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Subsea Christmas tree engineering: thermal, contact and structural analysis
Cool-down curves, thermal insulation, sealing and structure of wet Christmas trees and subsea equipment, with CFD++ and Adina. We find the limits of the design before testing and manufacturing.
Approved supplier of a global oilfield services company for subsea system analysis, after test cases of nonlinear FEA, contact and erosion CFD.
- Global supplier approvalApproved in the United States and in Brazil, with a long-term contract for subsea system simulations.
- Insulation approvedA new, lighter insulation material for subsea lines was approved with the help of ATS.
- Seal checked beyond its designA valve seal met the allowed internal leakage for up to 3 cycles at a condition much higher than the design one.
- Collapse method approved with testsCollapse pressure of a deep-water pipeline for three load and clamp configurations.
- Test sized in the labThermal analysis of a test flange showed the target temperature was not exceeded.
Complete solutions, from the thermal curve to the structure
We prefer whole projects to isolated simulations: ATS responsible for thermal, contact and structural analyses, and the report.
Thermal and structure together
The same equipment is checked for cool-down time and for stresses and sealing, so one finding does not hide the other.
Insulation design
Material, thickness, shape and installation places of the insulation are studied to delay the cool-down.
Before the test
Models define the limits of the equipment and help size the tests, which saves tests and manufacturing.
Need only a part? We define the scope with you.
What you receive
Cool-down curve
Temperature at several points of the tree from the shutdown of the hot flow, in steady-state and transient.
Insulation design
Material, thickness, shape and locations, optimized with iChrome Nexus coupled to FEA or CFD.
Contact and sealing analysis
Seal seats and O-rings, with elastic and plastic deformation, and the allowed internal leakage.
Hyperelastic materials
Contact analysis of hyperelastic plugs for different pressures, sizes, materials and thicknesses, with the pre-stress confirmed by tests.
Pipeline collapse
Collapse pressure for different load and clamp configurations, with the nonlinear solver.
Test planning
Thermal checks of test setups, for example that a flange stays below a target temperature during a tensile test.
The Christmas tree and why it cools
What it is
The Christmas tree is a set of remotely operated valves installed on the wellhead. It controls the production of the well in an intelligent, optimized way, with no need for maintenance, and measures the pressure and temperature of the well and its lines. The lines can be production or injection lines.
In Brazil, wet Christmas trees are the most common because of offshore production. The name comes from the dry type in cold regions of the USA, which after snow looked like a pine tree.
How it works in the pre-salt
In the pre-salt, trees work at great depth, below 2000 m, with high external pressure and an average temperature of 4 °C. They can pump 5,000 to 15,000 barrels of oil per day. A 5,000 psi tree weighs 86 tons and is about 7 meters tall.
A typical wet tree has a production master valve, a production side valve, a production and ring interlock valve, a master ring valve and a side valve.
Cool-down and paraffins
If the extraction stops, the lines and the tree cool to the temperature of the ocean, 4 °C, since the hot flow no longer runs through the pipeline. The oil must flow above 40 °C because of paraffins, which solidify at lower temperatures and block the flow.
An important study is the cooling curve at several points of the tree from the shutdown. The tree has thermal insulation to delay it, and the material, thickness, shape and installation places need to be studied to optimize the design.
How we analyze it
The thermal analysis is done with CFD++ or with the advanced thermal modules of FEA (Adina Thermal), which calculate the transient not only in solids but also in liquids. iChrome Nexus saves time and designs the insulation coupled with FEA or CFD.
ATS has done designs and simulations of steady-state and transient thermal analysis for subsea systems, for oilfield services and subsea engineering companies, including an R&D project for an operator.
Tools, and where each one fits
Tools serve the engineering work. We say what each one does in the project.
| Tool | Role in the project | Status |
|---|---|---|
| CFD++ | Fluid flow, heat transfer, combustion and particles in 3D. ATS is the exclusive CFD++ representative in Brazil. | Licensed |
| Adina | Thermal in solids and liquids, nonlinear structures, contact and hyperelastic materials. | Licensed |
| Femap, NX Nastran, Adina | Stress analysis, contact, hyperelastic and nonlinear materials, thermal and fluid-structure coupling. | Licensed |
| iChrome Nexus | Optimizer and manager of complex CAD, CFD and FEA workflows. | Licensed |
| Python, Nsp, Scilab | Analytical and control models, and optimization, with no license needed. | In use |
Evidence you can check
Work for oilfield services and subsea engineering companies.
Project work
| Project | What we did | Tools and tests | Result or venue |
|---|---|---|---|
| Thermal analysis of underwater equipmentProject | Make sure the flange of a component submitted to a tensile test would not exceed a target temperature. | Thermal CFD with natural convection, radiation and conduction, for two flange geometries. | Target temperature not exceeded. The client ran the test with no problems. |
| Contact analysis of a valve sealProject | Study of a valve seal subjected to an operating condition much higher than the design one. | Nonlinear FEA with elastic and plastic deformation. | Seal seat met the allowed internal leakage for up to 3 operation cycles. Deformed geometry predicted after the 3 cycles. |
| Pipeline collapseProject | Collapse of a pipeline used in deep-water operation. | Three cases in the advanced nonlinear solver, which handles plastic deformation of the material. | Collapse pressure for three load and clamp configurations. Method approved with test data. |
| Duct plugProject | Sealing of a duct plug under different pressures, duct size, material and thickness. | Hyperelastic material and contact analysis. Study of material test standards. | Plug tested analytically with no expensive testing. Pre-stress confirmed by tests. Limits of the equipment understood. |
| Oceaneering and Shell: heating of a subsea lineProject | Transient thermal analysis of a heating system to remedy the flow in ducts on the seabed, below 2000 m. | Steady-state CFD++, analytical model and PID control. See the subsea systems page. | Operator approved the result. The client sized the lab test with ATS design recommendations. |
How an engagement runs
Diagnosis and goal
We define the problem, the operating conditions and the target with your team.
Model
The geometry of the equipment is prepared and the physics that apply are chosen.
Analysis
Numerical calculation based on the applicable physical principles.
Checks and validation
Results are checked for consistency and compared with tests, plant data or the literature.
Solution and report
Design of the solution, specification of the test when needed, and the report.
Follow-up
Support in the field test or in operation, and revisions.
Related services
Questions engineers ask before they hire us
What do you calculate for a Christmas tree?
Mainly the cool-down curve at several points after the shutdown, the insulation design, and the contact, sealing and structure of valves and seals.
Why does the cool-down time matter?
The oil must flow above 40 °C. Below that, paraffins solidify and block the flow, so the time the tree takes to cool after a shutdown defines the response time of the operation.
Can you check a seal beyond its design condition?
Yes. In one case, a valve seal met the allowed internal leakage for up to 3 cycles at a condition much higher than the design one, and the deformed geometry was predicted.
Is our data kept confidential?
Yes. We work under NDA, and your design data and reports stay with you.
Tell us about the equipment and the condition
Send the equipment, the pressure and temperature, and the question you need answered.
sales@aerothermalsolutions.co+55 11 3854-4224An ATS engineer replies. We work under NDA.
Two ways to contract: by package, for a defined scope and number of cases, or by hour, for open scope. An hourly contract can become a package.