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About wellhead equipment,You should know these...

13 May.,2024

 

About wellhead equipment,You should know these...

Overview

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Wellhead equipments refer to Christmas trees, tubing heads, casing heads and related accessories, and are oil production equipment used for suspension, support, control, and adjustment. As an important equipment for oil and gas production, its performance is related to the safe and efficient production of oil and gas wells.

Casing Head

The casing head is an important connection between the casing and the wellhead. Its lower end is connected with the surface casing through a thread, and the upper end is connected with a wellhead device or a blowout preventer through a flange or a clamp.

Features of casing head

The casing connection can adopt thread connection or slip connection, so that the casing is fast and convenient to hang;

The casing hanger adopts a rigid and rubber compound sealing structure, and can also adopt a metal seal, which enhances the sealing performance of the product;

Designed with anti-wear sleeve and pressure test removal tool to facilitate the removal of the anti-wear sleeve and pressure test on the casing head;

The upper flange is designed with pressure test and secondary grease injection device;

The flank valve configuration of the casing head is designed according to user requirements;

The role of casing head

The casing head is installed at the upper end of the surface casing string to suspend all layers of casing other than the surface casing and to seal the casing annular space. The main functions are as follows

1. Hang part or all of the weight of each layer of casing except the surface casing through the hanger;

2. Connect wellhead devices such as blowout preventers;

3. Form a pressure seal between the inner and outer casing strings;

4. Provide an outlet for releasing the pressure that may accumulate between 20% of the casing strings;

5. In an emergency, fluid, such as killing fluid or fire extinguishing agent, can be pumped into the well through the side hole of the casing head;

6. Special operations: a. The cementing quality is not good, but the side holes can be refilled with cement. b. When acidizing fracturing, pressure balance fluid can be injected from the side holes.

For easy memory, the function and purpose of the casing head are summarized into four sentences:

Hanging the weight of each layer of casing;

Support the blowout preventer above the casing head;

Provide a seal between each layer of casing;

Provide channels for special operations;

Classification of casing head

1. According to the number of hanging casing layers

    According to the number of suspended casing layers, it can be divided into: single-stage casing head, double-stage casing head, and three-stage casing head; among them, single-stage casing head is generally used in production wells in low-pressure shallow formations; double-stage casing head It is suitable for most areas with relatively clear formation pressure and is used in a large amount; three-stage casing heads are generally used in high-pressure deep wells or exploration wells;

2. According to the structure of the casing hanger

    According to the structure of the casing hanger, it can be divided into slip type casing head, mandrel type (threaded) casing head, and integral (welded) casing head;

3. According to the connection between the main bodies

    According to the connection between the bodies, it is divided into flange type casing head, clamp type casing head and independent thread type (the upper end of the suspension casing string and the lower end of the tubing head body are connected by threads);


4. According to the structure of the body

     According to the structure of the main body, it is divided into single casing head (one body is equipped with one hanger) and combined casing head (one body is equipped with multiple hangers);

Structure and sealing of casing head

1. The structure of the casing head

  The casing head is composed of four-way, casing hanger, jacking wire assembly, flange type parallel gate valve, connector, pressure display mechanism, etc.;

2. Working principle of rubber seal

  The casing head seal is composed of casing head body, BT-shaped rubber seal ring, casing hanger, dovetail rubber seal ring, top wire V-shaped seal ring, and gasket ring. The casing hanger seat is hung on the casing head body. On the steps, due to the hanging weight of the casing, the metal-to-metal contact produces a rigid passive seal. The casing hanger and the casing are sealed by threaded seals.

   The casing head four-way has a BT seal that matches the outer diameter of the casing hanger (or casing outer diameter) and the corresponding grease injection and pressure test holes. High pressure sealing grease must be injected from the grease injection valve during use. The BT seal works. If the seal leaks, seal grease should be injected separately from the grease injection valve and the pressure test valve to make the seal continue to take effect. The grease injection pressure shall not exceed the rated working pressure of the flange; if the casing is sealed, it shall not exceed the rated allowable collapse pressure of the casing. The pressure test hole is used for the external sealing test of the casing hanger.

   There is a top wire on the flange to lock the anti-wear sleeve (to protect the sealing surface). After the casing hanger is seated, the casing hanger can be locked. If leakage occurs at the top wire, the compression cap can be tightened to make the seal effective. Four-way flanges on both sides of the casing head, one end is connected to a flat valve (or blind flange), and the other end is connected to a flat valve, threaded flange, joint, stop valve and pressure gauge. The two casing layers can be observed by the pressure gauge. Annulus pressure between.

3. Metal and rubber seal of casing head

   The metal and rubber seal of the casing head consists of the casing head body, BT-shaped rubber seal ring, upper metal seal assembly, lower metal seal assembly, casing hanger, dovetail rubber seal ring, top wire V-shaped seal ring, and gasket ring The casing hanger is hung on the step of the casing head body. Due to the hanging weight of the casing, the metal-to-metal contact produces a rigid passive seal. The seal between the casing hanger and the casing is threaded seal (see the above figure); the upper metal sealing ring is to measure the position and size of the upper metal sealing ring in the upper flange hole before installing the upper flange, and then determine the installation adjustment The thickness of the ring makes the adjustment ring have a certain amount of interference in the upper flange hole. When the upper flange is connected with the four-way casing head, the adjusting ring is compressed by the four-way casing head to deform the upper metal sealing ring, thereby achieving the function of sealing the casing hanger.

  The sealing principle of the lower metal sealing component of the casing hanger is to ensure the geometric dimensions of each part through the design of the metal sealing ring, the casing head four-way, and the casing hanger. The 45° cone rotation on the top wire is used. The pressure ring of the lower metal seal assembly is moved down, and the U-shaped ring of the metal seal ring assembly is deformed, thereby achieving the function of sealing the casing hanger.

Casing head hanger

1. Mandrel hanger

   The mandrel type (ie threaded type) hanger is equivalent to a casing coupling, no need to cut the casing (W and WE type are required), save trouble, and can even hang the casing without opening the blowout preventer to solve the wellhead suspension sealing problem . However, it is necessary to calculate the casing depth to avoid bottoming. Generally used in relatively stable production wells. Generally, the mandrel-type (threaded) hanger is used with the threaded casing head, and the corresponding slip-type hanger can also be replaced. The sealing principle of the mandrel hanger with metal and rubber seal on the casing head is the same as that of the mandrel hanger with metal and rubber seal on the tubing head.

2. Slip hanger

a. The structure of slip hanger:

  The slip hanger is mainly composed of slips (four equal parts), slip seat (two equal parts), rubber seal (two equal parts), and support seat (two equal parts).

b. Working principle of slip hanger:

  The two halves of the combined slip hanger hug the casing, and put it into the casing head hole as a whole to make the slips clamp the casing tightly. Under the action of the self-weight of the casing and the taper of the slips, the slips The more the wedges are, the tighter they are, and the tighter the slips are to the casing. The rubber seal is deformed under its own weight to form a seal between the casing and the casing head body.

c. Inverted slip hanger

    The inverted slip hanger seat is bolted to the lower part of the casing head body. The slips are put down after the casing is installed in the BT sealing ring, so that the slips can be tightly clamped to the casing. The effect of the self-weight and taper of the casing , The more wedged the slips, the tighter the slips, the tighter the slips against the casing.

Slip hanger

1. WE type slip hanger:

   Generally speaking, the WE type slip hanger is used for the surface layer, and its characteristics are: large size, the sealing ring air pressure is not too high (compared to the W type). Another situation is: the casing cannot be lifted and lowered by cementing (this is a prerequisite for the W type hanger), WE can be passive (the casing does not move, the hanger is movable and sealed, and the seal is activated manually instead of by the hanging weight. ) The installation is sealed and remedied. If you don't care about factors such as hanging weight and sealing, WE type and W type with the same size and the same manufacturer can generally be interchanged.

2. W type casing hanger

    Compared with the WE type, it relies on the suspended weight of the drill string to activate the sealing. It is characterized by the largest suspension tonnage, better sealing, and more stable. It is generally used for the suspension of technical casing.

3. WD type hanger

   It is only used for the surface casing head, the lower part is connected to the surface casing.

Tubing Head

The tubing head is a device or short section with flanges at both ends. Before perforating, install it on top of the uppermost casing head. It is used to support the oil pipe and seal the annular space between the oil pipe and the production casing. It also provides an inlet for the casing and tubing annular space through the side outlet.

Function of tubing head Suspend the tubing string in the well. Seal the annular space between the tubing and the casing. Provide transitional connections for casing head and Christmas tree. The two side ports on the tubing head cross can be used for water injection and well washing operations.

Structural composition of tubing head

    The tubing head consists of tubing head cross, tubing hanger, sealing device, jacking wire, gate valve, pressure gauge and flange. The top of the tubing head is connected to the Christmas tree through a special-shaped flange. The connection forms include flange type and clamp type.

1). Tubing hanger

The tubing hanger is a device that sits in the cone seat of the tubing head and is used to suspend the tubing string and provide a seal between the suspended tubing and the tubing head cone seat. Offshore oil and gas completions generally have downhole safety valves. Therefore, tubing hangers must have channels for connecting hydraulic control pipelines. Electric submersible pump wells must also have downhole vent valve channels and cables to pass through and be sealed. After connecting the oil pipes to form a circular whole, sit in the double oil pipe hanger seat, and you must align with the guide block on the oil pipe row seat when sitting in


2). Tubing head cross

About wellhead equipmentwellhead equipment,You should know these...

Overview

Wellhead equipments refer to Christmas trees, tubing heads, casing heads and related accessories, and are oil production equipment used for suspension, support, control, and adjustment. As an important equipment for oil and gas production, its performance is related to the safe and efficient production of oil and gas wells.

Casing Head

The casing head is an important connection between the casing and the wellhead. Its lower end is connected with the surface casing through a thread, and the upper end is connected with a wellhead device or a blowout preventer through a flange or a clamp.

Features of casing head

The casing connection can adopt thread connection or slip connection, so that the casing is fast and convenient to hang;

The casing hanger adopts a rigid and rubber compound sealing structure, and can also adopt a metal seal, which enhances the sealing performance of the product;

Designed with anti-wear sleeve and pressure test removal tool to facilitate the removal of the anti-wear sleeve and pressure test on the casing head;

The upper flange is designed with pressure test and secondary grease injection device;

The flank valve configuration of the casing head is designed according to user requirements;

The role of casing head

The casing head is installed at the upper end of the surface casing string to suspend all layers of casing other than the surface casing and to seal the casing annular space. The main functions are as follows

1. Hang part or all of the weight of each layer of casing except the surface casing through the hanger;

2. Connect wellhead devices such as blowout preventers;

3. Form a pressure seal between the inner and outer casing strings;

4. Provide an outlet for releasing the pressure that may accumulate between 20% of the casing strings;

5. In an emergency, fluid, such as killing fluid or fire extinguishing agent, can be pumped into the well through the side hole of the casing head;

6. Special operations: a. The cementing quality is not good, but the side holes can be refilled with cement. b. When acidizing fracturing, pressure balance fluid can be injected from the side holes.

For easy memory, the function and purpose of the casing head are summarized into four sentences:

Hanging the weight of each layer of casing;

Support the blowout preventer above the casing head;

Provide a seal between each layer of casing;

Provide channels for special operations;

Classification of casing head

1. According to the number of hanging casing layers

    According to the number of suspended casing layers, it can be divided into: single-stage casing head, double-stage casing head, and three-stage casing head; among them, single-stage casing head is generally used in production wells in low-pressure shallow formations; double-stage casing head It is suitable for most areas with relatively clear formation pressure and is used in a large amount; three-stage casing heads are generally used in high-pressure deep wells or exploration wells;

2. According to the structure of the casing hanger

    According to the structure of the casing hanger, it can be divided into slip type casing head, mandrel type (threaded) casing head, and integral (welded) casing head;

3. According to the connection between the main bodies

    According to the connection between the bodies, it is divided into flange type casing head, clamp type casing head and independent thread type (the upper end of the suspension casing string and the lower end of the tubing head body are connected by threads);


4. According to the structure of the body

     According to the structure of the main body, it is divided into single casing head (one body is equipped with one hanger) and combined casing head (one body is equipped with multiple hangers);

Structure and sealing of casing head

1. The structure of the casing head

  The casing head is composed of four-way, casing hanger, jacking wire assembly, flange type parallel gate valve, connector, pressure display mechanism, etc.;

2. Working principle of rubber seal

  The casing head seal is composed of casing head body, BT-shaped rubber seal ring, casing hanger, dovetail rubber seal ring, top wire V-shaped seal ring, and gasket ring. The casing hanger seat is hung on the casing head body. On the steps, due to the hanging weight of the casing, the metal-to-metal contact produces a rigid passive seal. The casing hanger and the casing are sealed by threaded seals.

   The casing head four-way has a BT seal that matches the outer diameter of the casing hanger (or casing outer diameter) and the corresponding grease injection and pressure test holes. High pressure sealing grease must be injected from the grease injection valve during use. The BT seal works. If the seal leaks, seal grease should be injected separately from the grease injection valve and the pressure test valve to make the seal continue to take effect. The grease injection pressure shall not exceed the rated working pressure of the flange; if the casing is sealed, it shall not exceed the rated allowable collapse pressure of the casing. The pressure test hole is used for the external sealing test of the casing hanger.

   There is a top wire on the flange to lock the anti-wear sleeve (to protect the sealing surface). After the casing hanger is seated, the casing hanger can be locked. If leakage occurs at the top wire, the compression cap can be tightened to make the seal effective. Four-way flanges on both sides of the casing head, one end is connected to a flat valve (or blind flange), and the other end is connected to a flat valve, threaded flange, joint, stop valve and pressure gauge. The two casing layers can be observed by the pressure gauge. Annulus pressure between.

3. Metal and rubber seal of casing head

   The metal and rubber seal of the casing head consists of the casing head body, BT-shaped rubber seal ring, upper metal seal assembly, lower metal seal assembly, casing hanger, dovetail rubber seal ring, top wire V-shaped seal ring, and gasket ring The casing hanger is hung on the step of the casing head body. Due to the hanging weight of the casing, the metal-to-metal contact produces a rigid passive seal. The seal between the casing hanger and the casing is threaded seal (see the above figure); the upper metal sealing ring is to measure the position and size of the upper metal sealing ring in the upper flange hole before installing the upper flange, and then determine the installation adjustment The thickness of the ring makes the adjustment ring have a certain amount of interference in the upper flange hole. When the upper flange is connected with the four-way casing head, the adjusting ring is compressed by the four-way casing head to deform the upper metal sealing ring, thereby achieving the function of sealing the casing hanger.

  The sealing principle of the lower metal sealing component of the casing hanger is to ensure the geometric dimensions of each part through the design of the metal sealing ring, the casing head four-way, and the casing hanger. The 45° cone rotation on the top wire is used. The pressure ring of the lower metal seal assembly is moved down, and the U-shaped ring of the metal seal ring assembly is deformed, thereby achieving the function of sealing the casing hanger.

Casing head hanger

1. Mandrel hanger

   The mandrel type (ie threaded type) hanger is equivalent to a casing coupling, no need to cut the casing (W and WE type are required), save trouble, and can even hang the casing without opening the blowout preventer to solve the wellhead suspension sealing problem . However, it is necessary to calculate the casing depth to avoid bottoming. Generally used in relatively stable production wells. Generally, the mandrel-type (threaded) hanger is used with the threaded casing head, and the corresponding slip-type hanger can also be replaced. The sealing principle of the mandrel hanger with metal and rubber seal on the casing head is the same as that of the mandrel hanger with metal and rubber seal on the tubing head.

2. Slip hanger

a. The structure of slip hanger:

  The slip hanger is mainly composed of slips (four equal parts), slip seat (two equal parts), rubber seal (two equal parts), and support seat (two equal parts).

b. Working principle of slip hanger:

  The two halves of the combined slip hanger hug the casing, and put it into the casing head hole as a whole to make the slips clamp the casing tightly. Under the action of the self-weight of the casing and the taper of the slips, the slips The more the wedges are, the tighter they are, and the tighter the slips are to the casing. The rubber seal is deformed under its own weight to form a seal between the casing and the casing head body.

c. Inverted slip hanger

    The inverted slip hanger seat is bolted to the lower part of the casing head body. The slips are put down after the casing is installed in the BT sealing ring, so that the slips can be tightly clamped to the casing. The effect of the self-weight and taper of the casing , The more wedged the slips, the tighter the slips, the tighter the slips against the casing.

Slip hanger

1. WE type slip hanger:

   Generally speaking, the WE type slip hanger is used for the surface layer, and its characteristics are: large size, the sealing ring air pressure is not too high (compared to the W type). Another situation is: the casing cannot be lifted and lowered by cementing (this is a prerequisite for the W type hanger), WE can be passive (the casing does not move, the hanger is movable and sealed, and the seal is activated manually instead of by the hanging weight. ) The installation is sealed and remedied. If you don't care about factors such as hanging weight and sealing, WE type and W type with the same size and the same manufacturer can generally be interchanged.

2. W type casing hanger

    Compared with the WE type, it relies on the suspended weight of the drill string to activate the sealing. It is characterized by the largest suspension tonnage, better sealing, and more stable. It is generally used for the suspension of technical casing.

3. WD type hanger

   It is only used for the surface casing head, the lower part is connected to the surface casing.

Tubing Head

The tubing head is a device or short section with flanges at both ends. Before perforating, install it on top of the uppermost casing head. It is used to support the oil pipe and seal the annular space between the oil pipe and the production casing. It also provides an inlet for the casing and tubing annular space through the side outlet.

Function of tubing head Suspend the tubing string in the well. Seal the annular space between the tubing and the casing. Provide transitional connections for casing head and Christmas tree. The two side ports on the tubing head cross can be used for water injection and well washing operations.

Structural composition of tubing head

    The tubing head consists of tubing head cross, tubing hanger, sealing device, jacking wire, gate valve, pressure gauge and flange. The top of the tubing head is connected to the Christmas tree through a special-shaped flange. The connection forms include flange type and clamp type.

1). Tubing hanger

The tubing hanger is a device that sits in the cone seat of the tubing head and is used to suspend the tubing string and provide a seal between the suspended tubing and the tubing head cone seat. Offshore oil and gas completions generally have downhole safety valves. Therefore, tubing hangers must have channels for connecting hydraulic control pipelines. Electric submersible pump wells must also have downhole vent valve channels and cables to pass through and be sealed. After connecting the oil pipes to form a circular whole, sit in the double oil pipe hanger seat, and you must align with the guide block on the oil pipe row seat when sitting in


2). Tubing head cross

       The tubing head cross is the main structure of the tubing head. The bottom of the tubing head cross is connected to the casing head, the top is connected to the Christmas tree, and the top and bottom are sealed with steel rings. The tubing head cross provides a carrier and container for the tubing hanger.

      The tubing head spool is used to perform positive and reverse circulation well flushing to observe the casing pressure, and to perform various operations through the annular space of the oil jacket.

3). Tubing top wire

    After the oil pipe hanger is installed in place, the oil pipe hanger wire must be installed. The function of the tubing hanger wire is to lock the tubing hanger and prevent it from moving up and down and rotating.

3). Top wire flange

      The jack flange is mounted on the casing cross, and the tubing is hung on the seat of the jack flange, and plays the role of squeezing the packing and sealing the annular space of the oil jacket. At the same time, it jams the tubing to prevent excessive pressure in the well. Eject the tubing string when it is high.

X-Mass

Christmas tree concept

     Christmas trees are wellhead devices used to extract oil from blowout wells and mechanical production wells. It is the main equipment for controlling and regulating oil and gas production at the top of oil and gas wells. The Christmas tree is composed of valves, reducers, nozzles and pipe fittings. It is used to control production and repair steel wires, cables, coiled tubing, etc. A device that provides conditions for well operations.

The role of Christmas tree

(1) Connect each layer of casing downhole, seal the annular space of each layer of casing, and bear part of the weight of the casing.

(2) Suspending tubing and downhole tools, supporting the weight of all tubing strings in the well, and sealing the annular space between tubing and casing.

(3) Control and regulate the production of oil wells.

(4) Ensure the construction of various underground operations, facilitate the construction of well killing operations, starting operations and other measures, and carry out daily production management such as pressure measurement and wax removal.

(5) Record oil pressure and casing pressure data.


Christmas tree classification

  According to the structure of the Christmas tree, it can be divided into two types: split type and integral type. Split type is assembled by some independent parts such as valves.

The integral type is to make the main valve, safety valve, wax removal valve and wing valve into an integral part. The distance between the valve and the valve is small, which saves space and is resistant to high pressure. It is especially suitable for oil and gas wells on offshore platforms.

According to the types of production wells and well completion production methods, they can be divided into self-blowing wells, electric submersible pump wells, gas lift wells, screw pump wells, water injection wells, and Christmas trees for gas wells.

Single tube and double tube

1. Single Tubing Christmas Tree

    The single-tubing Christmas tree is installed on the wellhead of a single-tubing completion. In addition to the split type and the integral type, it also has a single wing and a double wing. Depending on the type of well or the production method of the well, valves and pup joints can be combined into different forms of single tubing Christmas tree, and the connection method can be flange type, thread type or clamp type.

2. Double tubing Christmas tree

    The double-tubing Christmas tree is installed on the wellhead of the double-tubing completion, and is used for the production control of the simultaneous and independent exploitation of two oil layers. The dual tubing completion is to run two parallel tubing strings (long tubing string and short tubing string) or two concentric tubing strings in the same production casing, and pair the two tubing strings through a dual-tube packer and a single-tube packer. Separate oil (or gas) intervals.

3. Three-tube Christmas tree

      With the development of technology and actual application requirements on site, three-tube Christmas trees have appeared.

Christmas tree related parts

1. Tubing cross and tee

    The tubing four-way and three-way of the Christmas tree are connected with the main valve, wax removal valve and wing valve. The common four-way and three-way are flanged and flange-studded. The Christmas tree with four links is a double-wing Christmas tree, and the Christmas tree with three links is a single-wing Christmas tree. On some platforms, the three-way Christmas tree is composed of a wax removal valve and a main valve or a wellhead safety valve, which becomes an integral Christmas tree.

2. Gate valve and plug valve

    The gate valve is a valve in which the moving direction of the closing part (gate) is perpendicular to the flow direction. A plug valve is a valve that shuts off the rotation of a component (cock), and the plug can be cylindrical, conical or spherical. Play the role of wellhead control.

3. Grease nipple

    The nozzle is a component used to control the flow of the oil well on the Christmas tree. It is installed between the wing valve and the oil outlet pipeline. The nozzle can also be used to control the gas injection volume of gas lift wells and the water injection volume of water injection wells. The nozzle is a throttling element. The reasonable production pressure difference of the oil well can be controlled by changing nozzles with different hole diameters. The nozzle is made of high-carbon alloy steel after heat treatment. There are many kinds of hole diameter from 2-20mm, each difference of 0.5mm is a grade.

   There are two types of nozzles: fixed and adjustable. The fixed nozzle is equipped with replaceable parts. This part has a fixed hole for throttling. The adjustable nozzle has a small hole of variable area controlled by the outside and a corresponding small hole area indicating mechanism. The orifice of the oil nozzle is a small hole distributed on the tubular part, and the change in the number of the small holes covered by the outer sleeve of the tubular part is the change in the flow area.

4. Check valve

     A check valve is a valve that only allows fluid to flow freely in one direction, so it is also called a check valve. The check valve has a mechanism that automatically prevents fluid from flowing in other directions. The check valve on the Christmas tree is generally installed between the wing valve and the nozzle. There is no check valve installed on the Christmas tree in some oil wells, but a check valve is generally installed on the Christmas tree in the water injection well. The check valve has oil outlet pipe type, swing open type, rising rod type and butterfly type. The check valve can be fully open or reduced in diameter, and its end connections are commonly flanged and clamped.

5. Flange

    The flange is a flange with bolt holes and is used to connect the end connection of the sealing structure of the pressure equipment. Flanges that comply with API specifications are API flanges. Blind flanges do not have a central through hole and are used to completely close the flange end face or outlet connection. The blind flange and the outlet flange to be closed should have the same pressure level and be equipped with the same sealing elements.

     According to different connection methods, flanges can be divided into threaded flanges and welded neck flanges. One side of the threaded flange is the sealing surface, and the other side is the internal thread. One side of the welding neck flange is the sealing surface, and the other side is the welding groove.

6. Gasket ring

     The gasket ring is a sealing element for flange connection. Commonly used API steel rings are R type, RX type and BX type. R type and RX type steel ring can be used interchangeably in 6B type flange. BX type steel ring can only be used for 6BX type flange. RX type and BX type steel ring have pressure self-tightening performance, but they are not interchangeable.

    The surface roughness of all 23° of R type and RX type steel ring shall not be lower than 63RMS, and all 23° of BX type steel ring

The surface roughness should not be lower than 32RMS. Type RX and BX steel rings have a pressure through hole, drilled through the entire height of the steel ring.

7. Bolts and nuts

  Bolts and nuts are components used to connect flanges and clamps. The threads of bolts and nuts shall comply with API Std 5B.

8. Back pressure valve (back pressure valve)

    The back pressure valve is installed in the tubing hanger. When removing the blowout preventer or installing and disassembling the Christmas tree, a back pressure valve is required to seal the inner hole of the tubing; when the lower main valve is repaired and replaced, back pressure is also required The valve seals the inner hole of the oil pipe. There are generally two types of back pressure valves, one is fixed by threads, and the other is fixed by an expansion locking mechanism.

9. Christmas tree cap

   The Christmas tree cap is installed on the wax removal valve on the top of the Christmas tree, and is used to provide a quick vertical entrance into the tubing space. If you want to perform wire rope operations, coiled tubing operations, production testing, switch sliding sleeves, loading and unloading back pressure valves, etc., you must first remove the Christmas tree cap.

10. Christmas tree valve

The main valve controls the main passage of oil and air flow into the Christmas tree.

The production gate controls the flow of oil to the oil outlet pipeline.

The wax removal gate can be connected to the wax removal blowout prevention pipe.

The choke controls the output of the spouting well.

Small cross, connecting parts.





Wellhead or Christmas Tree? What's the difference?

The words Christmas Tree and Wellhead are often used interchangeably in the oil and gas industry. However, a wellhead and a Christmas tree are entirely separate equipment. They are both vital to gas and oil production, and they each have valves and other equipment that aids in controlling and guiding the flow of materials. 


A wellhead is necessary to control the pressure during drilling and production. It is located on the surface of the well between the casing and the drilling floor, allowing safe and controlled access to a live well. The wellhead suspends the casing and provides pressure seals for the casing string. It supports the BOP (Blowout Preventer) during drilling, the FRAC Tree during completion, and a Production Christmas Tree after completion. The wellhead is present during the drilling, completion, and production phases.

 

The Christmas Tree's primary purpose is to control the flow of resources—typically oil or gas—into and out of a well during production. The Christmas tree arrives and is attached to the wellhead after finalizing the drilling process. The Christmas Tree is a series of valves, spools, gauges, and chokes. 

A total of five valves are included in a Christmas tree, and each one is designed for a specific function.

Kill Wing Valve: This valve injects fluids like drilling mud or brine into the well to control pressure. It is often used during well interventions and maintenance activities to "kill" the well, meaning to control the pressure and halt the flow of fluids.

Swab Valve: The swab valve is located at the top of the Christmas tree and provides access to the well for a wireline or coiled tubing operation. This allows for well interventions, maintenance, or logging without needing to kill the well. It plays a crucial role in maintenance and troubleshooting operations.

Production Wing Valve: This valve controls the flow of oil and gas from the well to the production facilities. It can be opened or closed to start or stop production, and it's also used to regulate the flow rate to optimize production or manage potential issues like sand production.

Upper Master Valve: The upper master valve is one of the primary isolation valves, which can completely shut off the well's flow. It's typically used in emergency situations to quickly and effectively halt the flow of oil and gas, providing a critical layer of safety and environmental protection.

Lower Master Valve: The lower master valve is another primary isolation valve with functionality similar to the upper master valve. It provides redundancy, ensuring a backup is available to shut off the well if the upper master valve fails for some reason. Having both an upper and lower master valve gives operators more flexibility and enhances safety measures. 
 
Together these components regulate pressure, control flow, and allow access to the wellbore during the completion and production stages of the well. It is named for its resemblance to a decorated tree at Christmas. This vital piece of equipment assists in numerous ways well intervention, pressure relief, chemical injection, well-monitoring, flow composition and rate, valve, choke position feedback, and more. 


How are S-Seals and FS-Seals used for Wellheads and Christmas Trees?

CDI manufactures precision-molded S and FS Seals that employ anti-extrusion springs required for high pressures and a broad range of temperatures. S and FS Seals offer maximum extrusion resistance in demanding high-pressure, high-temperature (HPHT) sealing environments. Our S-Seal is well-known as a technologically advanced replacement for traditional three-piece T-Seals or O-Rings with back-ups. A metal garter spring is incorporated into a uniquely designed elastomeric seal element. This enables it to withstand large extrusion gaps (up to .125"). Our FS-Seal is a replacement for S-Seals in applications with large extrusion gaps or where equipment diameters may be inconsistent. The FS-Seal incorporates metal garter springs with a uniquely designed elastomeric seal element. This design is capable of sealing areas where a high degree of seal deflection is necessary to compensate for variations in piping, casing, or large-diameter parts. An FS seal is an ID seal with a thicker cross-section, and they are used for significant extrusion gaps and rougher casing surfaces. 

CDI manufactures high-quality custom and industry standard sizes of S and FS seals in NBR, HNBR, and FKM materials to meet our client's unique sealing requirements and quickly supply them throughout their business cycle.

       The tubing head cross is the main structure of the tubing head. The bottom of the tubing head cross is connected to the casing head, the top is connected to the Christmas tree, and the top and bottom are sealed with steel rings. The tubing head cross provides a carrier and container for the tubing hanger.

      The tubing head spool is used to perform positive and reverse circulation well flushing to observe the casing pressure, and to perform various operations through the annular space of the oil jacket.

3). Tubing top wire

    After the oil pipe hanger is installed in place, the oil pipe hanger wire must be installed. The function of the tubing hanger wire is to lock the tubing hanger and prevent it from moving up and down and rotating.

3). Top wire flange

      The jack flange is mounted on the casing cross, and the tubing is hung on the seat of the jack flange, and plays the role of squeezing the packing and sealing the annular space of the oil jacket. At the same time, it jams the tubing to prevent excessive pressure in the well. Eject the tubing string when it is high.

X-Mass

Christmas tree concept

     Christmas trees are wellhead devices used to extract oil from blowout wells and mechanical production wells. It is the main equipment for controlling and regulating oil and gas production at the top of oil and gas wells. The Christmas tree is composed of valves, reducers, nozzles and pipe fittings. It is used to control production and repair steel wires, cables, coiled tubing, etc. A device that provides conditions for well operations.

The role of Christmas tree

(1) Connect each layer of casing downhole, seal the annular space of each layer of casing, and bear part of the weight of the casing.

(2) Suspending tubing and downhole tools, supporting the weight of all tubing strings in the well, and sealing the annular space between tubing and casing.

(3) Control and regulate the production of oil wells.

(4) Ensure the construction of various underground operations, facilitate the construction of well killing operations, starting operations and other measures, and carry out daily production management such as pressure measurement and wax removal.

(5) Record oil pressure and casing pressure data.


Christmas tree classification

  According to the structure of the Christmas tree, it can be divided into two types: split type and integral type. Split type is assembled by some independent parts such as valves.

The integral type is to make the main valve, safety valve, wax removal valve and wing valve into an integral part. The distance between the valve and the valve is small, which saves space and is resistant to high pressure. It is especially suitable for oil and gas wells on offshore platforms.

According to the types of production wells and well completion production methods, they can be divided into self-blowing wells, electric submersible pump wells, gas lift wells, screw pump wells, water injection wells, and Christmas trees for gas wells.

Single tube and double tube

1. Single Tubing Christmas Tree

    The single-tubing Christmas tree is installed on the wellhead of a single-tubing completion. In addition to the split type and the integral type, it also has a single wing and a double wing. Depending on the type of well or the production method of the well, valves and pup joints can be combined into different forms of single tubing Christmas tree, and the connection method can be flange type, thread type or clamp type.

2. Double tubing Christmas tree

    The double-tubing Christmas tree is installed on the wellhead of the double-tubing completion, and is used for the production control of the simultaneous and independent exploitation of two oil layers. The dual tubing completion is to run two parallel tubing strings (long tubing string and short tubing string) or two concentric tubing strings in the same production casing, and pair the two tubing strings through a dual-tube packer and a single-tube packer. Separate oil (or gas) intervals.

3. Three-tube Christmas tree

      With the development of technology and actual application requirements on site, three-tube Christmas trees have appeared.

Christmas tree related parts

1. Tubing cross and tee

    The tubing four-way and three-way of the Christmas tree are connected with the main valve, wax removal valve and wing valve. The common four-way and three-way are flanged and flange-studded. The Christmas tree with four links is a double-wing Christmas tree, and the Christmas tree with three links is a single-wing Christmas tree. On some platforms, the three-way Christmas tree is composed of a wax removal valve and a main valve or a wellhead safety valve, which becomes an integral Christmas tree.

2. Gate valve and plug valve

    The gate valve is a valve in which the moving direction of the closing part (gate) is perpendicular to the flow direction. A plug valve is a valve that shuts off the rotation of a component (cock), and the plug can be cylindrical, conical or spherical. Play the role of wellhead control.

3. Grease nipple

    The nozzle is a component used to control the flow of the oil well on the Christmas tree. It is installed between the wing valve and the oil outlet pipeline. The nozzle can also be used to control the gas injection volume of gas lift wells and the water injection volume of water injection wells. The nozzle is a throttling element. The reasonable production pressure difference of the oil well can be controlled by changing nozzles with different hole diameters. The nozzle is made of high-carbon alloy steel after heat treatment. There are many kinds of hole diameter from 2-20mm, each difference of 0.5mm is a grade.

   There are two types of nozzles: fixed and adjustable. The fixed nozzle is equipped with replaceable parts. This part has a fixed hole for throttling. The adjustable nozzle has a small hole of variable area controlled by the outside and a corresponding small hole area indicating mechanism. The orifice of the oil nozzle is a small hole distributed on the tubular part, and the change in the number of the small holes covered by the outer sleeve of the tubular part is the change in the flow area.

4. Check valve

     A check valve is a valve that only allows fluid to flow freely in one direction, so it is also called a check valve. The check valve has a mechanism that automatically prevents fluid from flowing in other directions. The check valve on the Christmas tree is generally installed between the wing valve and the nozzle. There is no check valve installed on the Christmas tree in some oil wells, but a check valve is generally installed on the Christmas tree in the water injection well. The check valve has oil outlet pipe type, swing open type, rising rod type and butterfly type. The check valve can be fully open or reduced in diameter, and its end connections are commonly flanged and clamped.

5. Flange

    The flange is a flange with bolt holes and is used to connect the end connection of the sealing structure of the pressure equipment. Flanges that comply with API specifications are API flanges. Blind flanges do not have a central through hole and are used to completely close the flange end face or outlet connection. The blind flange and the outlet flange to be closed should have the same pressure level and be equipped with the same sealing elements.

     According to different connection methods, flanges can be divided into threaded flanges and welded neck flanges. One side of the threaded flange is the sealing surface, and the other side is the internal thread. One side of the welding neck flange is the sealing surface, and the other side is the welding groove.

6. Gasket ring

     The gasket ring is a sealing element for flange connection. Commonly used API steel rings are R type, RX type and BX type. R type and RX type steel ring can be used interchangeably in 6B type flange. BX type steel ring can only be used for 6BX type flange. RX type and BX type steel ring have pressure self-tightening performance, but they are not interchangeable.

    The surface roughness of all 23° of R type and RX type steel ring shall not be lower than 63RMS, and all 23° of BX type steel ring

The surface roughness should not be lower than 32RMS. Type RX and BX steel rings have a pressure through hole, drilled through the entire height of the steel ring.

7. Bolts and nuts

  Bolts and nuts are components used to connect flanges and clamps. The threads of bolts and nuts shall comply with API Std 5B.

8. Back pressure valve (back pressure valve)

    The back pressure valve is installed in the tubing hanger. When removing the blowout preventer or installing and disassembling the Christmas tree, a back pressure valve is required to seal the inner hole of the tubing; when the lower main valve is repaired and replaced, back pressure is also required The valve seals the inner hole of the oil pipe. There are generally two types of back pressure valves, one is fixed by threads, and the other is fixed by an expansion locking mechanism.

9. Christmas tree cap

   The Christmas tree cap is installed on the wax removal valve on the top of the Christmas tree, and is used to provide a quick vertical entrance into the tubing space. If you want to perform wire rope operations, coiled tubing operations, production testing, switch sliding sleeves, loading and unloading back pressure valves, etc., you must first remove the Christmas tree cap.

10. Christmas tree valve

The main valve controls the main passage of oil and air flow into the Christmas tree.

The production gate controls the flow of oil to the oil outlet pipeline.

The wax removal gate can be connected to the wax removal blowout prevention pipe.

The choke controls the output of the spouting well.

Small cross, connecting parts.





Wellhead or Christmas Tree? What's the difference?

The words Christmas Tree and Wellhead are often used interchangeably in the oil and gas industry. However, a wellhead and a Christmas tree are entirely separate equipment. They are both vital to gas and oil production, and they each have valves and other equipment that aids in controlling and guiding the flow of materials. 


A wellhead is necessary to control the pressure during drilling and production. It is located on the surface of the well between the casing and the drilling floor, allowing safe and controlled access to a live well. The wellhead suspends the casing and provides pressure seals for the casing string. It supports the BOP (Blowout Preventer) during drilling, the FRAC Tree during completion, and a Production Christmas Tree after completion. The wellhead is present during the drilling, completion, and production phases.

 

The Christmas Tree's primary purpose is to control the flow of resources—typically oil or gas—into and out of a well during production. The Christmas tree arrives and is attached to the wellhead after finalizing the drilling process. The Christmas Tree is a series of valves, spools, gauges, and chokes. 

A total of five valves are included in a Christmas tree, and each one is designed for a specific function.

Kill Wing Valve: This valve injects fluids like drilling mud or brine into the well to control pressure. It is often used during well interventions and maintenance activities to "kill" the well, meaning to control the pressure and halt the flow of fluids.

Swab Valve: The swab valve is located at the top of the Christmas tree and provides access to the well for a wireline or coiled tubing operation. This allows for well interventions, maintenance, or logging without needing to kill the well. It plays a crucial role in maintenance and troubleshooting operations.

Production Wing Valve: This valve controls the flow of oil and gas from the well to the production facilities. It can be opened or closed to start or stop production, and it's also used to regulate the flow rate to optimize production or manage potential issues like sand production.

Upper Master Valve: The upper master valve is one of the primary isolation valves, which can completely shut off the well's flow. It's typically used in emergency situations to quickly and effectively halt the flow of oil and gas, providing a critical layer of safety and environmental protection.

Lower Master Valve: The lower master valve is another primary isolation valve with functionality similar to the upper master valve. It provides redundancy, ensuring a backup is available to shut off the well if the upper master valve fails for some reason. Having both an upper and lower master valve gives operators more flexibility and enhances safety measures. 
 
Together these components regulate pressure, control flow, and allow access to the wellbore during the completion and production stages of the well. It is named for its resemblance to a decorated tree at Christmas. This vital piece of equipment assists in numerous ways well intervention, pressure relief, chemical injection, well-monitoring, flow composition and rate, valve, choke position feedback, and more. 


How are S-Seals and FS-Seals used for Wellheads and Christmas Trees?

CDI manufactures precision-molded S and FS Seals that employ anti-extrusion springs required for high pressures and a broad range of temperatures. S and FS Seals offer maximum extrusion resistance in demanding high-pressure, high-temperature (HPHT) sealing environments. Our S-Seal is well-known as a technologically advanced replacement for traditional three-piece T-Seals or O-Rings with back-ups. A metal garter spring is incorporated into a uniquely designed elastomeric seal element. This enables it to withstand large extrusion gaps (up to .125"). Our FS-Seal is a replacement for S-Seals in applications with large extrusion gaps or where equipment diameters may be inconsistent. The FS-Seal incorporates metal garter springs with a uniquely designed elastomeric seal element. This design is capable of sealing areas where a high degree of seal deflection is necessary to compensate for variations in piping, casing, or large-diameter parts. An FS seal is an ID seal with a thicker cross-section, and they are used for significant extrusion gaps and rougher casing surfaces. 

CDI manufactures high-quality custom and industry standard sizes of S and FS seals in NBR, HNBR, and FKM materials to meet our client's unique sealing requirements and quickly supply them throughout their business cycle.

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