Location

La Jolla, CA

Start Date

1-1-1998 12:00 AM

Description

Understanding and predicting the effects of surface roughness on ultrasonic pulse-echo measurements is important in a variety of applications. In particular, it is of interest for cased well evaluation in the oilfield industry where the measurement is used to investigate the cement seal placed between the casing and the formation wall (see Fig. 1(a)) [1]. Here, the acoustic transducer signal arises from multiple reflections taking place at the various interfaces of the layered (borehole fluid)-(steel casing)-cement-(rocky formation) structure. Previous numerical models, developed to account for this measurement, have been limited to canonical configurations where, in particular, the various interfaces are smooth [2]. Typically, the cement-formation interface is rough with widely varying rms height and correlation length. In order to predict the effect of roughness of arbitrary sizeon the reflection echo attributed to this interface, a frequency-domain hybrid analytical/numerical simulation model has been developed. The model has been preliminary implemented for a two-dimensional (2D) configuration where an acoustic transducer with a Gaussian profile interacts with the aforementioned structure in a planar geometry (see Fig. 1(b)). In this configuration, the transducer aperture has a finite size in the (x, z) and is infinite in the y direction. The fluid, steel layer, cement layer, and halfspace formation are assumed to be isotropic and homogeneous. The cement-formation interface, denoted by S 0, is in general irregular or rough and parameterized by the function z = h(x) describing the height of a particle on S 0 measured from the (mean) plane z = 0. A time-harmonic variation e iωt is assumed throughout.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

17A

Chapter

Chapter 1: Standard Techniques

Section

Elastic Wave Scattering/Backscattering

Pages

81-88

DOI

10.1007/978-1-4615-5339-7_10

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

A 2D Hybrid Model for Ultrasonic Pulse-Echo Scattering from a Rough Interface Buried in a Layered Medium

La Jolla, CA

Understanding and predicting the effects of surface roughness on ultrasonic pulse-echo measurements is important in a variety of applications. In particular, it is of interest for cased well evaluation in the oilfield industry where the measurement is used to investigate the cement seal placed between the casing and the formation wall (see Fig. 1(a)) [1]. Here, the acoustic transducer signal arises from multiple reflections taking place at the various interfaces of the layered (borehole fluid)-(steel casing)-cement-(rocky formation) structure. Previous numerical models, developed to account for this measurement, have been limited to canonical configurations where, in particular, the various interfaces are smooth [2]. Typically, the cement-formation interface is rough with widely varying rms height and correlation length. In order to predict the effect of roughness of arbitrary sizeon the reflection echo attributed to this interface, a frequency-domain hybrid analytical/numerical simulation model has been developed. The model has been preliminary implemented for a two-dimensional (2D) configuration where an acoustic transducer with a Gaussian profile interacts with the aforementioned structure in a planar geometry (see Fig. 1(b)). In this configuration, the transducer aperture has a finite size in the (x, z) and is infinite in the y direction. The fluid, steel layer, cement layer, and halfspace formation are assumed to be isotropic and homogeneous. The cement-formation interface, denoted by S 0, is in general irregular or rough and parameterized by the function z = h(x) describing the height of a particle on S 0 measured from the (mean) plane z = 0. A time-harmonic variation e iωt is assumed throughout.