US 2007/0183259 A1 · Borehole apparatus and methods for simultaneous multimode excitation and reception to determine elastic wave velocities, elastic modulii, degree of anisotropy and elastic symmetry configurations

Abstract

An acoustic borehole logging system for generation and detection of multipole modes used to determine elastic properties of earth formations characterized as inhomogeneous anisotropic solids. The system concurrently generates and senses monopole, dipole, quadrupole and any higher order pole in the borehole/formation system in order to characterize the elastic properties and stress state of material penetrated by the borehole. Multipole modes of all orders are induced simultaneously without the need for separate transmitter and receiver systems. Performance of the logging system is not compromised due to eccentering of the axis of the tool in the borehole, tool tilt with respect to the axis of the borehole, or mismatch of response sensitivity of multiple receivers within the tool. The system comprises apparatus for generating and sensing acoustic signals in a borehole in an earth formation, and further comprises a processing method by which the sensor response signals are processed and analyzed to obtain desired formation parameters of interest.

Claims19

Dependent claims

A system for measuring a property of borehole environs comprising a formation penetrated by a borehole, said system comprising:

(a) a tool conveyable within said borehole;
(b) an acoustic transmitter disposed within said tool, wherein
(i) said transmitter transmits an asymmetric acoustic pulse into said borehole environs, and
(ii) said acoustic pulse generates a plurality of acoustic modes within said borehole environs;
and
(c) an acoustic receiver array disposed within said tool and axially displaced from said transmitter;
wherein
(i) said receiver array comprises at least two receiver stations at different axial spacings from said transmitter,
(ii) each said station responds, at a plurality of azimuthal positions, to said modes generated by said transmitter,
(iii) said responses are combined using angular decomposition to simultaneously identify said modes, and
(iv) said identified modes are used to determine said property.

8 more elements

A method for determining a geophysical property of a material from response of a receiver array to simultaneously generates multiple acoustic mode components within said material by an asymmetric pulse of acoustic radiation, said method comprising:

(a) finely sampling and digitizing said receiver array response to avoid temporal and spatial aliasing;
(b) from said response, simultaneously identifying by angular decomposition phases components propagating over said receiver array into said multiple acoustic modes;
(c) calculating velocity of each of said mode component;
(d) identifying types of wave forms components for each said mode;
(e) defining elastic constants for an elastic material having triclinic symmetry;
(f) using results of steps (c), (d) and (e) to determine said elastic constants for said material thereby determining said geophysical property of said material.

3 more elements

Dependencies are inferred from the claim text.

Borehole apparatus and methods for simultaneous multimode excitation and reception to determine elastic wave velocities, elastic modulii, degree of anisotropy and elastic symmetry configurations

Life of this patent

Borehole apparatus and methods for simultaneous multimode excitation and reception to determine elastic wave velocities, elastic modulii, degree of anisotropy and elastic symmetry configurations

Life of this patent

Abstract

Claims19