Abstract: The movability of coalbed water in deep coal reservoirs is a key factor restricting the effective output of coalbed methane. Based on the full investigation of results of previous researchers, combined with theoretical analyses and experimental test results, in order to clarify the evaluation method of the movability of coalbed water in deep coal reservoirs, this study discusses the progress of the research on the dynamic mechanism of the movability of coalbed water in deep coal reservoirs, analyzes the influencing factors and laws of the movability of coalbed water, and points out the development direction of future research. The results show that: A combination of methods is needed to characterize the water occurrence state and the water movability in coal reservoirs. Water vapor isothermal adsorption experiment can be used to clarify the water adsorption characteristics of nanoscale pores, and it is recommended to prioritize the use of nuclear magnetic resonance and mercury injection experiments to jointly characterize the movable water saturation and the full-scale pore structure, and then combine them with the core displacement experiment to verify the water movability in the coal reservoirs. The movability of coalbed water is affected by coal petrological characteristics, porosity and permeability characteristics, and mineral characteristics. Among them, the maximum vitrinite reflectance has a nonlinear effect on the movable water saturation by changing the coal rock pore structure, which first increases and then decreases. The movable water saturation increases significantly when the vitrinite volume fraction, ash yield, porosity, permeability and macropore (radius > 1 000 nm) volume fraction increase. While the inertinite volume fraction, fixed carbon yield, and micropore-mesopore (radius ＜ 1 000 nm) volume fraction increased to inhibit the movability of coalbed water. In the future, four research directions should be focused on, including the characterization of movable water, the main controlling factors and quantitative evaluation of water content, the simulation and mechanism analysis of water production, and the dynamic mechanism analysis of water migration in deep coal reservoirs.

Key words: deep coalbed methane, coalbed water, movability evaluation, water transport, coal reservoirs