Time Lapse Approach to Monitoring Oil, Gas, and CO2 Storage by Seismic Methods

By Junzo Kasahara and Yoko Hasada

Time Lapse Approach to Monitoring Oil, Gas, and CO2 Storage by Seismic Methods delivers a new technology to geoscientists, well logging experts, and reservoir engineers, giving them a new basis on which to influence decisions on oil and gas reservoir management.

Named ACROSS (Accurately Controlled and Routinely Operated Signal System), this new evaluation method is presented to address more complex reservoirs, such as shale and heavy oil. The book also discusses prolonged production methods for enhanced oil recovery. The monitoring of storage zones for carbon capture are also included, all helping the petroleum and reservoir engineer to fully extend the life of a field and locate untapped pockets of additional oil and gas resources. Rounded out with case studies from locations such as Japan, Saudi Arabia, and Canada, this book will help readers, scientists, and engineers alike to better manage the life of their oil and gas resources and reservoirs.

• Benefits both geoscientists and reservoir engineers to optimize complex reservoirs such as shale and heavy oil
• Explains a more accurate and cost efficient reservoir monitoring technology called ACROSS (Accurately Controlled and Routinely Operated Signal System)
• Illustrates real-world application through multiple case studies from around the world

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 14, 2016
• ISBN: 9780128036099

Junzo Kasahara

Junzo Kasahara received B. S., M.S., and D.Sc. degrees in Geophysics from Nagoya University in 1965, 1967, and 1970, respectively. Between 1970 -1986 and 1988-2004, he was the assistant, associate, and full professors at the university of Tokyo. He worked in marine seismology. During 1974,1976, and in 1979, was the visiting associate professor of University of Hawaii. In 1986, he joined Schlumberger Japan as manager for seismic interpretation and the logging tool design. During his academic works, he published three books from the University of Tokyo Press. He was awarded the professor of emeritus of the University of Tokyo. In 2004, he joined Tono Geoscience Center as a senior researcher, where he worked on the ACROSS project. Between 2004 and 2008, he served for the extension of the Japan Continental Shelf. Currently, he is the principal investigator for the geothermal project and visiting professor at the University of Shizuoka.

Book preview

Time Lapse Approach to Monitoring Oil, Gas, and CO2 Storage by Seismic Methods

Junzo Kasahara

Tokyo University of Marine Science and Technology, Shizuoka University

Yoko Hasada

Daiwa Exploration and Consulting Co., Ltd.

Table of Contents

Cover image

Title page

Copyright

Preface

Acknowledgments

Chapter 1. What is Time Lapse?

1.1. Introduction

1.2. Overview of Time-Lapse Studies

1.3. Objectives of Time-Lapse Studies

1.4. Brief Review of Previous Approaches for the Time-Lapse Studies

1.5. Factors Affecting the Time-Lapse Study

1.6. Summary of Time-Lapse Approaches

Chapter 2. Various Time-Lapse Methods

2.1. 4D Seismic Method

2.2. Cross-Hole Seismic Tomography and Vertical Seismic Profile

2.3. Well Loggings

2.4. Ocean Bottom Cable/Ocean Bottom Seismometer for Permanent Reservoir Monitoring

2.5. Interferometric Synthetic Aperture Radar and Seismic Interferometry

2.6. Distributed Temperature Sensor

Chapter 3. Active Seismic Approach by Accurately Controlled and Routinely Operated Signal System

3.1. Uniqueness of the Accurately Controlled and Routinely Operated Signal System (ACROSS) Approach

3.2. Outline of the ACROSS Seismic Source System (See Appendix B for Details)

3.3. Outline of the ACROSS Data Processing

Chapter 4. Imaging of Temporal Changes by Backpropagation

4.1. Backprojection

4.2. Backpropagation Method for the Time-Lapse Imaging

4.3. Ketzin CO2 Storage Case

4.4. Oil Sands in Canada

4.5. Simulation of Reservoir at 2 km Depth

4.6. Simulation of Very Shallow Reservoir

Chapter 5. Passive Seismic Approach

5.1. Separation of Passive (Background) Signal From Active (Vibrator) Signal

5.2. Microseismics

5.3. Seismic Interferometry

Chapter 6. Previous Time-Lapse Studies Other Than Accurately Controlled and Routinely Operated Signal System Method

6.1. Nagaoka CCS Pilot

6.2. Weyburn-Midale Region (The International Energy Agency Greenhouse Gas Weyburn-Midale CO2 Monitoring and Storage Project)

6.3. In Salah

6.4. CO2-CRC Otway Project

6.5. Sleipner

6.6. Permanent Reservoir Monitoring

6.7. Other Areas

Chapter 7. Case Studies Based on Accurately Controlled and Routinely Operated Signal System Methodology

7.1. Case Studies in Japan

7.2. Air Injection Experiment in Awaji Island

7.3. Time-Lapse Experiment Using Modified Conventional Seismic Source to Evaluate the Near-Surface Effects

7.4. Field Test in Saudi Arabia

Chapter 8. Near-Surface Effects

8.1. Effect of Precipitation

8.2. Effect of Temperature

8.3. Ground Rolls (Surface Wave) Effects

Chapter 9. Repeatability

9.1. Factors Controlling Repeatability

9.2. Normalized Root Mean Square and Predictability

9.3. Source Signature Repeatability

9.4. Ground Coupling

9.5. Structure Between Source(s) and Receivers

9.6. Geophones

9.7. Positions of Source(s) and Reviser(s)

9.8. Time Base and Digitizing Resolution

9.9. Ambient Noise

9.10. Repeatability of ACROSS Source

Chapter 10. Rock Physics

10.1. Physical Properties of Porous Media

10.2. Effects of Shape of Pore

10.3. VP and VS Including Liquid

10.4. Effects of Temperature and Pressure

10.5. CO2 Injection During Carbon Capture and Storage or CO2-EOR

Conclusions

Appendix A. Fundamentals of Mathematics for ACROSS Processing

Appendix B. ACROSS Source Details

Appendix C. Processing of Acquired Data

References

Index

Copyright

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Preface

In recent years oil and gas industries entered a new stage called unconventional natural resources. The unconventional natural resources are heavy oil reservoirs such as oil sands and shale oil, shale gas, deep-sea oil and gas fields, coal-bed methane, and oil and gas in sub-basalts. The methane hydrate will be an unconventional natural resource in the future. To produce heavy oil efficiently, enhanced oil recovery (EOR) technology has been used. In EOR, vapor or supercritical CO2 is injected to the heavy oil layer to increase the mobility of heavy oil by softening and decreasing viscosity. During injections, it is better to monitor the physical state of the reservoir by seismic methods in addition to reservoir engineering technologies using history matching. The monitoring of physical state changes in EOR is called time-lapse technology. Carbon capture and storage (CCS) uses the same technology as CO2-EOR.

The time-lapse monitoring during EOR has been done by various methods: repeated 3D seismic surveys called 4D seismic survey, well loggings, distributed acoustic sensor, well-to-well seismic or resistivity tomographies, vertical seismic profile, interferometry synthetic aperture radar, distributed temperature sensor at borehole and/or surface, passive seismic method to monitor earthquakes, seismic interferometry, and Accurately Controlled and Routinely Operated Signal System (ACROSS) seismic method.

The permanent reservoir monitoring is one of the time-lapse technologies. This technique has been extensively used in the North Sea region, off Azerbaijan, and off Brazil by using ocean bottom cable, or ocean bottom seismograph laid down at the ocean floor. In these fields the monitoring of existing reservoirs has been carried out to enhance the efficiency of oil recovery. The shootings from the ocean surface have been repeated to learn the physical states of oil fields. Time lapse can tell the temporal change of oil reservoirs.

During shale gas production, passive seismology technique is used to monitor the fracking quakes. The 4D seismic and other methods are not commonly used because the average life of each well in shale gas production is short, and these measurements raise the production costs. If the monitoring costs becomes cheaper, the time-lapse technology can be used in shale gas production.

In this book, a new ACROSS time-lapse technology is introduced. This method is relatively new for the geophysical exploration tools. ACROSS is based on signal-processing strategy developed by Dr. Kumazawa and his colleagues since 1994 just before the 1995 Great Hanshin earthquake (Mw  =  6.9) in Kobe, Japan, and it has been applied to seismic measurements and electromagnetic measurements. He intended to use this technology for the continuous monitoring of earthquake nucleation processes along the plate subduction boundaries. The authors have spent their efforts applying this technology to the time-lapse approach for oil and gas exploration and CCS.

The ACROSS seismic source is comprised of motor and eccentric weight. By the rotation of an eccentric weight by a motor, the centrifugal force is generated. The instantaneous position of weight mass is controlled in reference to the very accurate GPS time standard. The ACROSS seismic source uses a similar frequency sweep method as one used in conventional vibrators, except for the concept of constant repetition. For example, the sweep from f1 to f2 during the repetition time frame of Tm generates a set of line spectrum from f1 to f2 with the frequency spacing of 1/Tm. Because the line spectra of source signature are precisely obtained, the enhancement of signal-to-noise ratio (S/N) could be achieved by stacking of plural sets of sweeps in time domain or frequency domain. If the source signature does not change during several days, you can stack the data during several days. One of the ACROSS seismic sources can generate 3.9×10⁵ N at 50  Hz comparable to the large land vibrator, but stacking the long data can give much higher S/N over 10–50  Hz than ordinary seismic vibrator source.

The repeatability of time lapse is the most important factor. By mounting the ACROSS seismic source on the heavy concrete base, we can obtain high repeatability even if sources and geophones are at the surface. By use of buried geophones at a few tens of meters, much better repeatability can be achieved.

Other characteristics are simultaneous generation of vertical and horizontal forces in the case of the horizontal rotational axis. The addition of received signals from clockwise and counterclockwise rotations gives the vertical force response, and the subtraction of two received records from both rotations gives the horizontal force response. The P- and S-waves are dominant in the former and latter processed records, respectively. The simultaneous excitations of vertical and horizontal vibrations cannot be achieved by conventional seismic sources.

Another uniqueness of the ACROSS seismic source is the separation of background noises and source signals. If the fracking quakes in shale gas production are included in background noises, you can separate fracking quakes from active seismic signals. By this technique, the active and passive simultaneous time-lapse methods can be obtained. If the noises come from traffic noise, human activities, and natural noises generated by weather changes, the cross-correlation of separated noise components between two locations gives seismic interferometry, which gives Green's functions between two locations, and the monitoring of seismic interferometry can be used for the time-lapse study.

Because the ACROSS seismic source is placed to solid base minimizing the temporal change of source signature to obtain good repeatability, it is difficult to get dense source spacing. In order to make sure to obtain reasonably good imaging by a few fixed-source locations, simulations for this circumstance and field tests have been carried out. The several simulations using reverse-time technique gave good images of temporary changing zones even if only one seismic source and array of geophones was used. The field test was carried out by air injection to subsurface, and the migration of air in the subsurface was imaged time to time. Currently the ACROSS technology has been tested in Aquistore, Saskatchewan, Canada, in CO2-EOR experiment.

This book summarizes the time-lapse studies in the world and describes the technology of ACROSS time lapse with the principle of ACROSS methodology and unique processing methods.

We hope that this book helps you understand the new ACROSS technology and that you will apply the ACROSS time-lapse technology to oil and gas and CCS explorations.

Acknowledgments

The Accurately Controlled and Routinely Operated Signal System (ACROSS) technologies have been developed in the Tono Geoscience Center of the Japan Atomic Energy Agency by Drs. M. Kumazawa, T. Kunitomo, T. Nakajima, K. Tsuruga, H. Nagao, and Y. Yokoyama and in Nagoya University by Drs. K. Yamaoka, T. Watanabe, and R. Ikuta. Dr. N. Fujii helped them though aggressive discussion. The authors express our great thanks to them for their continuous effort to develop the ACROSS methodology. Dr. T. Kunitomo gave us a great deal of advice for manufacturing and operating ACROSS seismic source. He made the hardware and software designs of ACROSS seismic source.

We also express our great thanks to JCCP (Japan Cooperation Center Petroleum) and officers of JCCP for their financial support and their aggressive support of our studies and field surveys in Saudi Arabia. We express our great thanks to many colleges in Saudi Arabia and Japan, including Dr. K. Al-Damegh; Messrs. G. Al-Aenezi, K. AlYousef, O. Lafouza, F. Almalki, A. Alhumaizi, I. Alrougy, M. S. Alajmi, I. Ajurayed (KACST); Drs. R. Kubota, K. Murase, A. Kamimura, and Messrs. O. Fujimoto, H. Ohmura, E. Nishiyama, Y. Kanai, O. Tazawa, G. Kato, T. Hasegawa, H. Fukatsu, and Ms. Y. Mori (Kawasaki Geological Engineering Co. Ltd.), and Mr. S. Ito, Dr. A. Guidi, Messrs. M. Takano, and T. Fujiwara (NTT data CCS Co. Ltd.) for their great efforts on fieldwork and data processing. Without their great efforts, we could not have obtained the present results.

Mr. K. Ino of Sanko Keisoku Service Co. Ltd. and engineers in Tomei-Koki Co. Ltd. manufactured ACROSS seismic source and gave useful advice about its operation.

We express our great thanks to Ms. Tasha Frank, Marisa LaFleur, Amy M. Shapiro, Maria Bernard, and Mr. J. Fedor for encouraging us to publish this work and assisting our writing.

Finally, our thanks go to Ms. K. Sekiguchi who helped with the final stage of writing.

Chapter 1

What is Time Lapse?

Abstract

This chapter describes the scope of this book. The terminology of time lapse is explained. 4D seismic method is widely used for the time-lapse study. As an alternative time-lapse method, the