The following is a performance comparison of different models of compressors in casing gas recovery:
Reciprocating compressor
Pressure range: high compression ratio, single-stage pressure ratio can reach more than 10, able to adapt to a wide pressure range, from low pressure to high pressure or even ultra-high pressure, suitable for situations where the initial pressure of casing gas is low but needs to be compressed to a higher pressure
Flow range: The flow range is relatively narrow and generally suitable for gas recovery in small and medium flow casing. But by combining multiple cylinders and other methods, certain high flow demands can also be met
Stability of operation: There are many moving parts and large mechanical losses, resulting in significant vibration and noise, and poor stability of operation. Effective vibration and noise reduction measures need to be taken. However, its structure is simple, reliable, and has a long service life. Small units can operate without maintenance
Maintenance cost: The structure is complex, with many vulnerable parts such as air valves, piston rings, connecting rod bearings, etc. The maintenance cycle is short, and the maintenance workload and cost are relatively high
Energy efficiency performance: High energy consumption, but high compression efficiency. The gas compression process of a typical reciprocating piston compressor is a closed system, while the adiabatic efficiency of a large reciprocating piston compressor can reach over 80%
Adaptability: Strong tolerance to gas composition and impurities, suitable for various gases, including casing gases containing certain impurities. But the exhaust gas may carry oil stains, and for recycling processes that require high gas quality, it may be necessary to increase gas purification equipment
Screw compressor
Pressure range: The exhaust pressure generally does not exceed 3MPa, suitable for casing gas recovery in the medium and low pressure range. It has strong overpressure capability, low pulsation of exhaust pressure, no clearance volume, and high efficiency
Flow range: The flow range is wide, with a single machine capacity of over 1000kW, which can meet the gas recovery needs of medium to high flow casing
Stability of operation: Compact structure, small size, light weight, smooth operation, low vibration, low noise, low foundation requirements, can achieve no foundation operation, especially suitable for use as a mobile compressor
Maintenance cost: With fewer components and no vulnerable parts, it operates reliably and has a long lifespan. The interval between major repairs can reach 480000 hours. It is easy to operate and maintain, has a high degree of automation, and can reduce equipment operating costs. But its processing technology requirements are high, manufacturing costs are high, and the oil system is complex, requiring continuous oil supply and lubrication, making maintenance inconvenient, and the cost of replacing parts is also high
Energy efficiency performance: With frequency conversion speed regulation, it can achieve wide range stepless energy regulation, maintain high efficiency in a wide range of working conditions, and have better energy consumption performance than reciprocating compressors
Adaptability: insensitive to wet travel, capable of transporting multiphase mixed gases such as liquid containing gases, dust containing gases, and easily polymerized gases. Suitable for situations where casing gases may contain small amounts of liquid or impurities. But there are certain requirements for the cleanliness of the gas, and effective intake filtration devices need to be equipped
Centrifugal compressor
Pressure range: The pressure ratio usually does not exceed 5, and the boosting capacity is not as good as that of reciprocating. It is suitable for gas recovery in the medium to high pressure range of casing, and multi-stage series connection can achieve higher pressure ratios
Flow range: With a large air volume and a single machine capacity of over 5000kW, it is suitable for high flow casing gas recovery, and the volume flow adjustment range is wide, usually between 10% and 105%, which can meet the flow change requirements under different working conditions
Operating stability: extremely high speed, high mechanical efficiency, smooth operation, low noise, oil-free lubrication, clean exhaust, no need for oil separation, low basic requirements
Maintenance cost: The structure is relatively simple, with few vulnerable parts, low maintenance volume, and long operating cycle. However, once a malfunction occurs, the maintenance cost may be high and professional maintenance techniques and equipment are required. At the same time, it has high technical requirements for installation and maintenance, requiring strict adherence to operating procedures to ensure the normal operation of the equipment
Energy efficiency performance: Under high flow and medium high pressure conditions, the energy efficiency is good, the mechanical efficiency is high, and the energy consumption is low. However, during low flow or low load operation, it is easy to experience surge, resulting in a decrease in efficiency and an increase in energy consumption
Adaptability: Suitable for processing relatively clean and non corrosive gases, with high requirements for gas quality and composition. If the casing gas contains impurities or corrosive components, it may cause damage to components such as impellers and diffusers, affecting the performance and lifespan of the compressor
Screw compressors are commonly used in casing gas recovery for the following reasons:
Pressure and flow adaptability
In terms of pressure, the discharge pressure of screw compressors is generally between 1MPa and 3MPa, which can well meet the pressure requirements of most casing gas recovery in the medium and low pressure range. It has strong overpressure capability, low pulsation of exhaust pressure, no clearance volume, high efficiency, and can stably compress casing gas to the required pressure. It is suitable for different geological conditions and production stages with changes in casing gas pressure.
In terms of flow rate: Its flow range is wide, with a single machine capacity of over 1000kW, which can meet the gas recovery needs of medium to high flow casing. This has good adaptability to the different flow rates of casing gas produced by oil wells with different production rates. Whether it is small and medium-sized oil wells or high production oil wells, suitable screw compressor models can be found to match their casing gas flow rates.
Operational stability
Compact structure, small size, light weight, smooth operation, low vibration, low noise, low foundation requirements, can achieve no foundation operation. In complex environments such as oil well sites, the low requirements for installation foundations make installation more convenient, and the low vibration and low noise characteristics during operation are conducive to reducing the impact on the surrounding environment and reducing the risk of equipment connection loosening and other faults caused by vibration. It is particularly suitable for use as a mobile compressor and can be easily adjusted and used according to the needs of different oil wells.
Maintenance cost and reliability
Maintenance cost: With few components and no vulnerable parts, it operates reliably and has a long lifespan. The interval between major repairs can reach 480000 hours. Compared to reciprocating compressors, it does not require frequent replacement of vulnerable parts such as air valves and piston rings, reducing downtime caused by maintenance and lowering labor and component replacement costs. At the same time, its operation and maintenance are convenient, with a high degree of automation, which can further reduce the operating costs of the equipment.
Reliability: Although its processing technology requirements are high, once it is manufactured and operates normally, its reliability is high. It can provide long-term stable compression power for casing gas recovery, reducing the risk of production interruption caused by equipment failure. It is of great significance for ensuring the continuity of oil well casing gas recovery.
Adaptability to gases
Not sensitive to wet travel, can transport multiphase mixed gases such as liquid containing gases, dust containing gases, and easily polymerized gases. In actual casing gas, there are often small amounts of impurities such as liquid and dust. Screw compressors can adapt well to this gas containing impurities, avoiding frequent failures or performance degradation caused by impurities in the gas, reducing the requirements for intake pretreatment, and improving the adaptability and stability of the entire casing gas recovery system.
Energy efficiency performance
Combined with frequency conversion speed regulation, it can achieve wide range stepless energy regulation, maintain high efficiency in a wide range of operating conditions, and have better energy consumption performance than reciprocating compressors. In the process of casing gas recovery, the operating conditions such as casing gas flow rate and pressure of different oil wells and the same oil well in different production periods may vary. Screw compressors can flexibly adjust operating parameters according to actual operating conditions, maintain high energy efficiency, thereby reducing operating costs, improving energy utilization efficiency, and meeting the requirements of energy conservation and emission reduction.
