Reconsideration of the Adsorption/Desorption Characteristics with the Influences of Water in Unconventional Gas Systems

Table 3

Comparison of the essential differences between physical adsorption and physical desorption.

Characteristics	Physical adsorption	Physical desorption
The process of action	Coupled to the thermal evolution of hydrocarbon generation and expulsion process (spontaneously)	Drainage-depressurization-desorption (passively)
Time	Long term (millions of years)	Quiet short (days or hours)
Types	Physical adsorption and chemisorption	Physical adsorption (including depressurized desorption, dispersed desorption, displacement desorption, and temperature rise desorption)
Conditions	Dehydration, rise of temperature, and pressurization during the formation of gas reservoirs	Limited pressure drop, restricted matrix pores, and permanent temperature
Influence factor	Adsorptive capacity of gas-bearing organic matters, pressure, temperature, and moisture content	Dispersion speed of free-state gas, etc.