High Temperature Elastomers in Oil & Gas

By December 21, 2017articles, News

Elastomers are used all over the Oil & Gas industry. They facilitate downhole packers sealing, they allow progressing cavity pumps (PCP) to work, and they provide sealing materials for valves and equipment on the surface.

Frequently the root cause of a failure is that an inappropriate elastomer was selected (or defaulted). The elastomer choices seem like such a minor element of a ball valve specification that operators will simply take the default material.

The default Nitrile rubber (also known by such names as Buna-n, perbunan, acrylonitrile butadiene rubber, and NBR) is often a very reasonable choice in lower temperatures, mild fluids, and service not subject to Rapid Gas Depressurization.

When conditions are suitable, it can be a very effective and cost-effective choice. When conditions are not suitable it can be a disastrous choice.

Deep offshore and unconventional wells are forcing consideration of high temperatures, difficult chemicals, and high pressures. All of these issues require a careful evaluation of materials choices in the equipment selected. Picking a low-temperature elastomer for the stator in a progressing cavity pump located in the Barnett Shale would result in run times measured in “revolutions” instead of days or weeks. Not considering winter in selecting materials for surface equipment on the Alaska North Slope or the shale fields of Northern British Columbia could easily end in disaster. The most sensitive element tends to be the elastomers used in sealing surfaces.

The basic building block of all plastics is the “monomer”. Monomers are complex structures of carbon compounds that have the ability to bond with other monomers (both of the same species and to a limited extent to other species) to make “polymers”. Materials are called “plastic” if all of the polymer chains are similar to each other and each strand is distinct from other strands.

When the polymers “cross link” the plastic becomes an elastomer. Cross linking was first done by Charles Goodyear (1839) when he “vulcanized” natural rubber (NR) by adding sulfur to improve the performance of rubber products. When polymers cross-link, their structure resembles a fishnet more than a rope and there is room for the bulk structure to flex without breaking.

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