General Knowledge of Wellhead and Tree

[Audio] Welcome everyone to this course on General Knowledge of Wellhead and Tree. In this video, we will touch on the basic knowledge of wellhead and tree, the industry standard around it and a very general idea of what is a wellhead and tree. After the video, we hope that you will have some basic knowledge and understanding of the products that we are supplying to our customers..

[Audio] As you can see from the screen, these will be the topics covered in the video today..

[Audio] First of all, what you are seeing on the screen are two main broad category of oil rig. A onshore rig which is on land and a offshore rig in the sea. This is where our wellhead and tree goes to for the extraction of oil and gas..

[Audio] In this slide, you will see how our wellhead is supporting the different casing string and the tubing string. For each of the casing string going into the earth, the weight is supported by either our mandrel hangers or slip hangers..

[Audio] Next, let me bring you to a overview of A P I 6 A. A P I 6 A is the governing industry standard of our wellhead and tree. It is the industry standard that gives recommendations for the performance, dimensional and functional interchangeability, design, materials, testing, inspection, welding, marking, handling , storing, shipment and purchasing of wellhead and tree equipment. As you can see in the slide, A P I 6 A comprises of many sections to address the requirements of wellhead and tree. Example, Section 5 provide guidelines to engineers when designing equipment and Section 10 touch on the requirements for testing of the equipment to ensure quality control standards listed in A P I 6 A are met..

[Audio] In this slide, we have more sections of A P I 6 A listed down. Whenever there are doubts on any of the wellhead and tree equipment from design to testing to shipment, we can always go to A P I 6 A to clear out any doubts. Do take the time to go through the different section listed in this video for an overall view..

[Audio] Now, we will go into a rough explanation of what is a wellhead. A wellhead is all permanent equipment between the uppermost portion of the surface casing and the tubing head adapter connector. It is made up of both pressure containing and pressure controlling equipment. The primary function of a wellhead is to Regulate and monitor the extraction of oil/ gas from the underground formation. Prevent the oil/gas from the underground formation from escaping into the atmosphere – Pressure containing equipment i.e. casing heads, casing/tubing spools 3. To suspend the casing/tubing strings.

[Audio] To Illustrate on what makes up a wellhead, please take a look at the above pictorial. On the extreme left of the slide, it is a schematic taken out from A P I 6 A, it shows the different components that made up a wellhead, likewise for our equipment. In the center of our slide, it is the conventional wellhead and on the extreme right, it is our unitized wellheads. Regardless of whether it is a conventional wellhead or a unitized wellhead, the main components that makes up a wellhead does not change..

[Audio] In this slide, you can compare the components of the conventional wellhead and unitized wellhead. A typical conventional wellhead will always comprise of a casing head / casing spool / tubing spool. A unitized wellhead is actually combining the conventional heads and spools into one piece of equipment. In a conventional wellhead, we have casing slip hangers whereas in the unitized wellhead, the equivalent is mandrel hangers. In a unitized system, we also have slip casing hangers but only used in stuck casing situations. Both kind of systems will have tubing hangers..

[Audio] From the overall view in the previous slide, we will zoom in to the different components of a wellhead, starting from the bottom most of the system. In a conventional system, right at the bottom is a casing head housing. It is a pressure containing piece of equipment, attached to the uppermost end of the surface casing that serves to suspend and seal against the surface casing. In this case, it is call Plastic injection seals or in short, P seals All the typical features that can be found in a casing head housing can be seen in the pictorial on the right..

[Audio] Within a casing head housing, we will have casing slip hangers that is used to suspend the casing weight by gripping the pipe with wedge like members, commonly known as slips. For unitized wellhead, the mandrel casing hanger is the primary equipment for suspending the casing string. In case emergency situations like stuck casing, casing slip hangers will be used to suspend the casing instead. For drilling operation, sealing off the annulus is required, in the case the seals is part of the casing slip hanger as shown in the pictorial on the left. For the unitized system, the seals are on the packoff body as shown in the pictorial on the right. For conventional system, we have lockdown screws, accessible externally whereas for a unitized system, we have internal lock ring for pressure hold down purpose..

[Audio] On top of a Casing Head, we will have a casing spool. Likewise for the casing head, the casing head spool is also used to suspend and seal off a casing string, known as the intermediate casing..

[Audio] Tubing Spool is attached to the uppermost casing spool or smallest casing string that serves to suspend the tubing and to seal the annular space between the tubing and production casing..

[Audio] Regardless of conventional or unitized wellhead, the tubing hanger that is used to support a tubing string will be installed within the tubing spool or unitized wellhead. Some features typically found within a tubing hanger is as shown in the pictorial on the right..

[Audio] A tree, also commonly known as Christmas tree is an assembly of equipment, including tubing head adapters, valves, tees, crosses, top connectors and chokes attached to the uppermost connector of the tubing head, used to control well production. There are two kind of tree, stack tree and block tree. A stack tree is a series loose valves while a block tree combines the series of valves within one piece of equipment called a tree..

[Audio] All the features of a tree can be seen from the pictorial above for both the stack tree and block tree..