APPARENT POROSITY AND PERMEABILITY MODEL OF INORGANIC MATTER WITH WATER FILM IN SHALE GAS RESERVOIRS

Shale gas reservoirs have low original water saturation, mostly as irreducible water. Based on the microscopic forces between the liquid and solid surfaces, this paper presents a method for calculating the thickness of water films in different inorganic pores in shale. The water film distribution at different water saturations in the inorganic matter is obtained, considering the multi-shaped pores in inorganic matter. Using the calculated water film distribution, the gas storage and transport capacity at different water saturations are studied, considering gas migration mechanisms in microscale pores and the characteristics of inorganic matter. Models for the apparent porosity and permeability model of inorganic matter with water film are proposed. The effects of water saturation on apparent porosity and permeability of inorganic matter were analyzed. The results showed that with an increase in water saturation, apparent porosity decreases greatly. The gas storage of reservoirs in which the water saturation is 0.20 is about 25% lower than that without water film. When the water saturation increased from 0 to 0.20, the apparent permeability decreased by about 40%.

Automated summary

This paper investigates the impact of water saturation on gas storage and transport capacity in shale gas reservoirs by calculating water film thickness in different inorganic pores. Models for apparent porosity and permeability of inorganic matter with water film are proposed, and the effects of water saturation on these parameters are analyzed. Results show that increasing water saturation significantly reduces apparent porosity and permeability, leading to lower gas storage and transport capacity in reservoirs.