Seismic Exploration of Hydrocarbons in Heterogeneous Reservoirs (eBook)

New Theories, Methods and Applications

Jing Ba, Jose M. Carcione, Qizhen Du, Tobias Muller, Haibo Zhao (Autoren)

eBook Download: EPUB

2014 | 1. Auflage
370 Seiten
Elsevier Science (Verlag)
978-0-12-420205-4 (ISBN)

Infos

Seismic Exploration of Hydrocarbons in Heterogeneous Reservoirs: New Theories, Methods and Applications is based on the field research conducted over the past decade by an authoring team of five of the world's leading geoscientists. In recent years, the exploration targets of world's oil companies have become more complex. The direct detection of hydrocarbons based on seismic wave data in heterogeneous oil/gas reservoirs has become a hot spot in the research of applied and exploration geophysics. The relevant theories, approaches and applications, which the authors have worked on for years and have established mature technical processes for industrial application, are of significant meaning to the further study and practice of engineers, researchers and students in related area. - Authored by a team of geophysicists in industry and academia with a range of field, instruction, and research experience in hydrocarbon exploration - Nearly 200 figures, photographs, and illustrations aid in the understanding of the fundamental concepts and techniques - Presents the latest research in wave propagation theory, unconventional resources, experimental study, multi-component seismic processing and imaging, rock physics modeling and quantitative seismic interpretation - Sophisticated approach to research systematically forms an industrial work flow for geoscience and engineering practice

Jing Ba was born in Hubei province of China in 1980. He received his doctoral degree from one of Chinese top universities, Tsinghua University in 2008. From 2008 to 2012, He worked as a geophysicist in the Research Institute of Petroleum Exploration & Development (RIPED), China National Petroleum Corporation (CNPC). He was employed as a senior geophysicist by CNPC in 2012 and also works as a geophysical consultant for Energy Prospecting Technology USA Inc. (USA) in part-time service. He is an associate editor of Applied Geophysics since 2011 and works as technical referee for more than 20 geophysical journals. He is a member of AGU, SEG and EAGE. With solid and strong researching and application experiences in China, Central Asia and South America, he has been dedicated to build vast cooperation relationships between oil companies, oil service companies and global top-rated universities and researching institutes. He is also always ready to be a bond of both academic and practical connections between world and Chinese exploration communities. Jing Ba published 2 books and more than 60 articles on geophysical journals and key conferences. His main research interests are wave propagation theory and hydrocarbon seismic detection methods. He leads several key research projects of wave propagation theory and industrial application. His theories and techniques have been successfully applied in the exploration areas of oil fields of China. He won several prizes for exploration research and has presented 11 China patents.

Textauszug

Chapter 2

Wave Propagation and Attenuation in Heterogeneous Reservoir Rocks

Jing Ba1

Zhenyu Yuan2

José M. Carcione3

Yuqian Guo4

Lin Zhang2

Weitao Sun5
1    Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas, US
2    School of Geosciences, China University of Petroleum (East China), Qingdao, Shandong, China
3    Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste, Italy
4    Institute of Geomechanics, Chinese Academy of Geological Sciences, Xicheng, Beijing, China
5    Zhou Pei-Yuan Center for Applied Mathematics, Tsinghua University, Haidian, Beijing, China

Abstract

In order to investigate wave propagation in heterogeneous reservoir rocks, the equations of wave motion in a fluid-saturated double-porosity medium are derived based on Biot’s theory of poroelasticity and a generalization of Rayleigh’s theory of fluid collapse to the porous case, namely the Biot–Rayleigh Theory. The theory assumes a porous inclusion embedded in a porous host medium. Two cases are considered based on the Biot–Rayleigh equations, namely a double-porosity solid saturated with a single fluid and a single-porosity solid saturated with two immiscible fluids. The fluid kinetic energy of the spherical inclusions contributes to the local-flow kinetic energy and dissipation function. The local fluid-flow velocity fields inside and outside the inclusions are derived, leading to the kinetic energy function and dissipation function, rederived on the basis of the Biot–Rayleigh theory. Examples comparing the wave-propagation theories and experimental measurements are given for different types of rocks and fluids. By considering ultrasonic measurements on reservoir rocks that are partially saturated with oil and brine, the fluid substitution effects are studied in the analysis with Biot’s poroelasticity.

Keywords

wave propagation

attenuation

velocity dispersion

heterogeneous

reservoir rocks

poroelasticity

partial saturation

ultrasonic measurements

Chapter Outline

2.1 Introduction 9

2.2 Biot–Rayleigh Theory of Wave Propagation in Heterogeneous Porous Media 10

2.3 Biot–Rayleigh Theory of Wave Propagation in Patchy- Saturated Reservoir Rocks 21

2.4 Wave Propagation in Partially Saturated Rocks: Numerical Examples 26

2.4.1 Influence of Fluid Composition 26

2.4.2 Influence of Fluid Mobility 28

2.4.3 Influence of the Fluid Compressibility Ratio 31

2.4.4 Influence of Rock Porosity 31

2.4.5 Influence of Saturation Degree 32

2.5 Effect of Inclusion Pore-Fluid: Reformulated Biot–Rayleigh Theory 33

2.6 Fluid Substitution in Partially Saturated Sandstones 37

Acknowledgments 42

References 42

2.1. Introduction

The mechanism of local fluid flow explains the high attenuation and dissipation of low-frequency seismic waves in fluid-saturated reservoir rocks. When acoustic waves propagate through small-scale heterogeneities, pressure gradients are induced between regions of dissimilar properties. The mesoscopic-scale length of the heterogeneity is intended to be larger than the grain size, but much smaller than the wavelength of pulse. If the matrix compressibility varies significantly, diffusion of the pore fluid between different regions constitutes a mechanism that is important at seismic frequencies.

An attempt to introduce squirt-flow effects has been presented by Dvorkin et al. (1995) in a microscopic scale, in which a force applied to the area of contact between two grains produces a displacement of the surrounding fluid in and out of this area. White (1975) and White et al. (1975) were the first to introduce the mesoscopic loss mechanisms based on poroelasticity. Gas pockets in a water-saturated porous medium and porous layers alternately saturated with water and gas are considered, respectively. These are the so-called “patchy saturation” models. The mesoscopic-loss theory has been further studied by Shapiro and Müller (1999), Johnson (2001), Müller and Gurevich (2004), and Pride et al. (2004).

Johnson (2001) developed a model for patches of arbitrary shape, which has two geometrical parameters: the specific surface area and the size of the patches. Murphy (1982) and Knight and Nolen-Hoeksema (1990) have observed the patchy saturation effects on acoustic properties. Cadoret et al. (1995) investigated the relevant phenomenon in the laboratory at the frequency range 1–500 kHz, and the results showed that two different saturation methods result in different fluid distributions and produce two dissimilar values of velocity for the same saturation degree.

Generalization of Biot’s theory to a composite or a double-porosity medium is generally based on Biot’s poromechanical approach by using Lagrange’s equations (Biot, 1962). Berryman and Wang (2000) derived phenomenological equations for the poroelastic behavior of a double-porosity medium to account for storage porosity and fracture porosity in oil/gas reservoirs. Another Biot-type poroelasticity theory describes the mesoscopic loss generated by lithological patches having different degrees of consolidation (Pride et al., 2004). Ba et al. (2008a) and Ba et al. (2008b) have solved the double-porosity governing equations and simulated the wavefields by using the pseudo-spectral method. Liu et al. (2009) solved equivalent poroviscoacoustic equations by approximating the mesoscopic complex moduli in the frequency domain using Zener mechanical models.

In this chapter, we develop a new double-porosity theory, namely the Biot–Rayleigh theory, based on Biot’s theory of poroelasticity and a generalization of Rayleigh’s theory of fluid collapse to the porous case. We further generalize it to the case of a single-porosity solid saturated with two immiscible fluids. By analyzing the influence of the local fluid-flow velocity fields in the inclusion, the poroelasticity theories are reformulated when the fluid kinetic energy of the inclusions cannot be neglected (it is the case in heterogeneous oil/water reservoirs). Comparisons are performed between the theoretical predictions and experimental measurements and fluid substitution effects in actual rocks are discussed.

2.2. Biot–Rayleigh Theory of Wave Propagation in Heterogeneous Porous Media

For a double-porosity medium as shown in Figure 2.1, wave propagation induces local fluid flow (LFF) between the inclusions and the host medium due to the different compressibilities. For the purpose of describing the wave-induced LFF, we assume that LFF occurs between soft and stiff pores. We then propose a double-porosity approach by using a generalization of Rayleigh’s theory of liquid collapse of a spherical cavity in the framework of Biot’s poromechanics (Biot, 1962).

Figure 2.1 Synoptic diagram showing four types of double-porosity media in nature. (A) Flat throats connected to stiff pores at a microscopic scale. (B) Patches of small grains embedded in a matrix formed of large grains. (C) Strongly dissolved dolomite, in which powder crystals are present in the pores forming a second matrix. (D) Partially melted ice matrix, whose pores are filled with a mixture of loosely contacted micro-ice crystals and water.

In order to describe quantitatively the dynamical process of wave-induced LFF in heterogeneous fluid/solid composites, the dynamical governing equations are derived from first principles. First, the kinetic energy expression is derived by considering a spherical inclusion imbedded in a uniform porous host medium. Then, the kinetic energy and strain potential energy functions are combined with Lagrange equations, and three dynamical equations are obtained describing wave propagation. We derive the relevant stiffness coefficients by performing “gedanken experiments.” Then, analyses of plane-wave solutions are conducted to obtain the phase velocity and quality factor as a function of frequency.

We consider the inclusion model shown in Figure 2.2, with the following assumptions: (1) The inclusions are spherical, homogeneous and of the same size; (2) the boundary conditions between the inclusions and the host medium are open; (3) the radius of the inclusion is much smaller than the wavelength; and (4) the inclusion volume ratio is low, so the interaction between inclusions can be neglected. Assume that R0 is the radius of the (spherical) inclusion at rest, and R is the dynamical radius of the fluid sphere after the LFF process (see Figure 2.2), which is a function of time. The inclusions and host...

Produkt-Details

• Erscheint lt. Verlag: 2.5.2014
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geografie / Kartografie
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geologie
• Themenwelt: Technik ► Bergbau
• ISBN-10: 0-12-420205-5 / 0124202055
• ISBN-13: 978-0-12-420205-4 / 9780124202054