Study of hydrogen sulfide effect on acrylonitrile butadiene rubber/hydrogenated acrylonitrile butadiene rubber for sealing application in oil and gas industry

Abstract

Acrylonitrile Butadiene Rubber (NBR) and Hydrogenated Acrylonitrile Butadiene Rubber (HNBR) have been widely used in many sealing applications for downhole operation. To build practical operation limits for NBR and HNBR packer elements, it is required to fill the gap between laboratory‐scale tests and field operation experience on how packer elements behave in such conditions. This study encompassed the experimental work on NBR and HNBR packer elements exposed to various sour conditions comparable to field operation. The elastomer specimens, such as NBR, showed less resistant to H2S in the controlled laboratory tests (e.g., at 121°C and 52.5 MPa with 5% of H2S) compared with an uncontrolled environment inside oil and gas well (e.g., at 134°C and 47 MPa with 3.5% of H2S). The behavior could be explained by different exposure conditions like exposure geometry, stress, temperature, pressure, and H2S concentrations. This is potentially the first‐ever comprehensive study in the oil and gas industry, which shows that the operation limit of NBR and HNBR packer elements can be extended to a higher H2S concentration.

New methodology to predict operational limit of hydrogenated acrylonitrile butadiene rubber packer element for downhole application in energy industry

“…The new findings extended our previous works 14,15 to more complex geometry and compression of HNBR downhole packer using fundamental material behavior such as viscoelasticity, hyperelasticity, chemical degradation based on laboratory tests, and FEA for long-term sealing application. The current study has additional consideration of fluid aging for a long-term operation to conventional FEA analysis of packer rubber studied by Zheng et al 16,17 and Chen et al 18 The proposed FEA methodology by chemical aging is not limited to the size of the elastomer shape and can be readily extended to develop a successful operation limit for various elastomer applications in the energy industry.…”

“…At the same time, a broad peak within 3200–3400 cm −1 appears for the center and the surface of the aged elastomer. The peak can be assigned to the presence of OH and NH 2 groups in the specimen and hence the formation of amide groups due to the chemical degradation 13,14 . The analysis of the peak intensities in Figure 9b, reveals that surface is the most aged location.…”

“…The peak can be assigned to the presence of OH and NH 2 groups in the specimen and hence the formation of amide groups due to the chemical degradation. 13,14 The analysis of the peak intensities in Figure 9b, reveals that surface is the most aged location. Hence it is believed that chemical degradation is a diffusion-controlled process.…”

“…The previous work 14,15 was extended to more complex geometry and compression of HNBR downhole packer using fundamental material behavior such as viscoelasticity, hyperelasticity, chemical/physical degradation based on laboratory tests, and FEA for long-term sealing application (i.e., a completion downhole application). Thereafter, the proposed methodology was used to develop an operational limit of the downhole packer in completion brine, calcium bromide (CaBr 2 ).…”

“…Previous work 14 reported a practical operational limit for an NBR/HNBR packer element based on the comparative study between laboratory‐scale tests and field operational experience on how packer elements behave in such conditions. The elastomer specimens, such as NBR, showed less resistance to H 2 S in the controlled laboratory tests compared with an uncontrolled environment inside an oil and gas well.…”