Petroleum Geomechanics for Shale Gas - bgc.bgbgc.bg/upload_files/Lyesse Laloui.pdf · Petroleum...

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

http://www.petrosvibri.ch/


2

Unconventional Gas Shale Gas


3

Unconventional Gas Shale Gas

Shale gas may create 100,000 jobs in France. Challenges, September14th 2012


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.


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


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


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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.


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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.


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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


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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


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FACTS • High temperatures: may reach 100°C • High pressures: dozens of MPa’s

CHALLENGING IN-SITU CONDITIONS

Experimental representation in laboratory


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Los Angeles Times, April 1st 2012

Accumulation of

irreversible settlements.

Retention properties of shales

OCR=1


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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


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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)

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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


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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


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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


Test results


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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


Test results: evaluation of Shale permeability


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Experimental tools THMC


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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,…


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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,…


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

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