A review of the shale wellbore stability mechanism based on mechanical-chemical coupling theories

Abstract

Wellbore instability in hard brittle shale is a critical topic related to the effective exploitation of shale gas resources. This review first introduces the physical-chemical coupling theories applied in shale wellbore stability research, including total water absorption method, equivalent pore pressure method, elasticity incremental method of total water potential and non-equilibrium thermodynamic method. Second, the influences of water activity, membrane efficiency, clay content and drilling fluid on shale wellbore instability are summarized. Results demonstrate that shale and drilling fluid interactions can be the critical factors affecting shale wellbore stability. The effects of thermodynamics and electrochemistry may also be considered in the future, especially the microscopic reaction of shale and drilling fluid interactions. An example of this reaction is the chemical reaction between shale components and drilling fluid.

Keywords

Petroleum engineering / Shale / Wellbore stability / Mechanical-chemical coupling / Instability mechanism

Acknowledgments

The financial support obtained from the National Natural Science foundation of China (Grant Nos. 51474185 and 41302123), the National Key Basic Research and Development Program, the (973 Program) China (Grant No. 2013CB228003), the China Postdoctoral Science foundation (Grant No. 2014M560728), and the Young Scholars Development Fund of SWPU (Grant No. 201231010031) is appreciated.

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