Stress damage of shale during the uniaxial loading process will cause the change of permeability. The study of stress sensitivity of shale has focused on the influence of confining pressure on shale permeability and the change of shale permeability during the loading process of axial stress is lacking. The permeability of gas shale during loading process was tested. The results show that shale damage macroscopically reflects the process of axial micro-cracks generation and expansion, and the axial micro-cracks will cause permeability change during the loading process. There is a good corresponding relationship between damage development and micro-crack expansion during the process of shale loading. The damage factor will increase in the linear elastic stage and enlarge rapidly after entering the stage of unstable micro-crack expansion, and the permeability of shale increases with the increasing of shale damage. The research results provide a reliable test basis for further analysis of the borehole instability and hydraulic fracture mechanisms in shale gas reservoirs.

In the process of well completion with mechanical screen to control sand, once the water content of the reservoir increased, the montmorillonite in clay minerals would swell which combined with formation sand has an obvious effect on the plugging of screen pipe in production string. According to the prediction of water production of reservoir, shale expansion instrument was used to establish the relationship between the different water content and swelling properties of montmorillonites and combined with the clogging test of screen under different water content to evaluate the blocking effect of montmorillonite under different water content on the clogging of screen in the process of sand control. It can be found in the experiment that: (1) If the reservoir products water, the expansion height of two kinds of montmorillonites is similar when the water content of oil is less than 10% or more than 20%, the expansion height of montmorillonites is large of which expansion rate can reach to 188% when the water content is between 10 and 20%. (2) Through the simulation experiment of sand control, when the water content is 10 and 30%, the screen blocking is the fastest, and the productivity index per meter is the lowest, the blockage rate is increased by nearly three times when the water content of oil is 0. (3) The influence of concentration ratio of oil and water on the productivity index per meter of metal mesh screen is larger than the swelling of montmorillonites which is mainly reflected in the water content is close to 20–30%. The degree and speed of screen blocking can be reduced by reducing the water content of produced fluid.