Program > Keynote Speakers > Dongxiao Zhang

Carbon Dioxide Fracturing for Tight/Shale Gas Reservoirs
Dongxiao Zhang, Peking University, China
Biosketch

DONGXIAO “Don” ZHANG

Professor Zhang is the Dean of College of Engineering, Director of Institute of Ocean Research, and Director of Institute of Clean Energy at Peking University, Beijing, China. He had held positions as Senior Scientist at Los Alamos National Laboratory, Miller Chair Professor at the Department of Petroleum and Geological Engineering at the University of Oklahoma, and Chair Professor at the University of Southern California. He has authored 2 books and published over 160 peer-reviewed papers. He earned both his Master’s degree and Ph.D. in hydrology and water resources in 1992 and 1993, respectively, from the University of Arizona. Professor Zhang is an internationally well known expert in unconventional oil and gas production, groundwater hydrology, and geological carbon sequestration, whose research achievements in stochastic modeling, numerical simulation, and inverse modeling are widely adopted by his peers.

Professor Zhang has been an associate editor for SPE Journal, Water Resource Research, Advances in Water Resources, SIAM Multiscale Modeling and Simulation, Journal of Computational Geosciences, and Vadose Zone Journal. He has served as a panelist on the RCUK Review of Energy, UK Research Councils, a member of US National Research Council’s Committee on New Research Opportunities in the Earth Sciences, a council member of World Economic Forum Global Agenda Council on New Energy Architecture, and an elected member of board of trustees at Western Academy of Beijing. Professor Zhang is an Honorary Member of Society of Petroleum Engineers, a Fellow of Geological Society of America, and a Member of the U.S. National Academy of Engineering.

http://en.coe.pku.edu.cn/Faculty-by-Dept/74.htm

Abstract

Massive hydraulic fracturing requires an enormous consumption of water and introduces many potential environmental issues. In addition, water-based fluid tends to be trapped in formations, reducing gas phase relative permeability, and causes clay mineral swelling, lowering absolute permeability. Carbon dioxide (CO2) is seen as a promising alternative working fluid that poses no formation-damage risk, is free of detrimental environmental effects, absorbs onto matrix to permanently fix greenhouse gas as well as to enhance tight/shale gas production, and is capable of stimulating more complex and extensive fracture networks. However, very few if any extant research has quantitatively analysed the effectiveness of CO2-fracturing, except for some qualitative fracturing experiments based on acoustic emissions. In this study, we systematically examine water- and CO2-fracturing, and compare their performance on the basis of a rigorously coupled geomechanics and fluid-heat flow model. Investigated are how fluid viscosity, compressibility, in-situ stress, and rock permeability impact breakdown pressure and leak-off, as well as fracturing effectiveness. It is found that: (1) CO2 has the potential to lower breakdown pressure, benefiting fractures’ propagation; (2) water-fracturing tends to create wider and longer tensile fractures compared to CO2-fracturing, so as to facilitate proppant transport and placement; (3) CO2-fracturing could drastically enhance the complexity of artificial fracture networks even under high stress anisotropy conditions; (4) thickened-CO2 tends to generate simpler fracture networks than does supercrtical-CO2 (SC-CO2), but still more complex than does fresh water; and (5) the alternating fracturing scheme (i.e., SC-CO2 fracturing followed by thickened-CO2 fracturing) can readily create complex fracture networks, as well as carry proppant to keep artificial fractures open. This study reveals that, for intact reservoirs, water-based fracturing can achieve better fracturing performance than CO2-fracturing; however, for naturally fractured reservoirs, CO2 fracturing can constitute an effective way to stimulate tight/shale gas reservoirs, improving gas production.