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by Thomas Webster on Wed, Sep 21, 2022 @ 08:09 AM
With 80% of Alberta’s oil sands buried 150 meters to 450 meters deep on average, steam-assisted gravity drainage (SAGD) is the trusted method for heavy crude oil and bitumen recovery. High-temperature steam is injected into the oil sands through the injection well to lower the viscosity of the bitumen. The heavy oil is then recovered from the production well. In addition to the heavy oil, SAGD also recovers water—90% of which is recycled back into the system.
Often times this recovered water contains dissolved solids, which in high concentration, can damage the system. While most of them are recycled, the organic compounds and solids remain as residue—the “blowdown.” The cost associated with replacing the lost water can be very high, decreasing the overall cost-efficiency of the project. Its impact on the environment can be another hindrance.
A smart way to optimize the cost of production is to use a sampling system that can analyze the quality of the treated water.
SAGD Blowdown and the Need for Sampling
SAGD projects can be costly given their intense energy requirement, and the cost associated with production and refinement. Therefore, water acts as a counteraction because it’s easily available, economic, and can be recycled. When water is converted into steam and fed into the subsurface to extract heavy oil, the water retrieved can be contaminated with many organic compounds and dissolved solids.
As the water is recycled in the boiler, some amount may be discarded to avoid the high concentration of suspended solids. This is because the solids can result in contamination and damage within the boiler. This discarded amount of water is the blowdown which helps to prevent accumulation of the contaminants. However, the major issue with blowdown is that:
- A high blowdown rate is ideal to prevent impurities from concentrating and affecting the recovery process.
- A high blowdown also significantly increases the cost of the project due to the additional cost for:
- Makeup water
- Waste disposal
- Water treatment plant capacity
The makeup water is the amount of water required to replace the water lost during the blowdown. An effective way to minimize the SAGD blowdown rate is through the use of a sampling system.
How Does Sampling System Help?
Pictured: Carbon steel tube-in-tube coils used to sample steam off of boilers.
The downside of a high concentration of impurities in the recycled water is that they can cause issues like corrosion, fouling, and scaling in the boiler. A sampling system will allow you to analyze and treat the water used in the SAGD recovery process, producing high-quality steam.
The sampling system will grab the sample of the treated water to identify its chemical characteristics and composition. This process can effectively indicate the presence of contamination and any potential fluid that may cause defects in the processing system. However, when collecting this sample it is important to consider the following factors that may affect the overall analysis:
- The pressure and temperature requirements
- Phase changes of the fluid
- The concentration of impurities which may vary at different points of the container/pipes
- Leaks or contamination in the system
A reliable sampling system will ensure true sample representativeness by making the use of specialized sampling cylinders, continuous flow systems, and sample heating/cooling systems. By analyzing the samples, the system can:
- Verify the process conditions
- Monitor water quality
- Identify the quality of the final product and its adherence to the desired specification
- Monitor environmental emissions
Leverage a Swagelok Sampling System to Reduce Production Costs From SAGD Blowdown
At Edmonton Valve & Fitting, we understand that the cost and productivity of your SAGD project are of prime importance. With our Field Advisory Services, we can perform sampling audits to identify the discrepancies in your grab and continuous sampling system and make recommendations on how to mitigate them. This is supported through grab sampling cylinders and tube-in-tube systems solutions. By understanding the processing requirement of your water samples, you can optimize the cost of your SAGD production.
To discuss the specific needs of blowdown management for your fluid system, contact Edmonton Valve & Fitting, your local fluid system expert, today. Or you can get started by downloading the Grab Sampling Systems Application Guide.