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The Scientific World Journal
Volume 2013, Article ID 720271, 9 pages
Research Article

Wellbore Stability in Oil and Gas Drilling with Chemical-Mechanical Coupling

1State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China
2Department of Petroleum Engineering, China University of Petroleum, Beijing 102249, China

Received 28 April 2013; Accepted 18 June 2013

Academic Editors: K. Kabiri, A. Vorontsov, and Y.-M. Wu

Copyright © 2013 Chuanliang Yan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Wellbore instability in oil and gas drilling is resulted from both mechanical and chemical factors. Hydration is produced in shale formation owing to the influence of the chemical property of drilling fluid. A new experimental method to measure diffusion coefficient of shale hydration is given, and the calculation method of experimental results is introduced. The diffusion coefficient of shale hydration is measured with the downhole temperature and pressure condition, then the penetration migrate law of drilling fluid filtrate around the wellbore is calculated. Furthermore, the changing rules of shale mechanical properties affected by hydration and water absorption are studied through experiments. The relationships between shale mechanical parameters and the water content are established. The wellbore stability model chemical-mechanical coupling is obtained based on the experimental results. Under the action of drilling fluid, hydration makes the shale formation softened and produced the swelling strain after drilling. This will lead to the collapse pressure increases after drilling. The study results provide a reference for studying hydration collapse period of shale.