Rock-physical properties of a fault zonein a porous-fractured carbonate reservoir:

Micro-geophysical in-situ and laboratory studies of a fault in the LSBB.

P.Jeanne * ,** and *** and Y.Guglielmi **

iDUST – LSBB - 2010

*** ***

• Currently, the fault zone properties are studied:

– (i) at the laboratory scale on centimeter samples

– (ii) at the reservoir scale through seismic imaging methods.

Context of the Research:

• Fault zone modern properties mainly result from:

– (1) Sedimentary rock type properties

– (2) Multi-Phase diagenetic history of the rock

Lack of decameter scale studies

that consider both matrix and fracture deformations

Coupling between (1) and (2) fault moderm properties

Geological context:•Strike-slip N20 fault

• Length = 500m

• Thickness =30m

S

Bedding planes

Fault/fractures

Burial HistoryS N

In Situ and Laboratory Micro-geophysical and

Geo-mechanical investigation methods

0

20m

50mP1 P5 P2

Gallery wall:• Geology (fracturation, sedimentary facies)

• Acoustic Velocity (Vp)

• Uniaxial Compressive Strength (UCS)

• Thin sections

Borehole logging :• Geology (fracturtion, sedimentary facies)

• Vp

• UCS

• Clay content

• Resistivity

• Density

• Water content

15m

2 m

0.14m

Acoustic sounding UCS

Thin section

Borehole logging

Micro-geophysical and

Geo-mechanical investigation methods

0.1 to 1 m

0.0001m

Water content

• Macroscopic Characterization of the Fault Damage Zone

• Acoustic Velocities Variations (VP)

• Rock Initial Porosity Alteration

• Statistical Multivariate Analysis

– Discrimination of initial sedimentary factors and fault diagenetic factors

Characterization of fractures (Gallery wall)

%

Fracturation degree (RQD)

Joint roughness

(JRC)

Joint filling

(Ja)

Joint set

(Jn)

PM

PM

PM

PMempty Clay filling empty

Rock Quality imaging around the fault zone :Fracturation is different depending on the rock type

(Barton, 2002)

Q=RQD

Jn Ja

JRC Jw

SRFx x

Variation of Q along the outcrop

Rock type

Sedimentaryfacies influence

Fault influence

• Macroscopic Characterization of the FaultDamage Zone

• Acoustic Velocities Variations (VP)

• Rock Initial Porosity Alteration

• Statistical Multivariate Analysis

– Discrimination of initial sedimentary factors and faultdiagenetic factors

Acoustic P-Waves Velocities Variations:• Strong stratigraphic contrast• Fault effect depends on rock typeV

Pvari

ati

on

s r

ela

ted

to R

ock T

yp

e

VP variations related to the fault

50m

P1 P5 P2

15m

20m

Rock Type

Sedimentaryfacies influence

Fault influence

m.s-1

m

0

2

4

6

8

10

12

14

16

18

20

0 2,5 5 7,5

km.s-1

km.s-1

0

2

4

6

15 25 35 45

• Macroscopic Characterization of the Fault Damage Zone

• Acoustic Velocities Variations (VP)

• Rock Initial Porosity Alteration

• Statistical Multivariate Analysis

– Discrimination of initial sedimentary factors and fault diagenetic factors

0.1mm 0.1mm 0.1mm

Initial Porosity alteration by the fault• Closing of Intra-Granular Porosity (blue)• Opening Peri-Granular porosity (red)

0

2

4

6

8

10

12

14

15 20 25 30 35 40 45 50

intra-granular porosity

péri-granular porosity

%

m

• Macroscopic Characterization of the Fault Damage Zone

• Acoustic Velocities Variations (VP)

• Rock Initial Porosity Alteration

• Statistical Multivariate Analysis

– Discrimination of initial sedimentary factors and fault diagenetic factors

JOINTS• RQD

• ROUGHNESS

• FILLING

• TYPE : (1) bedding planes, (2) fractures, (3) faults

• Rock Type : (1) mudstone, (2) wackstone, (3) Packstone, (4) Grainstone

Attributes Considered in the Principal Component Analysis

LOCALISATION• DISTANCE TO THE FAULT

ROCK PHYSICS• Vp (p-Wave velocity)

• UCS (Uniaxial Compressive Strength)

• JCS (Joint Compressive Strength)

• Resistivity

• Clay content

• Water content

• Density

Matrix and pore’s content ?

Axis 1: 47%

Fault influence

Axis 2: 20%

Sedimentary facies influence

CONCLUSION

FACIES A

FACIES A

FACIES B

Fault induced Macro-deformation

Fault induced Micro-deformation