Feasibility of using sonic techniques to estimate in-situ stresses
This report presents the results of a three-year research effort to develop a technique for estimating in situ stresses by measuring stress-induced velocity anisotropy around a borehole. Relevant parameters required to make the estimate were identified and measured in the laboratory on a 35.6-cm cube of Nugget sandstone with a 10.2-cm diameter hole, under biaxial loading. The major technical obstacle to this study was the design of a transducer system for generating radially and tangentially polarized shear waves in a borehole configuration; the final design utilized a transducer/wedge assembly to generate refracted waves. Two pairs each of radially and tangentially polarized transducers were placed inside the 10.2-cm hole with displacement directions either parallel or perpendicular to the principal stress directions. With this configuration, relative travel times were measured by both a pulsed phase-locked loop technique and a cross correlation of digitized waveforms. Results from each technique show very good agreement, which indicates the validity of the approach. The uncertainty of timing was about 0.03 ..mu..s for an individual file. The biaxial test data were used to calculate the applied stress. The standard deviation of the differences between the calculated and applied stresses is 0.62 MPa for a stress level up to 8.63 MPa. Based on the success of the laboratory measurement, the authors recommend that this research be pursued towards implementing a field procedure for estimating in situ stresses. 26 references.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5926206
- Report Number(s):
- UCRL-53424; ON: DE83016890
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SANDSTONES
STRESSES
MEASURING METHODS
ANISOTROPY
BENCH-SCALE EXPERIMENTS
BOREHOLES
EXPERIMENTAL DATA
FEASIBILITY STUDIES
SEISMIC S WAVES
VELOCITY
CAVITIES
DATA
INFORMATION
NUMERICAL DATA
ROCKS
SEDIMENTARY ROCKS
SEISMIC WAVES
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)