Experimental study on hydration damage of anisotropic shale under high temperature

Abstract

The Longmaxi shale samples are used to investigate the anisotropic hydration damage characteristics of shale under high temperature conditions. The FEI Qemscan 650F energy dispersive spectroscopy (EDS)-field emission scanning electron microscope (FESEM) is used to help observe the evolution characteristics of shale clay mineral and micro-structure under different temperature, pressure and soaking time conditions from beddings vertical and parallel directions. It comes to the conclusion that the hydration characteristic induced by microscale anisotropy of Longmaxi shale varies a lot. The damage behavior in the bedding-parallel plane is characterized by dilatation-closure-collapse process of primary fractures which exists in a large amount of nano-scale and micro-scale corrosion pores. While the damage behavior in the bedding-vertical plane is mainly represented as a mass of nano-scale and micro-scale corrosion pores. It’s also found that the shale hydration damage is faster under higher temperature condition when the soaking time and pressure are the same. Besides, under the same temperature and pressure conditions, the shale microstructure hydration process trends to increase at the beginning and be flat at last. The higher temperature shorten the time spending on shale hydration and its inner relationship is required more experiments.