ABSTRACT:

Water swellable materials have many applications in our every day lives. Applications ranging from construction to pharmaceuticals have been introduced with more coming out in greater number. One of these newer uses has been to help activate a packer seal in a downhole environment. It is not a new idea to use swelling polymers for down-hole applications but it certainly has been a challenge. Sealing with self-energizing and low cost materials is attractive, but with High Temperature High Pressure (HTHP) and harsh chemical environments, many materials have been eliminated for downhole use. In this water swelling study, acrlyonitrile butadiene polymer (NBR) was chosen to be the base material because at certain temperatures and pressures, NBR is a very cost effective downhole sealing material. Different swelling agents and super water absorbent materials were mixed into the rubber compounds to evaluate swell behaviour. Materials having functional groups with a similar polarity to acrylonitrile were selected and compounded into test formulations for this study. Since the main mechanism for swelling is osmotic pressure, polymers and salts were chosen so that they met the criteria for polarity as well as maximizing the osmotic pressure effect. The effects of temperature and pressure were studied for different swelling salt concentrations on swell rate. Swell tests for these compounds were also performed at different temperatures, in fresh and salt water, with and without pressure. In this study, simple, low molecular weight carboxylic acid salts showed about 200% weight and volume change after days of exposure to test conditions. Compared to the more conventional super absorbent polymers, these organic acid salts yielded a slower and more controllable swell rate without significant loss in Durometer hardness. By retaining their hardness, these elastomers were better able to maintain sealing integrity under working conditions

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