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Über dieses Buch

This book covers the principles, historical development, and applications of many acoustic logging methods, including acoustic logging-while-drilling and cased-hole logging methods. Benefiting from the rapid development of information technology, the subsurface energy resource industry is moving toward data integration to increase the efficiency of decision making through the use of advanced big data and artificial intelligence technologies, such as machine/deep learning. However, wellbore failure may happen if evaluations of risk and infrastructure are made using data mining methods without a complete understanding of the physics of borehole measurements. Processed results from borehole acoustic logging will constitute part of the input data used for data integration. Therefore, to successfully employ modern techniques for data assimilation and analysis, one must fully understand the complexity of wave mode propagation, how such propagation is influenced by the well, and the materials placed within the well (i.e., the cement, casing, and drill strings), and ultimately how waves penetrate into and are influenced by geological formations.

State-of-the-art simulation methods, such as the discrete wavenumber integration method (DWM) and the finite difference method (FDM), are introduced to tackle the numerical challenges associated with models containing large material contrasts, such as the contrasts between borehole fluids and steel casings. Waveforms and pressure snapshots are shown to help the reader understand the wavefields under various conditions. Advanced data processing methods, including velocity analyses within the time and frequency domains, are utilized to extract the velocities of different modes. Furthermore, the authors discuss how various formation parameters influence the waveforms recorded in the borehole and describe the principles of both existing and potential tool designs and data acquisition schemes.

This book greatly benefits from the research and knowledge generated over four decades at the Earth Resources Laboratory (ERL) of the Massachusetts Institute of Technology (MIT) under its acoustic logging program.

Given its scope, the book is of interest to geophysicists (including borehole geophysicists and seismologists), petrophysicists, and petroleum engineers who are interested in formation evaluation and cementation conditions. In addition, this book is of interest to researchers in the acoustic sciences and to 4th-year undergraduate and postgraduate students in the areas of geophysics and acoustical physics.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
Well logging is extensively employed within boreholes to obtain high-resolution physical measurements and determine the properties of the subsurface. Accordingly, well logging constitutes one of the key technologies in the oil and gas industry, but it also has applications in hydrology, environmental geoscience and geotechnical research. The information acquired through well logging complements surface measurements by providing high-resolution subsurface data; these borehole measurements provide detailed geological, petrophysical, and fluid properties under in situ conditions with continuous depth coverage.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Chapter 2. Wave Propagation in an Open Borehole

Abstract
This chapter covers theoretical/numerical modeling of wave propagation in an open (uncased) borehole. It starts with the analytical formulation of seismic wave propagation and proceeds to modeling for boreholes in formations with different velocities and for different source types (monopole, dipole, and quadrupole). Numerical calculations provide an extensive suite of examples that illustrate the sensitivity of the acoustic logs to formation properties, borehole radii, and type and frequency of the sources. Field data examples are also included to illustrate the waveforms in different formations.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Chapter 3. Data Processing Methods for Borehole Acoustics

Abstract
Borehole acoustic data need to be processed to determine the formation waves’ velocity. Here we present some of the most commonly used methods to extract the different modes and to determine the formation velocities. In the early history of acoustic logging, where there were a few receivers in the array, the arrival times were used for velocity determination. With digital recording and expanded arrays, elaborate methods were developed.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Chapter 4. Wave Propagation in a Cased Borehole and Cement Bond Evaluation

Abstract
In many boreholes, casing is used and cemented to seal the borehole wall and to stabilize the borehole. Figure 4.1 shows a schematic diagram of a cased hole. The annulus between the casing and formation may be filled with fluid or cement. Table 4.1 lists the geometrical and elastic parameters of a well-cemented cased hole model.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Chapter 5. Acoustic Logging-While-Drilling

Abstract
Acoustic logging-while-drilling (ALWD) is an advanced technology developed to determine the formation properties in real-time while drilling. Its advantages include obtaining formation properties while conserving drill-rig time, true formation information without invasion, acquisition of information for drilling safety such as over-pressured formations, and for geo-steering.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Chapter 6. Effects of Tool Eccentricity on Acoustic Logs

Abstract
In real measurement, the tool axis may not perfectly align with the borehole axis even with centralizers due to drill string movements. In this chapter, the wavefields of an eccentered tool in both wireline and acoustic logging-while-drilling cases are discussed. Influence of the tool eccentering on formation wave velocity measurement and methods to estimate the tool position in the borehole are covered.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Chapter 7. Peripheral Imaging Around a Borehole

Abstract
Imaging around a borehole provides valuable information for high-resolution characterization of the subsurface. Surface seismic surveys provide good lateral imaging, but its capabilities for detecting small features are limited. Conventional borehole acoustic logging, described in Chap. 2, has a lateral depth of investigation of approximately one meter from the borehole.
Hua Wang, M. Nafi Toksöz, Michael C. Fehler

Backmatter

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