When recovering casing gas, there are several requirements for the compressor, including:
Pressure requirements
Suction pressure range: The compressor needs to be able to adapt to the lower initial pressure of the casing gas. Generally speaking, the pressure of casing gas may range from a few kPa to several hundred kPa, and the suction pressure range of the compressor should be able to cover this range to ensure effective suction of casing gas. For example, the suction pressure of some reciprocating compressors can be as low as 10kPa, which can better meet the initial pressure requirements for casing gas recovery.
Discharge pressure capability: The recovered casing gas usually needs to be compressed to a certain high pressure for subsequent storage, transportation, or reuse. The discharge pressure of the compressor should be determined according to the specific recovery system and usage requirements, generally ranging from 1MPa to several MPa. Like a screw compressor, a higher discharge pressure can be achieved through multi-stage compression, meeting the need to compress the casing gas to the required high pressure state.
Traffic requirements
Matching processing capacity: The flow rate of the compressor should match the amount of gas produced in the casing. The amount of casing gas produced varies depending on factors such as oil well production and casing pressure. The compressor should have corresponding processing capabilities to ensure timely and effective recovery of the produced casing gas, avoiding waste and environmental pollution caused by gas accumulation or discharge. For example, for oil wells with high daily gas production, it may be necessary to use centrifugal compressors with high flow rates to meet the requirements of casing gas recovery.
Flow regulation range: In order to adapt to the changes in the amount of casing gas produced under different working conditions, the compressor needs a wide flow regulation range. In the early, middle, and later stages of oil well production, the production of casing gas may vary. The compressor should be able to flexibly adjust the flow rate within a certain range to ensure stable operation under various working conditions and achieve efficient gas recovery. Some advanced compressors are equipped with variable frequency speed control devices, which can automatically adjust the speed according to the actual gas demand, thereby achieving a wide range of flow regulation.
Gas composition adaptability requirements
Corrosion gas response: The casing gas may contain corrosive gas components such as hydrogen sulfide and carbon dioxide. The material and internal structure of the compressor should be able to withstand the erosion of these corrosive gases, preventing equipment damage due to corrosion and affecting its service life and operational safety. For example, for casing gases containing hydrogen sulfide, corrosion-resistant stainless steel materials are usually used to manufacture key components of the compressor, such as impellers, cylinders, etc., to ensure reliable operation of the compressor in corrosive environments.
Impurity tolerance: The casing gas may also carry small amounts of solid particles, droplets, and other impurities. The compressor needs to have a certain tolerance for impurities to prevent them from entering the interior of the compressor and causing problems such as wear and blockage. Generally, a filter is installed at the inlet of the compressor to preliminarily filter the gas. However, the design of the compressor itself should also consider the influence of impurities, such as using wear-resistant sealing materials and designing gas flow channels reasonably to reduce the impact of impurities on the performance of the compressor.
Reliability and stability requirements
Continuous operation capability: In the process of casing gas recovery, it is usually required that the compressor can operate continuously and stably for a long time to ensure the continuity and stability of gas recovery. The key components of the compressor should have good wear resistance, fatigue resistance, and reliability to reduce downtime caused by malfunctions. For example, large centrifugal compressors adopt advanced bearing technology and lubrication systems, which can ensure long-term stable operation at high speeds and meet the requirements of continuous operation of equipment for casing gas recovery.
Environmental adaptability: Compressors need to adapt to different working environments, including high temperature, low temperature, humidity, and other conditions. In some remote oil well areas with harsh environmental conditions, compressors should be able to operate normally in these environments without being affected by external factors. For example, compressors used in cold regions need to be equipped with heating devices and low-temperature start-up protection systems to ensure smooth start-up and operation in low-temperature environments.
Security requirements
Explosion proof design: Due to the flammability and explosiveness of the casing gas, the compressor must have explosion-proof performance. This includes the use of explosion-proof motors, explosion-proof electrical components, explosion-proof control systems, etc., to prevent gas explosion accidents caused by electrical sparks, etc. At the same time, the overall structural design of the compressor should comply with explosion-proof standards to avoid safety accidents caused by sparks or high temperatures due to mechanical failures.
Leak detection and protection: In order to prevent safety hazards and environmental pollution caused by casing gas leakage, compressors should be equipped with reliable leak detection devices and protective measures. For example, installing a gas leak sensor to monitor the gas concentration around the compressor in real time. Once a leak occurs, it can promptly issue an alarm and take corresponding emergency measures. In addition, the sealing system of the compressor should have good sealing performance to reduce the possibility of gas leakage.
Choosing a compressor model suitable for casing gas recovery requires comprehensive consideration of multiple factors. The following are some key selection points:
Gas characteristics
Pressure range: Clearly define the initial pressure of the casing gas and the final pressure that needs to be compressed to. The performance of different types of compressors varies under different pressure ranges. Generally speaking, reciprocating compressors are suitable for medium to low pressure ranges, with suction pressures as low as around 10kPa and discharge pressures up to several MPa; Centrifugal compressors are more suitable for medium to high pressure and high flow conditions, with discharge pressures ranging from several hundred kPa to tens of MPa; Screw compressors have a wide pressure range and can operate at lower suction pressures. The discharge pressure can also reach a certain height, usually between 1MPa and 3MPa. Select the compressor model that can effectively cover the pressure range based on the actual pressure situation of the casing gas.
Flow demand: Accurately evaluate the amount of gas produced in the casing, that is, the flow rate size. If the gas flow rate of the casing is small, a small reciprocating compressor or screw compressor can be used; If the flow rate is large, a centrifugal compressor or a large screw compressor may be more suitable. For example, when the gas flow rate of the casing is below tens of cubic meters per hour, a small reciprocating compressor can meet the requirements; When the flow rate exceeds several hundred cubic meters per hour, centrifugal compressors have better processing capacity and efficiency. At the same time, it is necessary to consider the flow regulation range of the compressor to adapt to changes in the amount of gas produced by the casing. Some compressors with variable frequency speed regulation function can achieve flexible adjustment within a wide flow range, better matching the flow requirements under different working conditions.
Gas composition: Analyze whether the casing gas contains corrosive gases (such as hydrogen sulfide, carbon dioxide, etc.), impurities (such as solid particles, droplets, etc.), and their content. For casing gases containing corrosive gases, compressor materials with good corrosion resistance should be selected, such as stainless steel impellers, cylinders, and other components of the compressor. If there are many impurities in the gas, an efficient filter should be installed at the inlet of the compressor, and a compressor model with strong tolerance to impurities should be selected. Its internal structural design should be able to prevent impurities from entering key parts and causing wear, blockage, and other problems.
Operating environment
Temperature conditions: Consider the temperature range of the working environment of the compressor. In high temperature environments, the cooling system of the compressor needs to work effectively to prevent equipment overheating; In low-temperature environments, compressors should have good low-temperature starting performance and anti freezing measures. For example, compressors used in hot desert areas require powerful air-cooled or water-cooled cooling systems; In cold polar regions, compressors need to be equipped with heating devices, low-temperature lubricating oil, and appropriate insulation measures to ensure normal start-up and operation under low temperature conditions. Select compressor models with corresponding environmental adaptability based on actual temperature conditions.
Space limitation: Choose the appropriate size of compressor based on the space size of the installation site. If the installation space is limited, you can choose compressor models with smaller volume and compact structure, such as small screw compressors or vertical reciprocating compressors; If the space is spacious, the more suitable compressor type can be prioritized based on other performance requirements, without being overly limited by size. At the same time, it is necessary to consider the maintenance space of the compressor to ensure that daily maintenance and repairs can be easily carried out during equipment operation.
Reliability and maintenance requirements
Reliability: Casing gas recovery typically requires the compressor to be able to operate continuously and stably for a long time, so the reliability of the compressor is crucial. Choose brands and models with good reputation and market validation, and check the quality and durability of their key components, such as compressor motors, bearings, seals, etc. Generally speaking, compressors from well-known brands have stricter design, manufacturing, and quality control, which can provide higher reliability and stability. For example, some large centrifugal compressors adopt advanced bearing technology and lubrication systems, which can effectively reduce the occurrence rate of failures and ensure reliability during long-term operation.
Maintenance difficulty and cost: Different types and models of compressors have differences in maintenance difficulty and cost. The structure of reciprocating compressors is relatively complex, with many components and a large maintenance workload, but the maintenance cost is relatively low; Centrifugal compressors have a relatively simple structure, operate smoothly, and require less maintenance. However, once a malfunction occurs, the maintenance cost may be higher; Screw compressors fall between the two. When selecting a compressor model, it is necessary to comprehensively consider the maintenance technology level and cost budget of the enterprise, and choose a compressor that is easy to maintain and has reasonable maintenance costs. At the same time, the replacement cycle and cost of vulnerable parts of the compressor should also be considered, as well as whether there is reliable after-sales service and spare parts supply to ensure that the compressor can be repaired and replaced in a timely manner in case of failure.
energy efficiency
Energy efficiency rating: Pay attention to the energy efficiency rating of the compressor, and choose models with higher energy efficiency to reduce operating costs. At present, many countries and regions have corresponding energy efficiency standards and labels for compressors, which can be used to evaluate the energy efficiency of different models of compressors. Generally speaking, new centrifugal compressors and screw compressors perform well in terms of energy efficiency. By optimizing their design and adopting advanced control technologies, they can achieve high energy utilization efficiency under different operating conditions.
Power matching: Reasonably select the power of the compressor based on the actual needs of the casing gas recovery system. Excessive power not only increases equipment investment costs, but may also lead to energy waste; If the power is too low, it cannot meet the requirements of gas compression and affects the recovery efficiency. When selecting compressor power, it is necessary to comprehensively consider factors such as gas flow rate, pressure variation range, and compressor operating efficiency. Through accurate calculation and simulation, the power that matches the system requirements should be selected to achieve the best energy utilization effect.
Investment cost
Equipment procurement cost: The prices of compressors of different models and specifications vary greatly. On the premise of meeting the requirements of casing gas recovery, suitable compressors need to be selected according to the budget of the enterprise. Generally speaking, the procurement cost of reciprocating compressors is relatively low, making them suitable for projects that are sensitive to investment costs; Centrifugal compressors and large screw compressors have higher procurement costs, but they have better performance and efficiency in handling high flow, high-pressure casing gases. When comparing the procurement costs of different types of compressors, it is not enough to only focus on the price of the equipment itself, but also to comprehensively consider factors such as performance, reliability, and service life, and conduct a comprehensive cost-effectiveness evaluation.
Operating costs: In addition to equipment procurement costs, the operating costs of the compressor also need to be considered, including energy consumption, maintenance costs, spare parts replacement costs, etc. Although compressors with higher energy efficiency may have higher procurement costs, they can save a significant amount of energy costs during long-term operation; A compressor with simple maintenance and low cost of replacing vulnerable parts can reduce maintenance costs during operation. By conducting a detailed analysis and comparison of the operating costs of different types of compressors, the compressor model with the lowest comprehensive cost is selected to maximize the economic benefits of the project.
