What are the classification and design principles of wellhead equipment?

What are the classification and design principles of wellhead equipment?
Wellhead devices are important equipment used in the process of oil and gas extraction to control the pressure, flow rate, and other parameters of oil and gas wellheads. According to its purpose and structural characteristics, wellhead devices can be divided into two categories: temporary wellhead devices and permanent wellhead devices. The following will provide a detailed introduction to the classification and design principles of wellhead equipment.
1、 Temporary wellhead equipment
Temporary wellhead devices, also known as preliminary sealing devices, are used in drilling operations of gas wells or oil wells to temporarily seal and control wellhead pressure. Temporary wellhead equipment usually consists of wellhead plug valve, wellhead safety valve, mud nozzle, foam cup, check valve, etc.
1. Wellhead blockage valve (BOP)
The wellhead blockage valve is a key device used to seal the wellhead. According to its structural characteristics, wellhead blockage valves can be divided into two types: residual pressure relief (RPBOP) and full gate (FGBOP). The residual pressure relief wellhead blockage valve has the function of automatically releasing residual pressure, and has the advantages of good sealing performance, safety and reliability; The full gate wellhead blocking valve has the characteristics of reliable sealing, high working pressure, and good sand resistance.
2. Wellhead Safety Valve (SCSSV)
The wellhead safety valve is used to control the wellhead production capacity and protect the pipeline from leakage and explosion. Wellhead safety valves can be divided into electric wellhead safety valves and pressure balanced wellhead safety valves based on their working methods. The electric wellhead safety valve is operated through a remote control system, which has the characteristics of easy operation and high reliability; The pressure balanced wellhead safety valve is automatically controlled based on the pressure difference at the wellhead, and has the characteristics of simple operation and good pressure balance.
3. Mud spray pipe
Mud nozzles are used to clean and flush the wellhead of oil and gas wells during drilling operations, preventing wellhead blockage and mud infiltration. Mud nozzles can be divided into two types based on their position: wellhead nozzles and main nozzles. The wellhead nozzle is connected to the wellhead blockage valve and used to spray mud to clean the wellhead; The main nozzle is connected to the wellhead pipeline and used to spray mud to flush the surrounding area of the wellhead.
4. foam cup
The foam cup is used to plug the wellhead and reduce the loss of mud, so as to prevent the mud floating from reducing the blowout prevention effect. There are many kinds of foam cups, including hard foam cups and soft foam cups. The hard foam cup is made of metal material, which has the characteristics of high temperature resistance and wear resistance; The soft foam cup is made of rubber material, which has the characteristics of good sealing and acid and alkali corrosion resistance.
5. Check valve
Check valves are used to prevent backflow of wellhead pressure and protect the normal operation of equipment such as oil pumps. Check valves can be divided into two types based on their working principle: one-way check valves and ball check valves. A one-way check valve achieves one-way fluid flow through the up and down movement of the valve disc; The ball check valve controls the one-way flow of fluid through the lifting motion of the ball.
2、 Permanent wellhead equipment
The permanent wellhead device is mainly used in the production process of oil wells to control the wellhead flow rate and oil and gas pressure. Permanent wellhead equipment usually consists of wellhead valves, tubing heads, etc.
1. Wellhead valve
Wellhead valves are used to control wellhead flow and oil and gas pressure. There are three commonly used types of wellhead valves: ball type, gate type, and butterfly type. Ball type wellhead valves have the characteristics of simple structure and low flow resistance; Gate type wellhead valves have the characteristics of good sealing and long service life; Butterfly wellhead valves have the characteristics of small volume and easy operation.
2. Oil pipe head
The tubing head is a connecting device between the wellhead and the tubing, used to regulate the wellhead pressure and oil and gas flow rate. There are three commonly used types of tubing heads: balanced tubing heads, bent tubing heads, and finned tubing heads. The balanced tubing head controls the tubing pressure by adjusting the pressure difference between the inside and outside of the tubing; The bending head controls the pressure of the oil pipe by adjusting the angle of the diffusion plate; The fin tube head controls the pressure of the oil pipe by adjusting the opening and closing of the fins.
Design principles
1. Safety principles
The design of wellhead equipment should comply with safety principles to ensure stable and reliable operation of wellhead equipment under harsh conditions such as high pressure and high flow rate, and to prevent safety accidents such as wellhead leakage and explosion.
2. Reliability principle
The design of wellhead equipment should adhere to the principle of reliability, ensuring that the wellhead equipment can work stably and continuously for a long time, reducing the frequency of maintenance and equipment replacement, and improving production efficiency.
3. Flexibility principle
The design of wellhead equipment should follow the principle of flexibility, and can be adjusted and changed according to changes in wellhead parameters to adapt to different working conditions.
4. Economic principle
The design of wellhead equipment should adhere to the principle of economy, select materials and structures reasonably, reduce manufacturing and maintenance costs, and improve the service life of the equipment.
5. Compatibility principle
The design of wellhead equipment should have compatibility principles, be able to cooperate well with other equipment and systems, achieve interconnection, and improve the efficiency and safety of the entire production system.
In summary, wellhead devices can be divided into two categories based on their purpose and structural characteristics: temporary wellhead devices and permanent wellhead devices. Its design principles include safety, reliability, flexibility, economy, and compatibility. By designing and selecting wellhead equipment reasonably, the safety and efficiency of the oil and gas extraction process can be ensured.