Choosing Grab Sampling Systems for Sampling of Water in SAGD Operations

In SAGD processes, steam is injected downhole to heat bitumen, allowing it to flow to the surface. The steam returns to the surface as an oil/water mixture, which must be separated so the oil can be recovered and the water can be reused to generate steam. The water picks up impurities from the reservoir, including hydrocarbons, oxygen, silica, and other minerals. These impurities cause fouling, corrosion, or scaling of boiler tubes, which reduces efficiency and can eventually lead to mechanical failure.

To ensure the efficient production of high-quality steam, water must be sampled, analyzed, and treated to remove trace oil and other contaminants before it enters the boiler to be converted into steam and injected downhole again. Grab sampling provides insight into the chemistry and composition of SAGD water, letting operations know what type and dosage of treatments are needed to maintain water efficacy. However, there are special challenges in collecting representative samples in SAGD operations. It’s important to select the right grab sampling system for sampling water.

Challenges of SAGD Water Treatment and Recycling

Most boilers convert about 75-80% of water into steam. The rest is “blowdown”—a mixture of water, salts, and organic compounds. The water lost to blowdown must be replaced from another source. Higher steam quality reduces blowdown and make-up water demand, which lowers costs.

SAGD operations need to understand pH, alkalinity, water hardness, silica content, and oil content to effectively treat and reuse water. However, the high temperatures and pressures of the SAGD process present some difficulties in collecting representative samples. Pressure changes before or during sampling can cause water and other fluids to vaporize, which can cause the sample to not be representative. Because the pressure and temperature conditions must be maintained in the sample, the high-pressure, high-temperature steam also creates a safety hazard for the operators collecting it.

Grab Sampling Systems for Sampling Water

Oil, among other contaminants, must be removed from the water before it can be reused. However, online analyzers do not typically have the resolution needed to measure oil content in water, so grab sampling is preferred.

When an oil/water mixture is collected in a sample container, it begins to separate immediately. Oil can stick to the container surface, and solids settle to the bottom. To ensure a representative sample, a grab sampling system for sampling water must be able to maintain the phase and composition of the mixture. Fortunately, there are many solutions available to ensure samples are representative and can be collected safely.

There are several criteria to consider when selecting a grab sampling system for sampling water:

Pressure and Temperature Rating. Because of the high pressures and temperatures of SAGD water, the sampling system must be appropriately pressure- and temperature-rated to maintain composition and allow operators to draw samples safely. A rupture disc or relief valve is recommended for high-pressure, high-temperature fluids as a safeguard against rapid depressurization.

Sampling Container. If the fluid is not pressurized, grab samples of water can be collected in either a cylinder or a bottle. However, if the sampled water is pressurized or contains volatile impurities, a sample cylinder is required to maintain phase composition and prevent the release of vapours.

Safety. The grab sampling system must provide adequate protection for the operator and the environment. For grab sampling of water recovered from SAGD operations, this means implementing safeguards against the release of high-pressure, high-temperature vapour. A relief valve can be implemented with a cylinder collection system to safeguard against overpressure conditions from temperature changes or overfilling. Bottles should never be used to sample pressurized fluids.

Sample Representativeness. Several options are available to ensure the representativeness of grab sampling systems for the sampling of water. Surface treatments like coatings or electropolishing can reduce the absorption and adsorption of fluid into metallic surfaces, leading to a more representative sample. A purge option provides a means to remove residual contamination from the sample lines. For maximum assurance of water sample representativeness, a continuous flow system can keep water flowing through the sample system so it is always representative of the current state of the overall system.

Leverage Your Local Vendor’s Grab Sampling Expertise

Edmonton Valve & Fitting understands the challenges of grab sampling water for analysis and treatment in Alberta SAGD operations. Whether you need a new sampling system, an upgrade, or troubleshooting support, we can help. Our Field Advisors can perform an onsite evaluation to determine the best water grab sampling solution to improve reliability for your SAGD operation. They can also evaluate your existing system to identify potential problems before they occur and help you implement preventive measures to keep operations running safely and efficiently.

We make grab sampling stations to order right here in Edmonton. We'll be happy to discuss your specific needs so we can help you select the right grab sampling system for sampling water in your SAGD operation. To get started, download the Grab Sampling Systems Application Guide.