Effects of Solvent Exposure and Oil Oxidation on HNBR Elastomer Performance in High-Temperature Inflatable Packers

Inflatable packers are extensively employed in well construction, production, and abandonment operations to achieve zonal isolation, enable precise plugging or pin-point treatments, and assist with cement placement under challenging wellbore conditions. Their reliability depends strongly on the behaviour of the elastomer sealing element when exposed to high-temperature fluids during manufacture, qualification testing and field service. This study evaluates how common processing solvents, thermally oxidised test oils, and manufacturing voids affect the performance of hydrogenated nitrile rubber (HNBR) compounds used in high-temperature inflatable packers. Laboratory conditioning was performed in methyl ethyl ketone (MEK), acetone, and heat-transfer oil (HT100) at 150 °C under controlled exposure conditions. Mechanical testing before and after exposure included tensile strength, elongation at break, tear strength, hardness and mass change. This was supported by infrared spectroscopy and microscopy to assess chemical uptake and void-related damage mechanisms. Solvent exposure caused the greatest reductions in tensile and tear strength and promoted surface cracking around near-surface voids. Fresh/new oil produced only minor changes in mechanical properties. Heating in oxidised oil caused the rubber to soften, gain mass, and stretch more easily, which agrees with the idea that the material absorbed more oil and became plasticised. Microscopic examination also showed voids formed by trapped gases during curing, typically tens to hundreds of micrometres in diameter, that served as stress concentrators and primary sites for crack initiation. Overall, the findings show that exposure to strong solvents, degraded oils, and void defects can markedly diminish the safety margin of inflatable packer elements, even when the base HNBR compound itself exhibits high intrinsic stability