The application of piston compressors in wellhead gas is extensive, especially playing a critical role in natural gas extraction, processing, and transportation. Below is a detailed explanation of its specific applications, advantages, and real-world case studies:
1. Wellhead Gas Compression
During natural gas extraction, the pressure of wellhead gas is usually low and insufficient for direct entry into transmission pipelines or processing facilities. Piston compressors increase the gas pressure through mechanical motion, meeting the requirements for subsequent processing or transportation.
Case Study:
In a shale gas field in North America, the wellhead gas pressure was only 0.5-1 MPa, making it unsuitable for direct pipeline transmission. By installing multiple piston compressors, the gas pressure was boosted to over 6 MPa, meeting the requirements for long-distance pipeline transportation. This compression process not only improved gas transportation efficiency but also reduced resource waste caused by wellhead venting.
2. Associated Gas Recovery
During oil and gas field development, low-pressure natural gas (associated gas) is often produced. If vented or flared directly, it not only wastes resources but also causes environmental pollution. Piston compressors can effectively recover this low-pressure gas, compressing it for injection into pipelines or for power generation.
Case Study:
In an oilfield in Xinjiang, China, associated gas was initially flared due to its low pressure. Later, a piston compressor system was introduced to compress the gas to 2.5 MPa for injection into the natural gas pipeline network. This project recovers over 50 million cubic meters of natural gas annually, reducing resource waste and generating economic benefits.
3. Gas Processing and Purification
In natural gas processing plants, piston compressors are used to compress gas to the required pressure for desulfurization, dehydration, and decarbonization processes. Compressed gas is easier to purify, meeting the quality standards for commercial natural gas.
Case Study:
At a natural gas processing plant in Siberia, Russia, piston compressors were used to compress wellhead gas from 1.2 MPa to 4 MPa before it entered the desulfurization unit. This process significantly improved purification efficiency, ensuring that the exported natural gas met international sulfur content standards.
4. Long-Distance Pipeline Transportation
During long-distance pipeline transportation, natural gas loses pressure due to friction, requiring compression stations along the pipeline to maintain pressure. Piston compressors are often used in these stations due to their efficiency and reliability.
Case Study:
In China's "West-East Gas Pipeline" project, multiple compression stations were established along the pipeline, with some stations using piston compressors. These compressors increased the pipeline pressure from 4 MPa to 10 MPa, ensuring the natural gas could be transported thousands of kilometers to eastern regions.
5. Unconventional Natural Gas Development
In unconventional natural gas development, such as shale gas and coalbed methane, wellhead gas pressure is typically low and fluctuates significantly. Piston compressors are the preferred choice for such applications due to their adaptability and high compression ratio.
Case Study:
In a shale gas field in Texas, USA, piston compressors were widely used to compress low-pressure shale gas. Through multi-stage compression, the gas pressure was increased from 0.3 MPa to 8 MPa, meeting the intake requirements for liquefied natural gas (LNG) plants.
6. CO2 Enhanced Oil Recovery and Storage
In oilfield development, CO2 enhanced oil recovery (CO2-EOR) is widely used. Piston compressors are used to compress CO2 to a supercritical state for injection into oil reservoirs to improve crude oil recovery. Additionally, compressors can be used to store CO2 underground, reducing greenhouse gas emissions.
Case Study:
At an oilfield in the North Sea, Norway, piston compressors were used to compress CO2 to over 10 MPa for injection into oil reservoirs. This project stores over 1 million tons of CO2 annually, increasing crude oil production while reducing carbon emissions.
7. Adaptability and Flexibility
Piston compressors can adapt to different gas compositions, pressures, and flow rates, making them suitable for various wellhead gas compression needs. Through multi-stage compression design, the compression ratio can be flexibly adjusted to meet different process requirements.
Case Study:
At a natural gas field in Australia, due to the complex composition of wellhead gas (high levels of CO2 and nitrogen), traditional centrifugal compressors were unsuitable. Piston compressors were ultimately selected, and through multi-stage compression and customized design, efficient gas compression and processing were successfully achieved.
8. Energy Efficiency and Environmental Protection
Modern piston compressors feature advanced designs and materials, offering high compression efficiency and low energy consumption. Additionally, their excellent sealing performance minimizes gas leakage, reducing environmental pollution.
Case Study:
At a natural gas processing plant in Canada, the energy efficiency of new piston compressors improved by 15% compared to traditional equipment, saving over $500,000 in electricity costs annually. Furthermore, their low-leakage design reduced methane emissions, complying with stringent local environmental regulations.
9. Reliability and Ease of Maintenance
Piston compressors are robust and operate stably, capable of long-term reliable performance in harsh wellhead environments. Their maintenance is relatively simple, facilitating routine upkeep and troubleshooting, which reduces downtime and maintenance costs.
Case Study:
At a natural gas field in a desert region in Africa, piston compressors operated continuously for over five years in high-temperature, high-dust environments without major failures. Their modular design allowed for quick on-site maintenance, significantly improving production efficiency.
Conclusion
Piston compressors play a vital role in wellhead gas processing, with their efficiency, reliability, and flexibility making them indispensable in the natural gas industry. Real-world case studies demonstrate that piston compressors are crucial in gas compression, recovery, processing, and transportation, whether in conventional or unconventional natural gas development. They provide strong support for the efficient development and sustainable growth of the energy industry.
