Operator finds optimal solution for steamflooding operation

There are several different methods of EOR being practiced, including steamflood and waterflood injection.

Steamflooding introduces heat to the reservoir by pumping steam into the well with a pattern similar to that of water injection. High-temperature steam heats the oil in the formation, lowering its viscosity and forcing the oil within the formation to move toward the producing well. High-temperature steam will challenge the sealing materials, which is why operators using this method of EOR can benefit from the reliability of an elastomer specifically developed for the environment.

Sealing for oil and gas applications

High-performance O-ring seals used in the oil field require specialist grades of elastomers specifically tailored to meet the challenges of the most inhospitable operating environments in the world. Sealing high-temperature steam is particularly difficult as many high-temperature elastomers are unable to maintain their sealing properties. Selection of the correct elastomer for this type of application is therefore challenging and critical.

The materials used to create seals must withstand, both physically and chemically, the extreme conditions in which they are increasingly being used. There are limited options for sealing with elastomers in hot water or steam environments in temperatures up to 288°C (550°F). Most elastomers in high-temperature steam environments will become brittle and crack, resulting in leakage from a valve, pump, or other equipment. Leakage resulting from a cracked seal can cause hazardous conditions and ultimately equipment failure and lost time.

FIGURE 1. (top) Above is a standard EPDM after 24 hours in 316°C steam. Specimen is warped with surface cracking. (Images courtesy of Precision Polymer Engineering)
FIGURE 2. This FKM terpolymer is shown after 24 hours in 316°C steam.
FIGURE 3. This FKM copolymer is shown after 24 hours in 316°C steam.

Designed to work

The seal designer has to consider many factors such as temperature range, pressure, and fluid environment in determining the optimal sealing material for an application. Temperature range of the application is an important factor that must be considered. Low temperature decreases the flexibility, and if the temperature is low enough, the material will lose its elastomeric properties. The low-temperature resistance is dependent upon the material’s glass transition temperature, or the temperature at which the elastomer changes from a rubber-like to a glass-like material.

High temperatures can increase crosslinking, where the structure of the material tightens, causing a decrease in elasticity. The material also can become chemically altered under high temperatures, where an elastomer may lose some process oils or low molecular-weight fragments of the polymer.

Pressure of the application may cause mechanical extrusion of the seal, or if gases are present they will absorb into the elastomer, creating the potential for damage from rapid gas decompression. Permeation of a gas under high pressure may not result in any long-term effect providing the pressure is released gradually, allowing the gas to permeate out of the elastomer slowly.

The fluid environment is critically important to seal selection. Fluid incompatibility can cause high-volume swell in the seal. Though the volume increase in such instances may be reversible, the effects on the polymer may not be.

In the case of hot water and steam, all three factors need to be considered: high temperature that can affect elasticity and sealing force, water that can swell or react with the polymer, and pressure that can extrude low-strength materials or increase the risk of rapid gas decompression.

The limitations of the most common sealing materials create an opportunity for new elastomers that will seal in applications such as geothermal wells, turbines, EOR, and other situations where high-temperature steam may be encountered. In each of these applications, reliability is critical for safety as well as profitability. High-temperature steam and water-resistant seals enable downhole tools to be used to improve well drilling and completion.

Standard materials

Standard ethylene propylene diene monomer (EPDM) elastomers are well suited for water-sealing applications. They seal up to approximately 150°C (302°F) but will show property loss such as high-volume swell, durometer loss, and cracking in higher temperature steam applications (Figure 1). If this seal was used in a valve or other application, there would likely be a leak or failure requiring downtime and repair.

Fluoroelastomers (FKMs) are well known for their resistance to high, dry temperatures. They will typically retain properties up to 200°C (392°F). In high-temperature steam, FKMs become brittle and crack, which can result in seal failure (Figures 2 and 3).

Nitrile butadiene rubber and hydrogenated nitrile (HNBR) elastomers also become brittle after high-temperature steam exposure.

What works in HP/HT

Recently an upstream EOR application managed by a global E&P company was experiencing failure of a standard FKM elastomer in an HP/HT steam environment. Work had halted, and operating costs were rising. The operator required a solution immediately.

Precision Polymer Engineering (PPE) offered a new EPDM elastomer, EnDura E90SR, which is resistant to both hot water and saturated steam – the type of solution the operator was seeking.

FIGURE 4. This EnDura E90SR O-ring remains flexible without cracking after 24 hours in 316°C steam.
FIGURE 5. Bottom left: a fresh O-ring seal; Bottom right: A steam-aged EnDura E90SR O-ring seal left in 288°C for 168 hours.

The material is in the 90 durometer range, making it resistant to extrusion at elevated temperatures and rapid gas decompression. Tests have shown that E90SR retains its properties in very high-temperature steam at both 288°C and 316°C (600°F) and has resistance to rapid gas decompression (Figures 4 and 5).
PPE’s rapid response reduced downtime by two weeks, minimizing the daily accruing costs. The PPE materials supported the EOR operation and survived the HP/HT environment, unlike materials used before.

EnDura E90SR helps to improve the performance of products in geothermal tools, pumps, valves, turbines, and other components that require a critical seal in higher temperature-saturated steam environments. Its use also can extend equipment life, mitigate costly downtime or repairs, and enable seal designers to use elastomer seals in environments that are likely to degrade nearly all other commercially available elastomers. Engineers now have more choices in designs and the range in which they can operate their equipment.