Investigation of the controlling rock petrophysical factors on water phase trapping damage in tight gas reservoirs

Abstract This paper presents an investigation into the effect of rock physical parameters on water phase trapping (WPT) damage in tight gas reservoirs. The investigation involved water imbibition and drainage experiments that were performed to simulate the WPT formation process. Gas permeability was measured before and after WPT, and an empirical formula was used to determine water film thickness in order to examine the influence of WPT on effective gas flow channel. Results showed that the average water saturation of 15 tight core samples increased from 19.41% to 44.76% during water imbibition and declined to 38.72% after drainage. Increments in water saturation caused a degree of damage to gas permeability in the 36.03%‐78.10% range with an average value of 59.31%. Comparative analysis showed that the dominant factors affecting WPT were average pore throat radius followed by rock permeability and porosity. Meanwhile, calculations showed that water film thickness in the 21.22‐38.18 nm range correlated to a reduced effective gas flow channel of 20.20‐45.15 nm caused by WPT, which suggests that tight rocks with smaller pore throats may be particularly sensitive to WPT damage. The relative size of the water film filling the pore throat, trapping gas, and reducing the effective gas flow channel together with the size of the pore throat itself were found to be the most common damage mechanisms of WPT and have proven to be fundamentally beneficial in understanding the controlling factors of these damage mechanisms.