A quantitative research of water distribution characteristics inside shale and clay nanopores

Abstract

Understanding the fluid distribution characteristics inside nanopores are of great significance to evaluate shale gas reservoirs. In this work, the quantitative evaluations for water saturation distribution of porous shale and clay are performed by experiments. The experimental results show that the capillary condensation is remarkable for clay pores during the process of water adsorption, the pores less than 6.76 nm would be blocked by the capillary water when the relative humidity is approximate to 0.98; moreover, the inorganic pore is hydrophilic while the organic pore is hydrophobic, the coupled effect make less water uptake inside shale sample. Meanwhile, a mathematic model for studying the effect of pore shape on water adsorption is established based on the difference of morphology characteristics between organic and inorganic pore. The results indicate that the slit pore is better similar with the actual condition, and the calculated film thickness and water saturation is more coincide with the measured value. Thus, the slit pore is more appropriate than the circular pores for studying the water uptake characteristic of shale. Our work lays the foundations for better understanding and evaluating the fluids occurrence pattern and gas generation mechanism of different pores in shale reservoir.