| name | neqsim-subsea-and-wells |
| description | Subsea production systems, well design, SURF cost estimation, and tieback analysis with NeqSim. USE WHEN: designing subsea fields, sizing flowlines and umbilicals, estimating well costs, performing casing design, running tieback comparisons, or configuring subsea equipment (trees, manifolds, boosters, risers). |
| last_verified | 2026-06-28 |
NeqSim Subsea & Wells Skill
Reference for subsea production system design, well mechanical design, SURF cost
estimation, and tieback analysis using NeqSim.
Subsea Development Architecture
A typical subsea development consists of:
Reservoir → Wells → Subsea Trees → Jumpers → Manifold → Flowlines → Riser → Host
↑
Umbilical (power, control, chemicals)
Equipment Classes in NeqSim
| Equipment | NeqSim Class | Package |
|---|
| Subsea well | SubseaWell | process.equipment.subsea |
| Christmas tree | SubseaTree | process.equipment.subsea |
| Manifold | SubseaManifold | process.equipment.subsea |
| Subsea booster | SubseaBooster | process.equipment.subsea |
| Jumper | SubseaJumper | process.equipment.subsea |
| Flowline | SimpleFlowLine | process.equipment.subsea |
| Flexible riser | FlexiblePipe | process.equipment.subsea |
| Steel/rigid riser | SimpleFlowLine | process.equipment.subsea |
| Umbilical | Umbilical | process.equipment.subsea |
| PLET | PLET | process.equipment.subsea |
| PLEM | PLEM | process.equipment.subsea |
| Floating production | FloatingSubstructure | process.equipment.subsea |
| Mooring | MooringSystem | process.equipment.subsea |
Well Design
Casing Design (API 5C3 / NORSOK D-010)
SubseaWell well = new SubseaWell("Producer-1", stream);
well.setWellType(SubseaWell.WellType.OIL_PRODUCER);
well.setCompletionType(SubseaWell.CompletionType.CASED_PERFORATED);
well.setRigType(SubseaWell.RigType.SEMI_SUBMERSIBLE);
well.setWellLocationType(WellCostEstimator.WellLocationType.SUBSEA_WET_TREE);
well.setMeasuredDepth(3800.0);
well.setTrueVerticalDepth(3200.0);
well.setWaterDepth(350.0);
well.setMaxWellheadPressure(345.0);
well.setReservoirPressure(400.0);
well.setConductorOD(30.0); well.setConductorDepth(100.0);
well.setSurfaceCasingOD(20.0); well.setSurfaceCasingDepth(800.0);
well.setIntermediateCasingOD(13.375); well.setIntermediateCasingDepth(2500.0);
well.setProductionCasingOD(9.625); well.setProductionCasingDepth(3800.0);
well.setTubingOD(5.5);
well.setTubingWeight(23.0);
well.setTubingGrade("L80");
well.setPrimaryBarrierElements(3);
well.setSecondaryBarrierElements(3);
well.setHasDHSV(true);
well.setDrillingDays(45.0);
well.setCompletionDays(25.0);
well.setRigDayRate(540000.0);
well.initMechanicalDesign();
WellMechanicalDesign design = (WellMechanicalDesign) well.getMechanicalDesign();
design.calcDesign();
design.calculateCostEstimate();
double burstDF = design.getProductionCasingBurstDF();
double collapseDF = design.getProductionCasingCollapseDF();
double tensionDF = design.getProductionCasingTensionDF();
boolean barrierOk = design.isBarrierVerificationPassed();
double totalCost = design.getTotalCostUSD();
String json = design.toJson();
Dry vs Wet Wells
Use WellCostEstimator.WellLocationType to distinguish subsea wet-tree wells
from platform dry-tree wells. The same flag is carried by SubseaWell and fed
into WellMechanicalDesign.calculateCostEstimate().
SubseaWell wetWell = new SubseaWell("Subsea producer", stream);
wetWell.setWellLocationType(WellCostEstimator.WellLocationType.SUBSEA_WET_TREE);
SubseaWell dryWell = new SubseaWell("Platform producer", stream);
dryWell.setWellLocationType(WellCostEstimator.WellLocationType.PLATFORM_DRY_TREE);
API 5CT Casing Grades
| Grade | SMYS (MPa) | Typical Use |
|---|
| H40 | 276 | Conductor |
| K55 | 379 | Surface casing |
| N80 / L80 | 552 | Intermediate casing, tubing |
| C90 | 621 | Sour service (H2S) |
| P110 | 758 | Production casing (high pressure) |
| Q125 | 862 | Ultra-deep / HP-HT |
NORSOK D-010 Design Factors
| Check | Minimum DF | Formula |
|---|
| Burst | 1.10 | DF = Burst_rating / (P_internal - P_external) |
| Collapse | 1.00 | DF = Collapse_rating / (P_external - P_internal) |
| Tension | 1.60 | DF = Yield_strength / Axial_load |
| Triaxial (VME) | 1.25 | Von Mises equivalent stress check |
SURF Cost Estimation
SURFCostEstimator
SURFCostEstimator surf = new SURFCostEstimator();
surf.setRegion(SubseaCostEstimator.Region.NORWAY);
surf.setNumberOfWells(4);
surf.setWaterDepthM(350.0);
surf.setTreePressureRatingPsi(10000);
surf.setTreeBoreSizeInches(6.0);
surf.setHorizontalTrees(true);
surf.setManifoldSlots(4);
surf.setNumberOfPLETs(2);
surf.setNumberOfPLEMs(1);
surf.setNumberOfJumpers(4);
surf.setJumperLengthM(30.0);
surf.setUmbilicalLengthKm(27.0);
surf.setUmbilicalHydraulicLines(8);
surf.setUmbilicalChemicalLines(2);
surf.setUmbilicalElectricalCables(2);
surf.setIncludeRisers(true);
surf.setFlexibleRiser(true);
surf.setRiserDiameterInches(12.0);
surf.setRiserLengthM(525.0);
surf.setInfieldFlowlineLengthKm(8.0);
surf.setExportPipelineLengthKm(25.0);
surf.setExportPipelineDiameterInches(12.0);
surf.calculate();
double surfCapex = surf.getTotalSURFCostUSD();
double subseaHardware = surf.getSubseaCostUSD();
double umbilicals = surf.getUmbilicalCostUSD();
double risers = surf.getRiserCostUSD();
double flowlines = surf.getFlowlineCostUSD();
List<Map<String, Object>> lineItems = surf.getLineItems();
Regional Cost Factors
| Region | Factor | Basis |
|---|
| Norway (NCS) | 1.0 | Reference |
| UK (UKCS) | 0.85-0.95 | Lower labor cost |
| Gulf of Mexico | 0.80-0.90 | Established supply chain |
| Brazil (pre-salt) | 1.10-1.30 | Deep water, local content |
| West Africa | 1.05-1.20 | Logistics premium |
Tieback Analysis
Workflow
- Define the satellite field (reservoir, fluid, wells)
- Define candidate host facilities with available capacity
- Configure tieback options (distance, diameter, insulation, boosting)
- Screen flow assurance (hydrate margin, arrival temperature, pressure drop)
- Estimate SURF CAPEX for each option
- Rank by NPV or unit technical cost
Usage
TiebackAnalyzer analyzer = new TiebackAnalyzer();
HostFacility host = new HostFacility("Platform Alpha");
host.setAvailableCapacity(30000.0);
host.setProcessingPressure(70.0);
host.setLocation(61.5, 2.5);
TiebackOption opt1 = new TiebackOption("Direct Tieback");
opt1.setFlowlineLength(15.0);
opt1.setFlowlineDiameter(10.0);
opt1.setWaterDepth(350.0);
opt1.setInsulationType("wet_insulation");
TiebackOption opt2 = new TiebackOption("Boosted Tieback");
opt2.setFlowlineLength(30.0);
opt2.setFlowlineDiameter(12.0);
opt2.setWaterDepth(450.0);
opt2.setHasBooster(true);
opt2.setBoosterType("multiphase_pump");
analyzer.setHost(host);
analyzer.addOption(opt1);
analyzer.addOption(opt2);
analyzer.setFluid(reservoirFluid);
TiebackReport report = analyzer.analyze();
Subsea System Configuration
Complete Subsea Layout
SubseaProductionSystem subseaSystem = new SubseaProductionSystem("Field Layout");
subseaSystem.setArchitecture(SubseaProductionSystem.SubseaArchitecture.MANIFOLD_CLUSTER);
subseaSystem.setWellCount(6);
subseaSystem.setManifoldCount(2);
subseaSystem.setWaterDepthM(400.0);
subseaSystem.setTiebackDistanceKm(30.0);
subseaSystem.setUmbilicalLengthKm(32.0);
subseaSystem.setFlowlineDiameterInches(12.0);
subseaSystem.setTubingDiameterInches(6.0);
subseaSystem.setCostRegion(SubseaCostEstimator.Region.NORWAY);
subseaSystem.setWellLocationType(WellCostEstimator.WellLocationType.SUBSEA_WET_TREE);
subseaSystem.setIncludeRisers(true);
subseaSystem.setFlexibleRiser(true);
subseaSystem.setProductionRiserCount(1);
subseaSystem.setReservoirDevelopmentCostMusd(25.0);
subseaSystem.setReservoirFluid(reservoirFluid);
subseaSystem.build();
subseaSystem.run();
int treeCount = subseaSystem.getTrees().size();
int jumperCount = subseaSystem.getJumpers().size();
int manifoldCount = subseaSystem.getManifolds().size();
int pletCount = subseaSystem.getPLETs().size();
int plemCount = subseaSystem.getPLEMs().size();
int umbilicalCount = subseaSystem.getUmbilicals().size();
int flexibleRiserCount = subseaSystem.getRisers().size();
int steelRiserCount = subseaSystem.getSteelRisers().size();
SubseaProductionSystem.SubseaSystemResult result = subseaSystem.getResult();
double surfCapexMusd = result.getTotalSubseaCapexMusd();
double wellsMusd = result.getWellCostMusd();
double reservoirMusd = result.getReservoirCostMusd();
double developmentCapexMusd = result.getTotalDevelopmentCapexMusd();
SubseaProductionSystem.build() creates the main process and design equipment:
SubseaWell, SubseaTree, SubseaJumper, SubseaManifold, PLET, PLEM,
SimpleFlowLine, Umbilical, and risers. With setFlexibleRiser(true) risers
are generated as FlexiblePipe; with setFlexibleRiser(false) steel/rigid
risers are generated as vertical SimpleFlowLine unit operations. All of these
classes expose mechanical design objects, and SURFCostEstimator includes trees,
manifolds, PLETs, PLEMs, jumpers, umbilicals, risers, flowlines, and pipelines in
the SURF CAPEX. The result separates SURF, well, reservoir, and total development
CAPEX.
Flowline and Pipeline Sizing
Steady-State Pipe Flow
PipeBeggsAndBrills pipeline = new PipeBeggsAndBrills("Export Line", feedStream);
pipeline.setLength(50000.0);
pipeline.setDiameter(0.508);
pipeline.setPipeWallRoughness(5e-5);
pipeline.setAngle(0.0);
pipeline.setNumberOfIncrements(50);
pipeline.setFormationTemperatureGradient(4.0, -0.03, "C");
pipeline.run();
double pressureDrop = feedStream.getPressure() - pipeline.getOutletPressure();
double arrivalTemp = pipeline.getOutletTemperature() - 273.15;
Pipeline Mechanical Design
AdiabaticPipe pipe = new AdiabaticPipe("Pipeline", feedStream);
pipe.setLength(50000.0);
pipe.setDiameter(0.508);
PipelineMechanicalDesign mechDesign =
(PipelineMechanicalDesign) pipe.getMechanicalDesign();
mechDesign.setMaxOperationPressure(150.0);
mechDesign.setMaterialGrade("X65");
mechDesign.setDesignStandardCode("DNV-OS-F101");
mechDesign.calcDesign();
double wallThickness = mechDesign.getWallThickness();
String report = mechDesign.toJson();
Flowline Cooldown and No-Touch Time
After a planned or unplanned shutdown, an insulated subsea flowline or riser
cools toward the seabed temperature. The no-touch time is how long operators
can wait before the fluid reaches the hydrate formation temperature (plus a
safety margin) and remedial action (depressurization, MEG/methanol injection) is
required. NeqSim couples a live fluid to a lumped cooldown engine with
SurfCooldownAnalyzer.
SurfCooldownAnalyzer analyzer = new SurfCooldownAnalyzer(fluid);
analyzer.setInternalDiameter(0.254);
analyzer.setWallThickness(0.0159);
analyzer.setInsulationThickness(0.060);
analyzer.setInsulationConductivity(0.17);
analyzer.setSeabedTemperature(4.0);
analyzer.setHydrateMargin(3.0);
analyzer.setRequiredNoTouchTimeHours(8.0);
analyzer.setOverallUValue(2.5);
analyzer.calculate();
double noTouch = analyzer.getNoTouchTimeHours();
String verdict = analyzer.getVerdict();
double hydrateTeqC = analyzer.getHydrateEquilibriumTemperatureK() - 273.15;
double tau = analyzer.getTimeConstantHours();
String json = analyzer.toJson();
How it works:
- Clones the fluid, runs
TPflash + initProperties, and reads getDensity("kg/m3")
and getCp("J/kgK") for the lumped thermal mass.
- Computes the hydrate equilibrium temperature via
hydrateFormationTemperature().
If the fluid has no free water (no hydrate risk), the verdict is NO_HYDRATE_RISK.
- Delegates the transient to
PipelineCooldownCalculator (exponential lumped
cooldown, layer or direct U-value). No-touch time is the time to reach
hydrateTeq + margin.
- Verdict bands: with a required no-touch time,
OK ≥ required, MARGINAL ≥ 0.75×,
else CRITICAL. Without one, OK ≥ 12 h, MARGINAL ≥ 6 h, else CRITICAL.
Standards: DNV-RP-F109 (cooldown / no-touch time basis), API RP 17A
(subsea system thermal management). Screening-level lumped model — use a
distributed transient thermal-hydraulic tool for detailed design.
package: neqsim.pvtsimulation.flowassurance —
SurfCooldownAnalyzer, PipelineCooldownCalculator.
Artificial Lift Screening
ArtificialLiftScreener alScreener = new ArtificialLiftScreener();
alScreener.setReservoirPressure(250.0);
alScreener.setWaterDepth(350.0);
alScreener.setGOR(200.0);
alScreener.setWaterCut(0.30);
alScreener.setDepth(3000.0);
alScreener.setProductionRate(5000.0);
Map<String, String> recommendations = alScreener.screen();
Gas Lift Design
GasLiftCalculator gasLift = new GasLiftCalculator();
gasLift.setWellDepth(3000.0);
gasLift.setReservoirPressure(250.0);
gasLift.setProductionRate(5000.0);
gasLift.setGLR(500.0);
gasLift.setInjectionPressure(150.0);
double optimalGLR = gasLift.calculateOptimalGLR();
double injectionRate = gasLift.calculateInjectionRate();
GasLiftOptimizer optimizer = new GasLiftOptimizer();
optimizer.addWell(well1, gasLift1);
optimizer.addWell(well2, gasLift2);
optimizer.setTotalGasAvailable(500000.0);
Map<String, Double> allocation = optimizer.optimize();
For a choke-back / open-up decision across a well fleet under multiple shared
facility ceilings (gas handling + produced-water/PWRI + lift-gas budget) with discrete
on/off locks, use ChokeAndGasLiftAllocationOptimizer + StrupeOkeReport
(neqsim.process.fielddevelopment.integrated). Build each well's response with
GasLiftPerformanceCurve.fromWellSystem(...). See the neqsim-production-optimization
skill for the full pattern.
Design Standards Reference
| Domain | Standard | Used For |
|---|
| Casing design | API 5CT / ISO 11960 | Casing/tubing grades, SMYS |
| Casing formulas | API Bull 5C3 / TR 5C3 | Burst, collapse, tension |
| Well barriers | NORSOK D-010 | Design factors, two-barrier principle |
| Submarine pipelines | DNV-ST-F101 | Wall thickness, on-bottom stability |
| Process piping | ASME B31.3 | Onshore/topsides piping |
| Pressure vessels | ASME VIII Div.1/2 | Separator, vessel sizing |
| Subsea production | API 17A-17Q | Subsea equipment specs |
| Risers | API 2RD / DNV-OS-F201 | Riser design |
| Flowlines | DNV-RP-F105 | Free-spanning pipelines |
| Fatigue | DNV-RP-C203 | S-N curves, fatigue life |
Common Subsea Design Pitfalls
| Pitfall | Impact | Prevention |
|---|
| Ignoring hydrate sub-cooling margin | Hydrate blockage | Design for 3-6°C subcooling below hydrate T |
| Undersized flowline (low rate sensitivity) | Cannot achieve design rate | Size for peak + 20% surge capacity |
| Missing umbilical in cost estimate | 10-15% CAPEX underestimate | Always include umbilical with routing factor 1.1× |
| Wrong water depth for cost curve | Non-physical costs | Verify depth matches field data |
| Ignoring slugging in riser | Separator flooding, trips | Include slug catcher sizing, check riser stability |
| No pipeline end expansion | Structural failure | Account for thermal expansion, expansion loops |
