petroleum geomechanics for shale gas - bgc.bgbgc.bg/upload_files/lyesse laloui.pdf · petroleum...
TRANSCRIPT
Petroleum Geomechanics
for Shale Gas
Prof. Lyesse LALOUI Chair Professor « Gaz Naturel »
Ecole Polytechnique Fédérale de Lausanne, EPFL
3rd UNECE Gas Centre Industry Forum
Acknowledgement: V. Favero, A. Ferrari, L. Chao
3rd UNECE Gas Centre Industry Forum
3
Unconventional Gas Shale Gas
Shale gas may create 100,000 jobs in France. Challenges, September14th 2012
3rd UNECE Gas Centre Industry Forum
4
Unconventional Gas Reservoir Characteristics Conventional and unconventional gases differ not by their chemical compositions (all these resources are natural gas) but rather by the geological characteristics of their reservoir rock.
Permeability Challenges: Rock (matrix) permeability and porosity in unconventional reservoirs are much lower than for conventional reservoirs.
3rd UNECE Gas Centre Industry Forum
5
Low values of porosity
(between 3% and 7%) Source: “Investigating the Microstructure of Gas Shales by FIB/SEM Tomography & STEM Imaging” Mark E. Curtis, Raymond J. Ambrose, Carl H. Sondergeld, and Chandra S. Rai University of Oklahoma
Red blood cells ≈ 2-5 μm
Atoms of silicon ≈ 10 nm
Human hair ≈ 50 μm
Low values of water saturation
(between 10% and 50%)
High values of
negative water
pressure
(High Suction)
Ant ≈ 5 mm
Unconventional Gas Reservoir Characteristics
3rd UNECE Gas Centre Industry Forum
6
Unconventional Gas Reservoir Characteristics Conventional and unconventional gases differ not by their chemical compositions (all these resources are natural gas) but rather by the geological characteristics of their reservoir rock.
Permeability Challenges: Rock (matrix) permeability and porosity in unconventional reservoirs are much lower than for conventional reservoirs.
Fracturing as a solution: As a result, unconventional reservoirs only have commercial potential if the rock is fractured.
Natural and created fractures enhance flow potential but
the location and properties of underground fractures are
difficult to measure or forecast.
Total, 2012
3rd UNECE Gas Centre Industry Forum
7
Additives protect the wellbore from corrosion
and improve the effectiveness of the fracture
stimulation.
Hydraulic Fracturing
Injection of water sand and additives
under pressure.
Source: Drilling and completing shale gas wells, horizontal drilling and well construction. New Brunswick.
Strong chemical composition: chemo-
osmotic phenomena in Shales can be of
primary importance.
3rd UNECE Gas Centre Industry Forum
8
We come across new questions
How does the gas permeability evolve after fracturing during gas extraction?
The Injected pressure must be greater than the horizontal stress in Shales…
… but how greater?
State officials acknoledge that they have little information about
the scale or practice of fracking in California. Los Angeles Times, April 1st 2012
Need to test under stress and negative water
pressure (suction) control.
3rd UNECE Gas Centre Industry Forum
9
Geomechanical behaviour of shales A multiphysical research approach
Mechanics Constitutive laws, stress redistribution,
stiffness and strength variations, self sealing
capacity
Hydraulics Changes in saturation state, retention properties, capillary
effects, hysteretical behaviours, permeability dependency on
the degree of saturation,
Temperature Thermal conductivity, thermal gradients, thermal
fracturing
Chemistry Changes in pore fluid composition
Chemical weathering
3rd UNECE Gas Centre Industry Forum
10
an exhaustive characterization of the behavioural features of shales requires to deal simultaneously with four major physical aspects and their coupled interactions
THCM behaviour
Experimental testing
must be collected to
assess the material
response related to
each physical aspect
and the coupled
effects
Effective
stress
Suctio
n ch
ange
D
essicatio
n cracks
Porosity Thermal conductivity
Heat convection
Osm
oti
c e
ffic
ien
cy
Ion
dif
fusi
on
rat
e
Osmotic efficiency Porosity
Porosity Osmotic suction
H Water and gas
flow
T Heat
conduction
M Stress-strain framework
C Chemo-osmotic
processes
Heat convection Thermal conductivity
Specific heat
Fluid density Fluid viscosity
Geomechanical behaviour of shales A multiphysical research approach
3rd UNECE Gas Centre Industry Forum
11
FACTS • High temperatures: may reach 100°C • High pressures: dozens of MPa’s
CHALLENGING IN-SITU CONDITIONS
Experimental representation in laboratory
3rd UNECE Gas Centre Industry Forum
12
Los Angeles Times, April 1st 2012
Accumulation of
irreversible settlements.
Retention properties of shales
OCR=1
3rd UNECE Gas Centre Industry Forum
13
T= 80°C
T= 21°C
The water retention capability of the soil is reduced by an increase in temperature
T= 80°C
T= 21°C
T= 80 C
T= 21 C
AEV80 C≈1MPa
4MPa
A faster decrease of the void ratio can be observed with the higher temperature.
A decrease of the air-entry-value with suction is observed
Opalinus Clay Retention Properties at Different Temperatures - EPFL
Retention properties of shales
3rd UNECE Gas Centre Industry Forum
14
High pressure Oedometer testing
Main features
Max. vertical stress 100 MPa
Independent control of pwp at the two bases (0 – 2 MPa)
Available layouts for temperature control (4 – 120°C) and suction control (4 – 400 MPa)
3
Vertical stress (log)
Vo
id r
atio
4
1
2
2
2
1. Saturation at constant volume
(synthetic water)
2. Loading/unloading cycles
3. Assessment of the initial yield
stress
4. Assessment of the NCL
3rd UNECE Gas Centre Industry Forum
15
High pressure oedometric tests on Shales
Test results: evaluation of the compressibility
The mechanisms of subsidence
Most of the deformation takes place in the reservoir layers
Source: US geological survey
3rd UNECE Gas Centre Industry Forum
16
0,1
0,11
0,12
0,13
0,14
0,15
0,16
0,17
0,18
0,001 0,01 0,1 1 10 100
s = 15 MPas = 20.2 MPa
Void
ratio
[-]
Total stress [MPa]
Ambient temperature
Suction effects
0,04
0,06
0,08
0,1
0,12
0,14
0,16
0,18
0,1 1 10 100
T° = 22°CT° = 80°C
Void
ratio
[-]
Total stress [MPa]
Suction = 4 MPa
Temperature effects
High pressure oedometric tests on Shales
Test results
3rd UNECE Gas Centre Industry Forum
17
Source: “Investigating the Microstructure of Gas Shales by FIB/SEM Tomography & STEM Imaging” Mark E. Curtis, Raymond J. Ambrose, Carl H. Sondergeld, and Chandra S. Rai University of Oklahoma
Good estimation of the coefficient of permeability can be achieved.
v w
oed
cK
E
High pressure oedometric tests on Shales
Test results: evaluation of Shale permeability
3rd UNECE Gas Centre Industry Forum
19
Appraisal Initial stress estimation,
Pore pressure prediction,…
Approach Horizontal drilling,
Wellbore stability..
Harvest Subsidence,
Induced Seismicity,…
Geomechanics Through the Life of a Reservoir
Development Injected pressure,
Fracture Stimulation,…
3rd UNECE Gas Centre Industry Forum
20
Reservoir Material Behaviour involved in engineering issues Several areas of the Oil & Gas industries involve Thermo-Hydro-Mechanical – Chemo (THMC) problems related to reservoir geo-materials.
Appraisal Initial stress estimation,
Pore pressure prediction,…
Stress redistribution, Thermal impact,
Chemical effect,…
Saturation/Desaturation, Capillary forces,
Self-sealing capacity,…
THMC Behaviour of Geo-Materials
Development Injected pressure,
Fracture Stimulation,…
Approach Horizontal drilling,
Wellbore stability..
Harvest Subsidence,
Induced Seismicity,…
3rd UNECE Gas Centre Industry Forum
21 First fracture stimulation from 1949 in Grant County, Kansas
• A comprehensive analysis of shale behaviour requires different physical aspects and the coupled effects to
be investigated
• Collecting proper experimental evidence for shales
requires specific apparatuses and techniques
• Collected experimental results are used for the
development of a comprehensive THM(C)
constitutive modelling framework
Advances in Testing the Hydro-Mechanical Behaviour of Shales