1991 Fiscal Year Final Research Report Summary
Development of Wideband Downhole Triaxial Seismic Detector
| Project/Area Number |
02555084
|
|---|
| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
計測・制御工学
|
|---|
| Research Institution | Tohoku University |
|---|
Principal Investigator |
NIITSUMA Hiroaki Faculty of Engineering, Tohoku University, 工学部, 教授 (90108473)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
SAEKI Akio Tohoku Electronic Industrial co. Ltd., 社長
ABE Mamoru Faculty of Engineering, Tohoku University, 工学部, 助教授 (50005310)
SATO Motoyuki Faculty of Engineering, Tohoku University, 工学部, 助教授 (40178778)
|
|---|
| Project Period (FY) |
1990 – 1991
|
| Keywords | Downhole Measurement / Seismic Measurement / AE Measurement / Crosshole Measurement / Triaxial Deterctor / Geothermal Development / Hot Dry Rock / Inner Space Technology |
|---|
| Research Abstract |
We have developed a downhole triaxial sonde, which consist of cable head, an electronic circuit package, a transducer housing and two-arm mechanical fixcers. The fixers are set at the upper and lower parts of the sonde. Thesonde was designed for the maximum operating temperature of 150ﾟC and pressure of 20 MPa. A shear-mode piezoelectric triaxial accelerometer has been developed and calibrated. The cross sensitivity between three components os less than 2 %, while the absolute sensitivity is 2000 pC/g. An electronic compass, in which a hall device is rotated by a motor driven potentiometer, and preamplifiers have also been developed. Overall sensitivity and frequency range are 3.16 V/g and 7-1000 Hz, re- spectively.
A new calibration method for the downhole triaxial detector has also been developed. Detectability of the three dimensional particle motion associated with the seismic wave is reasonably estimated in a frequency and time domain by using the spectral matrix analysis. The method has been applied to the in-situ calibration test of the sonde in Higashi Hachimantai field, where downhole air gun was employed as a wave source. The particle motion direction at the onset of the P-wave and the effect of resonance against that were quantitavely evaluated as a function of both time and frequency. The in-situ cross sensitivity of the sonde has also been estimated by the method. The feasibility of the new measurement system was confirmed in field AE measurements of geothermal reservoir.
|
