What Tests Are Performed On The Wellhead And Xmas-Tree?
Advances in technology and procedures in flow assurance and wellbore management result in extended field lifeline and efficient utilization of resources in oil and gas production.
To safeguard structural integrity, you have to adequately service and maintain the wellhead and Christmas tree to confirm the good integrity is fit for its purpose.
Additionally, servicing and maintaining wellhead and Xmas-Tree ensures a reliable surface barrier against hydrocarbon leakage during emergencies.
Continuous high-quality and efficient production of oil and gas can lead to complacency concerning the integrity of wellhead and Xmas-Tree or a lack of routine test and maintenance.
That is why it is essential to carry out wellhead and Xmas-Tree tests frequently and at different levels to ensure well integrity and efficient production.
Lack of this is likely to expose elements to mechanical failure and production downtime.
Common mechanical failures in wellhead and Xmas-Tree
The structural integrity of a wellhead and Xmas-Tree depends on various external factors and conditions and can lead to mechanical failures.
When conducting wellhead and Xmas-Tree tests, these are often the most common failure mechanisms that you will find.
- Failure in mechanical assemblies;
- Corrosion & Erosion;
- Seals & Gaskets failure;
- Missing Components;
- Formation Changes;
- Failures are due to changes to Company Policies or Technology.
Wellhead and Xmas-Tree test and maintenance
To ensure that wellhead and Xmas-Tree maintenance follows a structured approach, you have to plan sufficiently before executing the test and maintenance program.
As much this may not be possible all the time, every effort you put in it helps to minimize the time spend and damage caused by ensuring wellhead integrity.
The first thing you need to do is to conduct a field survey.
This stage provides you with an opportunity to accurately list the wellhead and Xmas-Tree manufacturer, specifications, and operating features of the well.
Put down this information to form the basis of the wellhead and Xmas-Tree test, giving you full traceability of everything you do.
The field survey is essentially the first opportunity to identify the critical condition of the wellhead and Xmas-Tree.
After doing this, it is essential to draw a report of everything you have identified through visual inspection of various wellhead and tree components.
Onsite wellhead and Xmas-Tree tests
Onsite tests for wellhead and tree component is carried out. This involves physical inspection for faults.
This procedure is carried out without removing any element from the wellhead.
The wellhead and Xmas-Tree chemical property test follows the wellhead and Xmas-Tree physical property test.
Bleeding off pressure from the annulus or flushing a stuck valve can be done at this stage.
If there is any fault at this moment, replacements may be required.
However, it is sporadic to find failure at this phase of the test.
In most cases, manufacturer components and assemblies are not always seen with physical or chemical faults.
Another test that can be done onsite is the wellhead pressure test.
This is done in three phases.
The first one is the onshore wellhead pressure test, where wellhead and tree components are tested for functionality integrity before and after installation.
Wellhead offshore pressure test is done for the same reason.
In both instances, casing and liners are tested to verify if they can withstand various pressure conditions from within and without.
The last bit of pressure test is done using slip and seal assembly.
When a slip and seal assembly is used to hang off the casing, the joint ring cavity is put on pressure test at utmost 50% of the least collapse value as indicated in the table below:
|Pressure test||Least collapse value|
|13.8/8 inches casing||1000||1950 psi|
|9.5/8 inches casing||2500||4750 psi|
|7 inches casing||3000||7020 psi|
It is advisable not to go beyond 3000 psi for the 7 inches slip and seal assembly.
Accordingly, the duration for every pressure test should be at most 15 minutes for a stabilized pressure. All BOP nad surface equipment are pressure tested to 5000 psi using a plug-type tester.
Off-site wellhead and Xmas-Tree tests
Off-site wellhead and Xmas-Tree tests are done in production facilities.
The first test done is a dimensional inspection on wellhead and tree components to ensure they API standards.
BOP and well control equipment is used to manage the high-risk part of oil and gas production, and they represent the most vital components of any wellbore.
Therefore, there is a need for meticulous inspection and detailed reporting on these components and integrated systems to ensure well integrity.
The dimension inspection should encompass all risk assessment and surveillance activities in the lifeline of the equipment.
The evaluation should be based on API S53 benchmark, and it should include regulatory compliance,
If the wellhead and tree components are qualified, they are passed to the subsequent process in the production cycle. On the other hand, if they fail the dimensional test, they are replaced.
The pressure test and seal test are carried out before the wellhead, and Xmas-Tree components are transported to the wellbore site.
However, these tests are also done at the site with the prevailing well conditions.
It is crucial to ensure that well equipment is suitable for the pressure and temperature conditions of the well and that can only be done at the site.
Once the critical test activities are completed, plans for regular maintenance inspections and ensuring the integrity of the wellhead and Xmas-Tree are made.
This activity is done on a rotational basis.
The wellhead and Xmas-Tree operator must comply with the acceptable operating limits for every wellhead and Xmas-Tree variable.
The following are some of the variables:
- Wellhead and Xmas-Tree gate valves functional tests;
- Tubing hanger and casing hanger pressure tests;
- Tree valves pressure tests;
- Actuator closure times and function testing;
Careful planning and structured execution of wellhead and Xmas-Tree maintenance and tests are essential to ensuring well integrity.
At Sanjack Petro, we manufacture and distribute wellhead and Xmas-Tree equipment you can trust for efficient and high-quality oil and gas production.
We have more than 40 years of experience in ensuring our products meet regulatory and safety requirements.
Accordingly, our products are tested before reaching the market to make sure that they do not lead to wellbore failures.