Casing Gas, also known as casing gas, refers to the gas produced from the annular space of oil well casing during the process of oil extraction. These gases typically include hydrocarbon gases such as methane, ethane, propane, as well as possible non hydrocarbon gases such as nitrogen and carbon dioxide. Casing gas is an important resource in the production process of oil wells, and its yield and quality are often affected by various factors such as geological conditions, extraction methods, and well conditions.
In the process of oil extraction, casing gas is usually extracted together with crude oil, and then separated and processed to obtain natural gas and other useful products. The extraction and utilization of casing gas are of great significance for improving the recovery rate of oil wells, increasing economic benefits, and protecting the environment.
In addition, the presence of casing gas may also have an impact on the production safety of oil wells. If there is too much casing gas or improper handling, it may lead to issues such as increased oil well pressure and increased well control risks. Therefore, in the process of oil extraction, it is necessary to properly manage and handle casing gas to ensure the safe production of oil wells.
The recovery methods of casing gas mainly include the following:
1、 Dynamic oil and gas separator recovery method
This method uses a high-pressure hose to connect the outlet of the oil and gas separator to the natural gas compressor, and the inlet valve of the oil collection main line is connected to the outlet of the natural gas compressor. After the use of the casing gas recovery and utilization equipment, the natural gas recovered in the casing can be directly fed into the natural gas compressor through the connecting hose, which can compress the casing gas while separating oil and gas, thereby obtaining high-quality natural gas products. This method is suitable for oil production projects with sufficient funds, large casing gas volume, and strong casing pressure.
2、 Single flow valve recycling method
The single flow valve recovery method uses a single flow valve to separate oil and gas in casing gas. The single flow valve is connected to the oil pipeline and the pressure difference between the inside and outside of the oil pipeline is used for oil and gas separation. When the external pressure is lower than the internal pressure of the casing, the single flow valve can use the pressure difference between them to separate oil and gas. The advantages of this method are that the equipment requirements are simple, the capital requirements are small, and the construction is convenient. It can be used for ground construction and facilitates the oil and gas recovery and utilization of casing gas. However, this method also has some drawbacks, such as the need for the recovery and utilization of casing gas, which requires the internal pressure of the casing to be greater than the external pressure, making it difficult to stabilize the pressure difference, and due to the simplicity of the facility, it is highly susceptible to human damage, posing safety hazards.
3、 Recovery method of internal flow aid lifting valve in pumping well
This technology installs an oil-gas separator below the oil pump and an auxiliary flow lifting valve on the upper part of the oil extraction pipe column (depending on the internal pressure). After the oil pump works, the gas enters the annular space of the oil and gas separator, and the crude oil without gas is extracted by the oil pump. When the internal pressure of the annulus is greater than the pressure inside the lift valve, the crude oil liquid can be effectively lifted by the lift valve. The assisted flow lifting technology effectively utilizes the characteristics of natural gas and can collect a portion of dissolved gas, reducing the number of times workers open and close valves, lowering workload, and saving funds. But this method is usually only applicable to oil and gas wells with high air pressure, and there is a certain casing pressure at the wellhead, which cannot be used for oil well hot washing work.
4、 Other recycling methods
In addition to the above methods, there are also other casing gas recovery methods, such as suspension type casing gas recovery devices, self-control casing gas recovery devices, etc. These methods are selected and applied based on the specific situation and needs of the oil well to achieve effective recovery and utilization of casing gas.
In general, the recovery method of casing gas needs to be selected and applied according to the actual situation and needs of the oil well. In the implementation of the recycling process, it is necessary to ensure the safety and reliability of the recycling system, and avoid harm to the environment and personnel. At the same time, it is necessary to properly handle and utilize the recovered casing gas to achieve maximum resource utilization and environmental protection.
The recovery methods of casing gas mainly include dynamic oil and gas separator recovery method, single flow valve recovery method, internal flow assist lifting valve recovery method in pumping wells, and other methods. Here is a comparison of these methods:
1、 Equipment investment and cost
Dynamic oil and gas separator recovery method:
The equipment investment is relatively large, requiring supporting equipment such as high-pressure hoses, oil and gas separators, and natural gas compressors.
Suitable for oil production projects with sufficient funds, large casing gas volume, and strong casing pressure.
Single flow valve recycling method:
The equipment requirements are concise and require minimal funding.
Convenient construction, allowing for ground construction and facilitating the oil and gas recovery and utilization of casing gas.
Recovery method of internal flow aid lifting valve in pumping well:
It is necessary to install an oil-gas separator below the oil pump and an auxiliary flow lifting valve on the upper part of the oil extraction pipe column. The equipment investment depends on the specific situation.
Suitable for oil and gas wells with high air pressure, but there are limitations on the hot washing work of oil wells.
2、 Recycling efficiency and stability
Dynamic oil and gas separator recovery method:
High recycling efficiency, able to obtain high-quality natural gas products under pressure.
The stability is good, but regular maintenance and inspection of the equipment are required.
Single flow valve recycling method:
The recycling efficiency is affected by the pressure difference inside and outside the casing, and the size of the pressure difference is difficult to stabilize.
Due to the simplicity of the facilities, they may be susceptible to human damage and pose safety hazards.
Recovery method of internal flow aid lifting valve in pumping well:
The recovery efficiency is affected by the pressure of the oil well and the performance of the lift valve.
The stability is good, but it is necessary to set the position and pressure parameters of the auxiliary flow lifting valve reasonably.
3、 Scope and Limitations of Application
Dynamic oil and gas separator recovery method:
Suitable for oil production projects with high casing gas volume and strong casing pressure.
High requirements for environmental conditions and equipment.
Single flow valve recycling method:
Suitable for oil wells of various sizes, but with certain requirements for the pressure difference inside and outside the casing.
Ground construction is convenient, but there are certain limitations on geological conditions.
Recovery method of internal flow aid lifting valve in pumping well:
Suitable for oil and gas wells with high air pressure.
There is a certain amount of casing pressure at the wellhead, making it impossible to carry out oil well hot washing work.
4、 Comprehensive comparison
The dynamic oil and gas separator recovery method performs well in terms of recovery efficiency and stability, but the equipment investment and cost are high, making it suitable for oil production projects with sufficient funds, large casing gas volume, and strong casing pressure.
The single flow valve recovery method has simple equipment requirements and convenient construction, but the recovery efficiency is affected by pressure differences and there are safety hazards. It is suitable for oil wells with low capital requirements and good geological conditions.
The internal flow assisted lifting valve recovery method in oil extraction wells utilizes the characteristics of natural gas for recovery, reducing the number of times workers open and close valves and reducing workload. However, its applicability is limited and it has limitations on the hot washing work of oil wells.
In summary, when selecting casing gas recovery methods, it is necessary to choose and apply them based on the actual situation and needs of the oil well. At the same time, factors such as equipment investment, recycling efficiency, stability, applicability, and safety and environmental protection also need to be considered.
