Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 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. 7.12.2007 Ilkka Lassila Location of the FIRE reflection seismic lines. TOF and depth 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. 7.12.2007 Ilkka Lassila Samples Outokumpu Deep Drilling Project (2516 m) 7.12.2007 Ilkka Lassila Device: requirements Vp and Vs measurements preferably 10 simultanously m/s accuracy Controlled pressure 0 - 300 MPa (15 ton for OKU samples) Controlled temperature 20-300ºC Preferably automatic 22 mm Data acquisition 25 mm 7.12.2007 Ilkka Lassila Possible measurement setups Uniaxial Multianvil Hydrostatic pressure 7.12.2007 Ilkka Lassila Timetable Jan Feb Mar Apr May Jun Jul Material considerations Mechanical design Ultrasonic testing and designing Transducers, pulser / signal generator, amplifiers, switches, oscilloscope Pressure generating Heating Pressure monitoring Temperature monitoring Transducer cooling Ordering parts Planning the measurement procedure Assembling the setup Programming the DAQ software 7.12.2007 Ilkka Lassila Validation Device: Vp and Vs 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 Caused mode well present by silver epoxy? Removable delay lines Fused quartz Brass Water cooling No load over the piezo crystal 7.12.2007 Ilkka Lassila Device: pressure simulation Pressure simulations by Mr. Haapalainen Device Fused can withstand the required pressure quartz can be used as a delay line material in case of no roughness 7.12.2007 Ilkka Lassila Device: pressure Generating: 15 ton jack borrowed from Department of Chemistry Measuring: Sensotec Model 53 (max 23 ton) + Lebow 7528 amplifier 7.12.2007 Ilkka Lassila Device: pressure Problem with sample durability Solved with a brass jacket Splitting sample holder allows sample removal after compression 7.12.2007 Ilkka Lassila Device: Temperature, simulations 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 7.12.2007 Ilkka Lassila Device: Temperature 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 7.12.2007 Ilkka Lassila Thermocouple inside the sample holder Device: Data acquisition US signals: 5072 PR, LeCroy 9410, GPIB, PC, LabVIEW, Matlab Thermocouple and load cell: AD-conversion 7.12.2007 Ilkka Lassila and transfer to PC with NI PCI-6024E Device Transducers Delay lines Heating element and sample Thermocouple Load cell Water cooling tubes Jack 7.12.2007 Ilkka Lassila Preliminary results 7 samples from Outokumpu Deep Drill Core T: 300ºC20ºC, Load: 7000 kg 500 kg (resembling the conditions in the Earth’s crust) Results comparable with literature values 4000 5500 Vs(m/s) Vp(m/s) 6000 5000 4500 4000 0 7.12.2007 Ilkka Lassila 3500 3000 0.5 1 1.5 T*load(ºC kg) 2 6 x 10 0 0.5 1 1.5 T*load(ºC kg) 2 6 x 10 Pressure test Pressure test without sample 49.3 the compression of the sample? Compression = 0,1 mm (Δhsample- Δhno sample) Error Vp = 24-33 m/s Error Vs = 15-18 m/s measured height (mm) The error if we don’t measure 49.2 49.1 49 1000 kg 13000 kg 48.9 48.8 48.7 48.6 Pressure test with sample 71.3 measured height (mm) 71.2 71.1 71 70.9 70.8 70.7 70.6 70.5 7.12.2007 Ilkka Lassila 1000 kg 13000 kg TOF (time of flight) through the delay lines 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 7.12.2007 Ilkka Lassila Damping the transducers 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 7.12.2007 Ilkka Lassila Egypt. J. Sol., Vol. (23), No. (2), (2000) Damping test - ok Reduced ringing time and increased bandwidth 7.12.2007 Ilkka Lassila Transducers without backing 7.12.2007 Ilkka Lassila Outcome of applying the backing 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 7.12.2007 Ilkka Lassila New transducers 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: No 7.12.2007 Ilkka Lassila stainless steel separate delay lines New transducer drawings 7.12.2007 Ilkka Lassila New transducer 7.12.2007 Ilkka Lassila New thermal simulations T=? T=10ºC 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) 7.12.2007 Ilkka Lassila h = 20-70mm T(t=0)=350ºC D = 25-62 mm Temperature as a function of time in the middle of the sample and on the transducer inner surface where the piezos are fixed. Sample D = 25,5 mm, h = 24 mm 7.12.2007 Ilkka Lassila Sample D = 62 mm, h = 70 mm Temperature distribution in the sample and the upper transducer Sample D = 25,5 mm, h = 24 mm t = 200s. 7.12.2007 Ilkka Lassila Sample D = 62 mm, h = 70 mm, t = 400s. Other updates PC controlled pressure generation Separate heating of samples to increase the throughput rate 7.12.2007 Ilkka Lassila New frame Compressed air controlled one way hydraulic cylinder replaced with electric motor controlled two way hydraulic cylinder 7.12.2007 Ilkka Lassila Modification for hydraulic control 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 7.12.2007 Ilkka Lassila closed no change Testing new hydraulics Pressure increase at 0,1 s intervals OK for loads over 3000 kg 9000 8000 load (kg) 7000 6000 5000 4000 3000 2000 1000 0 0 0,5 1 1,5 throttle time (s) 7.12.2007 Ilkka Lassila 2 2,5 3 Testing of new hydraulics Pressure decrease at 0,1 s intervals No control of outcome when decreasing pressure 14000 12000 load (kg) 10000 8000 6000 4000 2000 0 -2000 0 0,05 0,1 0,15 throttle time (s) 7.12.2007 Ilkka Lassila 0,2 0,25 More control needed Manual shut off valve, needle type control Slows down the flow of the hydraulic oil 7.12.2007 Ilkka Lassila Control achieved Needle valve can be adjusted to allow precise control of the load 7,00E+03 8,00E+03 7,00E+03 5,00E+03 4,00E+03 3,00E+03 2,00E+03 target load 5,00E+03 load (kg) load (kg) 6,00E+03 6,00E+03 measured load 4,00E+03 3,00E+03 2,00E+03 1,00E+03 1,00E+03 0,00E+00 0,00E+00 7.12.2007 Ilkka Lassila measured load target load Measurement diagram 7.12.2007 Ilkka Lassila Conclusions 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 7.12.2007 Ilkka Lassila Future tasks 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 7.12.2007 Ilkka Lassila