The Compact Separation and Compression Unit (CSU)
CSU significantly reduces cost, weight, and environmental footprint compared to conventional solutions.
The Compact Separation and Compression Unit (CSU) is a groundbreaking technology developed by Straen Energy. The system combines complex gas and liquid processes into a single compact unit, aiming to optimize separation and compression for oil, gas, and hydrogen.
Our Technology
The Principles Behind CSU Technology
CSU was developed with a focus on innovation, efficiency, and safety. The technology introduces solutions that address the challenges of traditional compression systems while providing significant benefits in terms of energy efficiency, space savings, and operational safety. Key principles include:
Efficient isothermal compression
CSU achieves near-isothermal compression using an innovative water-spray technology that reduces heat buildup during compression. This increases efficiency and reduces energy consumption.
Compact and flexible design
CSU is designed to eliminate the need for multi-stage compressor systems with intercoolers and scrubbers. This results in a more compact solution that is easier to integrate into both new and existing installations.
Safety first
CSU uses water for sealing and compression, eliminating the risk of dynamic leaks in gas service and making the system ideal for handling high-pressure hydrogen.
Revision 1
Revision 1 – Basic Concept Development (2017)
30 bar wellhead pressure,compact separation and compression using CCVs
The CSU system operates as a series of compact cylindrical separators (CCVs) that handle gas, oil, and water from the wellstream in an efficient and controlled process. Each CCV has a volume of 5 m³ and functions in a cyclic sequence, where filling, compression, and emptying are performed in a logical order. This enables continuous and stable operation.
Operational sequences
Filling the CCV
The wellstream—consisting of gas, oil, and water—is fed into one of the four CCVs. The gas rises naturally to the top. When the cylinder is full and the pressure is balanced with the well, both inlet and outlet valves close.
Gas compression
Water is pumped into the cylinder, gradually increasing pressure on the collected gas. When the gas pressure exceeds 150 bar, a check valve opens, sending the gas to a scrubber and then forward to gas lift or export.
Emptying and water reuse
Once the gas has been compressed and removed, the pressurized water—along with produced oil and water—is drained to a second-stage separator. Here, oil is separated for export, while water is reused for gas compression in the CCVs. Any excess water is pumped either to water injection or to a treatment unit prior to discharge.
The role of the ejector
Gas from the second-stage separator is led to an ejector powered by high-pressure pumped water and reinjected into the CCVs for increased utilization.
Revision 2
Revision 2 – Pilot Studies and Improved Design (2019)
Optimization of Energy Consumption
Introduction of an additional pump
A new pump was added to prevent choking at water inlet valves, eliminating system bottlenecks.
Reduced water consumption
The volume of injection water required was significantly reduced, contributing to lower energy use.
Pump division
One large injection pump was replaced with two smaller pumps, improving flexibility and efficiency.
Larger pipe dimensions
Internal piping was increased slightly in diameter to optimize liquid flow dynamics.
Revision 3
Revision 3 – Adaptation for Hydrogen and CO₂ Compression (2021)
By introducing an additional separator and a buffer tank, the operating philosophy was modified to achieve several benefits. These included cleaner gas separation using a closed-loop liquid system, which reduced erosion on pumps, valves, sensors, and instruments. Scaling and corrosion exposure were also minimized, improving safety and reducing maintenance needs.
Reduction in Energy Demand and Consumption
Changes introduced in 2021 reduced total energy demand from 1.1 MW to 0.8 MW by improving gas flow from the first-stage separator to the CCVs. There was also a slight reduction in injection water consumption, further improving overall system efficiency.
Revision 4
Revision 4 – Pilot Testing (2023)
70 bar wellhead pressure
To address challenges associated with higher wellhead pressures, a more advanced solution was developed. This included integrating a third-stage separator for oil stabilization. The modification ensures the system can handle more demanding operational conditions while maintaining effective separation and compression.
Revision 4 introduces a more complex architecture requiring more detailed planning and higher investment costs but enables greater operational flexibility and capacity. It represents a significant step toward adapting CSU technology to high wellhead pressures and more complex conditions—laying the foundation for expanded use in demanding environments.
Adaptation to Higher Wellhead Pressure and Stabilized Oil
To handle higher wellhead pressures, the design was optimized to ensure stable and safe operation under increased loads. A third-stage separator was also introduced to stabilize the oil, improving quality, readiness for refining, and producing a more efficient export oil stream.
Despite the increased complexity, the system maintains its ability to operate continuously and reliably, ensuring high efficiency even in demanding operational conditions.
Advantages and Technological Innovations
Instead of traditional mechanical compressors, high-pressure pumped water (150 bar) is used to compress the gas directly. The water also functions as a cooling medium, eliminating the need for complex cooling systems.
The system is modular, reducing both footprint and weight. This makes CSU well-suited for installation on platforms, vessels, or as subsea solutions—especially at low-pressure brownfield sites.
The entire process is monitored and controlled using logical sequencing and instrumentation that ensures precise regulation of pressures, levels, and temperatures.