Following solvent venting, the sample (and tare) is placed into a vacuum oven at
105C.
• Care to minimize the absorption of water from the atmosphere must be taken.
Samples are vulnerable to grain volume and porosity errors.
• The weight of each sample is monitored to stability. Typically this takes 3-5 days. It
is recommended that each sample (and tare) cools in an isolated container with
desiccant so that no water absorption is allowed prior to each weight recording.
• The weight difference between the As-Received state and the dry state is used to
determine the combined oil and water volumes. The weight differential must be
carefully protected.
• Weigh. Determine dry grain volume using Boyle’s Law helium expansion. Repeat.
Re-weigh sample.
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14
Crushed Shale Rock Properties
Modified GRI Porosity Determinations
Effective Porosity Determinations
• If the ramped temperature retort process is used to determine the fluid saturations,
then typically, a total dry porosity model is not being used.
• Instead, an effective porosity is reported.
• Note: If Dean-Stark toluene extraction is used to determine the fluid saturations,
then a separate As-Received sample aliquot must be processed if the water
content is to be separated into free and bound fractions. Unless this is done, then
only a total porosity can be reported.
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15
As Received and Dry Weight Stability
Sample Handling and Process Control Are Critical
As Received Shale Subject to Evaporation of Pore Fluids
As Received State Weight Loss per Time, minutes
Water Loss, %
5
10
15
30
60
0.030
0.060
0.080
0.170
0.180
-10.0
0.060
0.100
0.100
0.140
0.180
-10.0
0.070
0.110
0.130
0.190
0.230
-19.0
Dried Shale Subject to Water Sorption from the Atmosphere
Dried State Weight Gain per Time, minutes
Water Gain, %
5
10
15
30
60
0.170
0.320
0.370
0.430
0.460
+25.6
0.300
0.370
0.400
0.470
0.480
+26.7
0.170
0.220
0.260
0.320
0.330
+18.3
• Weight change based on 120 gram samples
• Examples are from a gas shale where an estimate of volumetric change can be
made with the assumption that 1 cc water = 1 gram water
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16
Review of GRI Material Balance and QC Steps
• Multiple Discipline Sampling Taken Over the Same Depth Range
with the Same Bedding Strata Represented.
• Minimize sample exposure during critical test stages.
• Recommend repeating all volumetric determinations.
• Recommend taking sample weights before and after each handling
step.
• With Dean-Stark extraction, it is recommend recording the
discoloration of the extraction solvents to provide a comparative
assessment of oil content within a given sample set.
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17
Shale Gas Permeability Determinations
•
Brief Methods Overview
•
Crushed Permeability Examples and Variables
•
Crushed Permeability Lab Data Comparisons
•
SS Permeability Measurements
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18
Shale Permeability Models Brief Review
1.
J.Kamath, Characterization of Core Shale Heterogeneities…
Pressure Transients (1992)
2.
X.Ning, Matrix and Fracture Properties (1993)
3.
Crushed Models by Luffel (1993)
4.
Egermann (IFP) Darcylog using Oil Injection (2002)
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19
Shale Gas GRI Matrix Permeability Determinations
Gas Permeability Determinations: D.L. Luffel, C.W. Hopkins and P.D. Schettler
“Matrix Permeability Measurement of Gas Productive Shales” SPE 26633 Oct.1993
Plug based permeability determinations are often magnitudes too high using standard
measurements as the shale matrix is often fractured and altered during recovery.
Luffel et al compared and contrasted permeability methodologies used in shale
investigations. They developed a pressure decay based permeability determination
method for crushed as-received matrix material as well as a pressure rebound method
for shale plugs.
Direct permeability comparisons were conducted by Luffel on various core materials
as well as low permeability vycor glass using their two methodologies. Results while
not exact, were comparable.
In a broad industry comparison of matrix based permeability response, laboratory
permeabilities while repeatable and independently cross-checked do not necessarily
match field tests and historic performance.
Laboratory permeabilities should therefore be considered as comparative inter formation values. A part … in the whole of gas resource delivery.
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20
As Received GRI Based
Crushed Permeability Measurements
1. Typical Pressure / Time Response
2. Fraction Size
3. Sample Variation
4. Handling Artifacts
5. Sieving Effects
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21
As Received Crushed Shale
Pressure Decay Permeability
• As Received State
• 1x10-3 md and below
• Initial Pressure: app.99 psi
• Final Pressure: app. 94 psi
• Run Time: 30 to 60 min
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1.47 * 10 -5 md
• Sample Weight: App. 85 g
1.50 * 10 -5 md
• Particle Size: < 1/8”
22
Laboratory Comparisons
Permeability and AR % GIP Measurements
1. Data Set 1
2. Data Set 2
3. Data Set 1 and 2 Composite
4. Data Set 2 Permeability Methods Composite
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23
Permeability vs. AR Gas In Place
Data Set 1
1.00E-02
AR OMNI
Lab B
1.00E-03
Crushed Gas Permeability, md
Lab A
1.00E-04
1.00E-05
1.00E-06
1.00E-07
1.00E-08
0.0
2.0
4.0
6.0
8.0
10.0
12.0
As Received Gas in Place, % Vb
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24
Permeability vs. AR Gas In Place
Data Set 2
1.00E-03
Crushed Gas Permeability, md
1.00E-04
1.00E-05
Lab C Crushed USS
OMNI AR Crushed USS
1.00E-06
1.00E-07
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Gas in Place and As Received Gas in Place, %Vb
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25
Permeability vs. AR Gas In Place
Composite Data Sets 1 and 2
1.00E-02
Crushed Gas Permeability,md
1.00E-03
1.00E-04
1.00E-05
Set 2 Lab C Crushed
Set 1 AR Crushed
1.00E-06
Set 1 Lab A Crushed
Set 2 AR Crushed
1.00E-07
1.00E-08
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
Crushed AR Gas in Place, % Vb
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26
SS vs. USS Crushed Shale Permeability
Data Set 2
1.00E-03
Crushed Gas Permeability, md
1.00E-04
1.00E-05
Lab C Crushed USS
OMNI AR SS disc
OMNI AR Crushed USS
1.00E-06
1.00E-07
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Gas in Place and As Received Gas in Place, %Vb
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27
Steady-State
As-Received Permeability Measurements
1. Plug Analysis
2. Disc Analysis
3. Klinkenberg Verifications
4. Low Permeability Response vs. Time
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28
Steady State Effective Permeabilities
Epoxy Filled Fractures vs Open / Partial Fractures
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29
As-Received Shale Steady-State
Gas Permeability Determinations
Permeability to Air, md
Shale Disk SS Gas Permeability
0.00014
y = 8E-05x + 5E-05
0.00012
•
Multi Point Steady State Gas
Permeabilities
•
Disk and Plug Measurements
•
Verify Permeability vs. Mean
Pressure Response using
Klinkenberg Method
0.00010
0.00008
0.00006
0.00004
0.00002
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1/Mean Pressure, atm
Shale Plug SS Gas Permeability
Permeability to Air, md
0.000050
0.000040
0.000030
0.000020
y = 6E-05x + 3E-06
0.000010
0.000000
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1/Mean Pressure, atm
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30
Steady-State Gas Permeability Stability
AR Disk SS Gas Permeability
0.000016
Ka, md
0.000014
0.000012
0.00001
0.000008
0.000006
0.000004
0
50
100
150
200
250
300
Throughput Volum e, Vp
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31
SS vs. USS Crushed Shale Gas Permeability
SS and Crushed Dry Permeability to Air, millidarcys
1
0.1
0.01
Set 1 SRP
0.001
Set 1 Routine SS
Set 2 SRP
Set 2 Routine SS
Set 3 SRP
0.0001
Set 3 Routine SS
Set 4 SRP
Set 4 Routine SS
1E-05
0
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2
4
6
8
Dry Gas In Place, percent Vb
10
12
32
Shale Oil Plays – Permeability Considerations
• AR Crushed Gas Permeability at Sw and So
• Dry Crushed Gas Permeability Post Cleaning
• AR Steady State Effective Oil Permeability
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33
Steady-State AR Oil Permeability Test Cells
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34
Steady-State AR Oil Permeability Stability
Effective Oil Permeability, md
1.00E-02
1.00E-03
1.00E-04
1.00E-05
0.
100.
200.
300.
400.
500.
600.
Elapsed Time, hours
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35
SS KoSwi vs. USS Crushed Dry Permeability
0.1
Steady State Effective KoSwi
Crushed Dry Gas Permeability
Permeability, md
0.01
0.001
0.0001
0.00001
1
2
3
4
5
Sample
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36
Shale Oil Plays – Supportive Analysis
• ROQ: (Volatile, Distillable and Crackable Oil
• S1 and S2 Geochemical Analysis
• Capture of Solvent Extracts (Dean-Stark) and
Chromatography
• Asphaltene Content
• Alterative Fischer Assay capturing Water and Oil
components
• Thermal Maturity
• HgPc / (Vapor Desorption) Characterization of Pore
Geometry
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37
Shale Special Core Analyses
•
Limited Flow and Fluid Studies
•
Kg vs Sw Response in Gas Plays
•
Mercury Injection Capillary Pressure
•
A/B Vapor Desorption Capillary Pressure
•
Methane Studies
•
NMR
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38
Shale Gas KgSwi Vs Percent Gas in Place
Individual Sample Trends
Crushed As Received Permeability to Air, millidarcys
0.001
0.0001
0.00001
0.000001
0.0000001
0
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1
2
3
4
As Received Gas In Place, percent Vb
5
6
39
A/B Vapor Desorption Capillary Pressure
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40
A/B Vapor Desorption Capillary Pressure
Pore
A/B psi
Throat
RH,
Degrees,
Pc,
radius
diameter
radius
diameter
fractional
C
psig
microns
microns
nm
nm
0.99
30.0
211
0.0913
0.183
91.3
182.5
0.98
30.0
424
0.0469
0.0939
46.9
93.9
0.96
30.0
856
0.0236
0.0473
23.6
47.3
0.94
30.0
1298
0.0157
0.0314
15.7
31.4
0.92
30.0
1749
0.0117
0.0233
11.7
23.3
0.90
30.0
2210
0.0093
0.0185
9.25
18.5
0.80
30.0
4681
0.0044
0.0088
4.38
8.77
0.70
30.0
7482
0.0027
0.0055
2.75
5.49
0.60
30.0
10715
0.0019
0.0038
1.92
3.84
0.50
30.0
14540
0.0014
0.0028
1.41
2.83
0.45
30.0
16750
0.0012
0.0025
1.23
2.46
0.40
30.0
19220
0.0011
0.0021
1.07
2.14
0.30
30.0
25255
0.00081
0.0016
0.81
1.63
0.20
30.0
33760
0.00061
0.0012
0.61
1.22
0.10
30.0
48300
0.00043
0.00085
0.43
0.85
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41
TGS and Shale Vapor Desorption Data
12000
TGS FRIPc VD
TGS 2 VD Plate Pc
10000
TGS 9 VD Plate Pc
Gas-Water Capillary Pressure, psia
.
AR Shale VD
AR Shale VD
8000
AR Shale 49 VD
AR Shale 49 VD at NCS
6000
4000
2000
0
0.00
0.20
0.40
0.60
0.80
1.00
Wetting Phase Saturation , fraction pore space
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42
As-Received Crushed Shale
Vapor Desorption Data - Total Porosity
12000
Capillary Pressure, psi
10000
8000
6000
4000
2000
0
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
Fractional Saturation (Total Porosity)
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43
As-Received Crushed Shale
Vapor Desorption Data - Effective Porosity
12000
Capillary Pressure, psi
10000
8000
6000
4000
2000
0
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
Fractional Saturation - Effective Porosity
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44