Natural gas is a kind of efficient, economic, and clean energy. With the rapid development of our economies, the demand for natural gas is climbing year by year. With the development and advancement of exploration technology, the world’s largest volcanic gas reservoirs were discovered in China. As an important part of natural gas resources in China, the discovered resources in volcanic gas reservoirs reach up to several trillion cubic meters, the proved gas in place is up to several hundred billion cubic meters, and the production keeps growing annually. The exploration and development of natural gas in China is in a period of vigorous development. As a new domain, the rational development of volcanic gas reservoirs plays a more and more important role in the natural gas industry.

Compared with conventional sandstone or carbonate gas reservoirs, the geological conditions of volcanic gas reservoirs are much more complicated, and their exploitation is difficult. Volcanic reservoirs, formed after multistage volcanic eruption, are composed of multilevel, superimposed, complex internal structural units with various rock types; their lithology and lithofacies are complex and change laterally. It is difficult to identify and predict effective reservoirs because of the complex mechanism of reservoir genesis; the distribution of pores, cavities, and fractures; and the great change in reservoir thickness and physical properties. The complexity of geological conditions results in diverse gas-water distributions, complex porous-flow mechanisms and development characteristics, big differences in productivity, and great difficulty in rational development. Meanwhile, there are few worldwide development examples of volcanic gas reservoirs, and this implies a low degree of research, no successful experience, and a lack of mature theoretical and technological bases. It is a world-class puzzle. In order to realize the rational development of volcanic gas reservoirs, the top priority is to understand volcanic gas reservoirs. Volcanic gas reservoir characterization is the key to solve the problem. Therefore, it is imperative to do more research on volcanic gas reservoir characterization, as this is an important riddle to solve.

In recent years, the authors participated in scientific research and production practice for volcanic gas reservoir development in the Songliao basin and the Junggar basin, such as the research that focused on basic theories, key technologies, development plan design, and production performance tracking. Particularly in volcanic gas reservoir characterization, through the application of numerous data from field outcrops, laboratory experiments, and field production, we innovatively developed characterization methods and related technologies with independent intellectual property rights. Accordingly, we obtained much more knowledge of volcanic reservoirs, guided the rational development successfully, and accumulated abundant practical experiences.

Because hydrocarbon reserves and production of volcanic reservoirs are far less than those of sedimentary reservoirs, little attention was paid to the study of these reservoirs. At present, the research thoughts and methods for sedimentary reservoirs are still applied to solve the problems of volcanic gas reservoirs, but these thoughts and methods cannot meet the actual needs of volcanic gas reservoir development. In order to fill this technology gap, the authors summarized the latest research achievements, incorporated relevant research results, and finally composed this book for reference. This book, a product of theoretical research and production practice, systematically introduces the research thoughts, methods, and technologies of volcanic gas reservoir characterization. It covers the authors’ research achievements related to volcanic gas reservoir development, including the reservoir characterization technology, development plan design, and field application examples in volcanic gas reservoirs in Daqing, Jilin, and Xinjiang.

This book is composed of 12 chapters. Chapter 1 is the Introduction, which describes the importance, technical concept, and research ideas of volcanic gas reservoir characterization. Chapters 2, 10, and 11 introduce the concept and research ideas of internal structure in volcanic gas reservoirs by systematically describing the identification and characterization of volcanic formation, volcanic edifice, volcanic massif, accumulation and permeation units, and microporous structures. Chapter 3 introduces the concepts, research ideas, identification, division, and correlation methods of volcanic stratigraphic sequences. Chapters 4, 5, 6, 8, and 9 introduce the identification and prediction technology of lithofacies, lithologies, fractures, gas-bearing layers, and water zones as well as effective reservoirs. Chapter 7 introduces the parameter interpretation technology for fractured volcanic gas reservoirs, and Chapter 12 introduces the geological model building technology of volcanic gas reservoirs.

Chapter 1 is written by Qiquan Ran, Lin Yan, and Yuanhui Sun. Chapter 2 is written by Qiquan Ran, Yuanhui Sun, and Yongjun Wang. Chapter 3 is written by Yuanhui Sun and Qiquan Ran. Chapter 4 is written by Yuanhui Sun and Qiquan Ran. Chapter 5 is written by Yongjun Wang and Lin Yan. Chapter 6 is written by Yongjun Wang and Qiquan Ran. Chapter 7 is written by Yongjun Wang and Yuanhui Sun. Chapter 8 is written by Yongjun Wang, Yuanhui Sun, and Min Tong. Chapter 9 is written by Qiquan Ran, Yongjun Wang, and Min Tong. Chapter 10 is written by Qiquan Ran and Yongjun Wang. Chapter 11 is written by Lin Yan and Yongjun Wang. Finally, Chapter 12 is written by Lin Yan and Yuanhui Sun.

Thanks for the care and help from the leaders and experts of PetroChina Research Institute of Petroleum Exploration and Development. And thanks for the support and help from the leaders and experts of the Natural Gas Department and Science & Technology Management Department of PetroChina Exploration and Production Company, and the Science & Technology Management Department of CNPC, Daqing Oilfield Company, Jilin Oilfield Company, and Xinjiang Oilfield Company. Dr. Lei Zhengdong, Dr. Zhu Liyao, and Dr. Chen Fuli and colleagues, the members of the volcanic rock project team, have done much work for this project. Professor Zhong Dakang, Professor Ouyang Yonglin, Professor Wang Pujun, and Dr. Zhang Jing and colleaguesalso contributed to this project. Professor Qiu Yinan, a famous development geologist in China, and Professor Guo Shangping, a CAS academician, gave us much help for the composition of this book. We express our sincere appreciation to them herein! The book cited or extracted some contents from the papers and literature of other researchers, so thanks to those researchers too!

At present, volcanic gas reservoir development is still in the early stage. Because of complex geological conditions and new research challenges, many problems concerning volcanic gas reservoir characterization should be solved through further research. Suggestions for improvement will be gratefully received.

The authors

November 2010 in Beijing