Acoustic detection of stress-induced mechanical damage in a borehole wall
First Claim
1. A method for locating and measuring mechanical damage in rock surrounding a borehole in a formation, the method comprising:
- a) measuring ultrasonic compressional wave velocity and ultrasonic compressional wave amplitude in a portion of a borehole wall at a plurality of azimuths using pulses of waves having frequencies above 25 kHz to produce at each of the plurality of azimuths an ultrasonic compressional wave velocity value and an ultrasonic compressional wave energy value; and
b) identifying at least one local energy maximum in the ultrasonic energy values.
1 Assignment
0 Petitions
Accused Products
Abstract
A method provides for locating and measuring mechanical damage in rock surrounding a borehole by detecting one or both of reductions in ultrasonic compressional wave velocity in the rock as a function of azimuth, and by detecting focused acoustic energy in the rock from local increases in ultrasonic compressional wave amplitude resulting from velocity gradients. A first preferred embodiment uses a combination of azimuthal ultrasonic compressional wave velocity data and azimuthal ultrasonic compressional wave energy data. A second embodiment uses azimuthal ultrasonic compressional wave velocity data and omni-directional sonic velocity data, with a comparison test or a curve fitting test. A third embodiment uses azimuthal ultrasonic compressional wave energy data.
45 Citations
17 Claims
-
1. A method for locating and measuring mechanical damage in rock surrounding a borehole in a formation, the method comprising:
-
a) measuring ultrasonic compressional wave velocity and ultrasonic compressional wave amplitude in a portion of a borehole wall at a plurality of azimuths using pulses of waves having frequencies above 25 kHz to produce at each of the plurality of azimuths an ultrasonic compressional wave velocity value and an ultrasonic compressional wave energy value; and
b) identifying at least one local energy maximum in the ultrasonic energy values. - View Dependent Claims (2, 3, 4, 5, 6, 7)
c) identifying a direction of maximum stress; and
d) defining the direction of maximum stress as 0 degrees;
wherein identifying at least one local energy maximum includes identifying local energy maxima at 90 degrees and 270 degrees.
-
-
7. A method according to claim 1, wherein measuring ultrasonic compressional wave velocity in a portion of a borehole wall includes measuring ultrasonic compressional wave velocity using a pair of first and second receivers.
-
8. A method for locating and measuring mechanical damage in rock surrounding a borehole in a formation, the method comprising:
-
a) measuring ultrasonic compressional wave velocity using directional pulses of waves having frequencies above 25 kHz in a portion of the borehole wall at a plurality of azimuths to produce a set of ultrasonic compressional wave velocity values;
b) measuring sonic velocity in the formation beyond the borehole wall using omni-directional sonic waves to produce a velocity value; and
c) comparing the set of ultrasonic compressional wave velocity values with the sonic velocity value. - View Dependent Claims (9, 10, 11)
-
-
12. A method for locating and measuring mechanical damage in rock surrounding a borehole in a formation, the method comprising:
-
a) measuring ultrasonic compressional wave velocity using directional pulses of waves having frequencies above 25 kHz in a portion of the borehole wall at a plurality of azimuths to produce a set of ultrasonic compressional wave velocity values;
b) curve fitting the set of ultrasonic compressional wave velocity values with a sine wave; and
c) testing the curve fit for indication of damage. - View Dependent Claims (13, 14, 15)
d) measuring sonic velocity in the formation beyond the borehole wall using omni-directional sonic waves to produce a set of sonic velocity values; and
e) testing for ultrasonic compressional wave velocities less than the sonic velocities at most azimuths as indication of damage.
-
-
16. A method for locating and measuring mechanical damage in rock surrounding a borehole in a formation, the method comprising:
-
a) measuring ultrasonic compressional wave energy amplitude of waves having frequencies above 25 kHz in a portion of a borehole wall at a plurality of azimuths to produce at each of the plurality of azimuths an ultrasonic compressional wave energy amplitude value; and
b) identifying pairs of amplitude maxima spaced at approximately 90 degrees as indication of damage. - View Dependent Claims (17)
c) identifying a direction of maximum stress;
d) defining the direction of maximum stress at 0 degrees; and
e) locating damage at 0 degrees.
-
Specification