P and s wave velocities in rock as a function of pressure and temperature
1 / 38

P- and S-wave velocities in rock as a function of pressure and temperature - PowerPoint PPT Presentation

  • Uploaded on

P- and S-wave velocities in rock as a function of pressure and temperature. I. Lassila 1 ,T. Elbra 2 , E. H æggström 1 and L. J. Pesonen 2 V. Kananen 1 and M. Perä J. Haapalainen 1 and R. Lehtiniemi 3 P. Heikkinen 4 and I. Kukkonen 5. 1 Electronics Research Unit

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' P- and S-wave velocities in rock as a function of pressure and temperature' - loring

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
P and s wave velocities in rock as a function of pressure and temperature

P- and S-wave velocities in rock as a function of pressure and temperature

I. Lassila 1,T. Elbra 2, E. Hæggström1 and L. J. Pesonen 2

V. Kananen1 and M. Perä

J. Haapalainen1 and R. Lehtiniemi 3

P. Heikkinen 4 and I. Kukkonen 5

1 Electronics Research Unit

2 Division of Geophysics

3 Nokia Research Center

4 Institute of Seismology

5 Geological Survey of Finland

Motivation understanding the structure of the earth s crust
Motivation - Understanding the structure of the earth’s crust

  • FIRE (Finnish Reflection Experiment) - project

  • Seismic reflection and refraction measurements (longitudinal and shear wave modes)

Photo: Seismic signal is produced by vibrators. Courtesy Jukka Yliniemi.

Location of the FIRE reflection seismic lines.

Tof and depth
TOF and depth crust

  • Seismic measurements give TOF data

  • Need to know Vp and Vs to calibrate the depth

Example of FIRE results from the end of line FIRE 3A in western Finland. The reflector amplitudes of a migrated section are presented as gray tone intensities.

Samples crust

  • Outokumpu Deep Drilling Project (2516 m)

Device requirements
Device: requirements crust

  • Vp and Vs measurements

    • preferably simultanously

    • 10 m/s accuracy

  • Controlled pressure

    • 0 - 300 MPa (15 ton for OKU samples)

  • Controlled temperature

    • 20-300ºC

  • Data acquisition

    • Preferably automatic

22 mm

25 mm

Possible measurement setups
Possible measurement setups crust

  • Uniaxial

  • Multianvil

  • Hydrostatic pressure

Timetable crust

Jan Feb Mar Apr May Jun Jul

Material considerations

Mechanical design

Ultrasonic testing and designing

Transducers, pulser / signal generator, amplifiers, switches, oscilloscope

Pressure generating

Pressure monitoring


Temperature monitoring

Transducer cooling

Ordering parts

Planning the measurement procedure

Assembling the setup

Programming the DAQ software


Device vp and vs
Device: Vp and Vs crust

  • Pitch-catch method

  • Two similar transducers, both comprising shear (1,1 MHz) and longitudinal (1 MHz) piezo (Pz-27) ceramics

  • At first only the shear crystal was in use

    • Longitudinal mode well present

    • Caused by silver epoxy?

  • Removable delay lines

    • Fused quartz

    • Brass

  • Water cooling

  • No load over the piezo crystal

Device pressure simulation
Device: pressure simulation crust

  • Pressure simulations by Mr. Haapalainen

    • Device can withstand the required pressure

    • Fused quartz can be used as a delay line material in case of no roughness

Device pressure
Device: pressure crust

  • Generating: 15 ton jack borrowed from Department of Chemistry

  • Measuring: Sensotec Model 53 (max 23 ton) + Lebow 7528 amplifier

Device pressure1
Device: pressure crust

  • Problem with sample durability

  • Solved with a brass jacket

  • Splitting sample holder allows sample removal after compression

Device temperature simulations
Device: Temperature, simulations crust

  • Thermal simulations by PhD Lehtiniemi and Mr. Haapalainen

    • 160 W heater is sufficient for 300ºC in case of fused quartz delay lines

    • Transducer temperature stays below solder melting / epoxy softening temperature

Device temperature
Device: Temperature crust

  • Heating: Nozzle heater ACIM T197 (160 W / 240 Vac)

    • Max 400ºC

    • Covers the sample holder

  • Cooling: Water cooler (Lauda WK502)

  • Measuring: Custom AD595 based thermocouple amplifier

    • K-type Thermocouple inside the sample holder

Device data acquisition
Device: Data acquisition crust

  • US signals:

    • 5072 PR, LeCroy 9410, GPIB, PC, LabVIEW, Matlab

  • Thermocouple and load cell:

    • AD-conversion and transfer to PC with NI PCI-6024E

Device crust

  • Transducers

  • Delay lines

  • Heating element and sample

  • Thermocouple

  • Load cell

  • Water cooling tubes

  • Jack

Preliminary results
Preliminary results crust

  • 7 samples from Outokumpu Deep Drill Core

  • T: 300ºC20ºC, Load: 7000 kg  500 kg (resembling the conditions in the Earth’s crust)

  • Results comparable with literature values

Pressure test
Pressure test crust

  • The error if we don’t measure the compression of the sample?

  • Compression = 0,1 mm (Δhsample- Δhno sample)

  • Error Vp = 24-33 m/s

  • Error Vs = 15-18 m/s

Tof time of flight through the delay lines
TOF (time of flight) through the delay lines crust

  • Pulse-echo measurement of the delay line

  • Subtraction of the TOF through the delay lines from the total TOF

  • Pressure and temperature effects to the delay lines and transducers are cancelled

Damping the transducers
Damping the transducers crust

  • Ringing of the piezo element makes pulse-echo (PE) measurements difficult.

  • Ringing can be reduced with applying attenuating, material with acoustic impedance close to the piezo to the back side of the transducer

  • PE responses to water load

    • a) zero backing, b) backing of crown glass, c) backing of tungsten-epoxy, d) backing of material with Z=Ztransducer

Egypt. J. Sol., Vol. (23), No. (2), (2000)

Damping test ok
Damping test - ok crust

  • Reduced ringing time and increased bandwidth

Outcome of applying the backing
Outcome of applying the backing crust

  • No signal

  • Resistance between transducer electrodes ca. 5 Ω

     Short-circuit

  • Difference between test

    • Amount of tungsten in the mixture was higher

      • In the test the resistance between the electrodes was ca. 500 Ω

  • This type of backing method requires isolation of the electrodes

  • Instead of scraping out the backing it was decided to build new transducers

New transducers
New transducers crust

  • Increased sample size:

    • Height 20-70 mm

    • Diameter 25-62 mm

  • Better modal purity required

    • Mode conversion in the gap between transducer housing and delay line

    • Material: stainless steel

    • No separate delay lines

New thermal simulations
New thermal simulations crust

  • Stainless steel:

    thermal conductivity=20 W/(m K)

    Specific heat=500J/(kg K)

  • Sample (rock):

    thermal conductivity=2 W/(m K)

    Specific heat=790J/(kg K)



h = 20-70mm


D = 25-62 mm

Sample D = 25,5 mm, h = 24 mm

Sample D = 62 mm, h = 70 mm

Sample D = 25,5 mm, h = 24 mm

t = 200s.

Sample D = 62 mm, h = 70 mm,

t = 400s.

Other updates
Other updates transducer

  • PC controlled pressure generation

  • Separate heating of samples to increase the throughput rate

New frame
New frame transducer

  • Compressed air controlled one way hydraulic cylinder replaced with electric motor controlled two way hydraulic cylinder

Modification for hydraulic control
Modification for hydraulic control transducer

  • Controls of the pump replaced with relay circuit that is controlled from PC DAQ-card

  • Two valves that are controlled

    • Valve 1 open increasing pressure

    • Valve 2 open decreasing pressure

    • Valves closed no change

Testing new hydraulics
Testing new hydraulics transducer

  • Pressure increase at 0,1 s intervals

  • OK for loads over 3000 kg

Testing of new hydraulics
Testing of new hydraulics transducer

  • Pressure decrease at 0,1 s intervals

  • No control of outcome when decreasing pressure

More control needed
More control needed transducer

  • Manual shut off valve, needle type control

  • Slows down the flow of the hydraulic oil

Control achieved
Control achieved transducer

  • Needle valve can be adjusted to allow precise control of the load

Conclusions transducer

  • Device is used for measuring Vp and Vs values that are needed to interpret seismic data

  • Preliminary results ok

  • At the moment system is going through some changes

Future tasks
Future tasks transducer

  • Temperature inside the sample vs. on the sample surface

  • Validation tests

  • Implement a LVDT/gauge to measure the sample thickness and thickness change inline

  • Licentiate thesis