Diffusion-based swelling in elastomers under low- and high-salinity brine

Abstract

Swelling elastomers are designed to swell when immersed into fluids like water, oil, or acid. The mechanism of swelling can be either diffusion or osmosis, initiating the imbibition of fluid inside the elastomer and progressively swelling it. Work presented here investigates diffusion as the swelling mechanism. Swelling experiments are conducted at two temperatures (room and 50 C) using water of different salinities (0.6% and 12%) as the swelling medium. Changes in volume, thickness, mass, and hardness are recorded. Measurements are taken before swelling and after 1, 2, 4, 7, 10, 16, 23, and 30 days of swelling. As expected, volume, thickness, and mass of the elastomer increase with increase in the number of swelling days, while hardness shows a decreasing trend. More variation is observed for all quantities in low-salinity brine as compared to high salinity, at both temperatures. However, density values are larger for high-salinity brine at both temperatures. Stokes-Einstein formula is used to determine the diffusion coefficients. Viscosity is measured using a Cannon-Fenske apparatus of size 50. Larger values of diffusion coefficient are found in low-salinity water at both temperatures, consistent with the higher amount of swelling and the faster swelling rate. These results and the diffusion-based approach will help in understanding the mechanics of swelling phenomenon. This work can aid in the development of new analytical and semi-analytical models that can predict seal pressure and other performance factors more accurately for applications in oil and gas wells.

Numerical Investigation of Elastomer Seal Performance

“…In oil wells, swelling elastomer seal is placed in the drilled hole with a certain gap between the seal and the outer casing (or formation), to ensure easy placement. With exposure to swelling fluid, the elastomer swells freely, the only driving force being dynamic swelling; through osmosis for water swellables [7], and through diffusion for oil swellables [8]. It first fills the gap between the tubular and formation; this may take a few hours to a few days depending on the elastomer type Further swelling (after filling up of the gap) generates pressure at the interface.…”

Design and construction of test facility for evaluation of swell packers in cased and open holes

“…Similar to a casing, the packer is taken down the well to the target location. These rubbers swell when they come in contact with different types of fluids and are categorized accordingly as oil-based or water-based swelling elastomers (Dorohov et al 2016;Akhtar et al 2018a). When exposed to water or crude oil, the elastomer segment swells and completes the seal, before the commencement of production (Akhtar et al 2018b).…”