neqsim-subsea-and-wells

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.

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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

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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);

// Geometry
well.setMeasuredDepth(3800.0);
well.setTrueVerticalDepth(3200.0);
well.setWaterDepth(350.0);
well.setMaxWellheadPressure(345.0);
well.setReservoirPressure(400.0);

// Casing program
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");

// Barrier elements (NORSOK D-010 two-barrier principle)
well.setPrimaryBarrierElements(3);
well.setSecondaryBarrierElements(3);
well.setHasDHSV(true);

// Drilling schedule & costs
well.setDrillingDays(45.0);
well.setCompletionDays(25.0);
well.setRigDayRate(540000.0);

// Mechanical design
well.initMechanicalDesign();
WellMechanicalDesign design = (WellMechanicalDesign) well.getMechanicalDesign();
design.calcDesign();
design.calculateCostEstimate();

// Results
double burstDF = design.getProductionCasingBurstDF();     // >= 1.10
double collapseDF = design.getProductionCasingCollapseDF(); // >= 1.00
double tensionDF = design.getProductionCasingTensionDF();   // >= 1.60
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

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SURF Cost Estimation

SURFCostEstimator

SURFCostEstimator surf = new SURFCostEstimator();
surf.setRegion(SubseaCostEstimator.Region.NORWAY);
surf.setNumberOfWells(4);
surf.setWaterDepthM(350.0);          // m
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

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Tieback Analysis

Workflow

1. Define the satellite field (reservoir, fluid, wells)
2. Define candidate host facilities with available capacity
3. Configure tieback options (distance, diameter, insulation, boosting)
4. Screen flow assurance (hydrate margin, arrival temperature, pressure drop)
5. Estimate SURF CAPEX for each option
6. Rank by NPV or unit technical cost

Usage

TiebackAnalyzer analyzer = new TiebackAnalyzer();

// Define host
HostFacility host = new HostFacility("Platform Alpha");
host.setAvailableCapacity(30000.0);   // boe/d spare capacity
host.setProcessingPressure(70.0);     // bara
host.setLocation(61.5, 2.5);         // lat, lon

// Define options
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();
// report contains: pressure drop, arrival temperature, hydrate margin,
// SURF cost, NPV ranking, flow assurance verdict per option

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Subsea System Configuration

Complete Subsea Layout

SubseaProductionSystem subseaSystem = new SubseaProductionSystem("Field Layout");
subseaSystem.setArchitecture(SubseaProductionSystem.SubseaArchitecture.MANIFOLD_CLUSTER);
subseaSystem.setWellCount(6);
subseaSystem.setManifoldCount(2);          // 2 manifolds x 3 wells
subseaSystem.setWaterDepthM(400.0);
subseaSystem.setTiebackDistanceKm(30.0);   // km to host
subseaSystem.setUmbilicalLengthKm(32.0);   // slightly longer routing
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.

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Flowline and Pipeline Sizing

Steady-State Pipe Flow

// Beggs & Brill multiphase correlation
PipeBeggsAndBrills pipeline = new PipeBeggsAndBrills("Export Line", feedStream);
pipeline.setLength(50000.0);           // m
pipeline.setDiameter(0.508);           // m (20 inch)
pipeline.setPipeWallRoughness(5e-5);   // m
pipeline.setAngle(0.0);               // horizontal
pipeline.setNumberOfIncrements(50);

// With formation temperature gradient (subsea/buried)
pipeline.setFormationTemperatureGradient(4.0, -0.03, "C");
// 4°C at seabed, -0.03 °C/m depth gradient

pipeline.run();
double pressureDrop = feedStream.getPressure() - pipeline.getOutletPressure();
double arrivalTemp = pipeline.getOutletTemperature() - 273.15;  // °C

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();  // mm
String report = mechDesign.toJson();

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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.

// Live fluid carries composition; analyzer auto-extracts density, Cp, hydrate Teq
SurfCooldownAnalyzer analyzer = new SurfCooldownAnalyzer(fluid);  // SystemInterface
analyzer.setInternalDiameter(0.254);        // m
analyzer.setWallThickness(0.0159);          // m
analyzer.setInsulationThickness(0.060);     // m
analyzer.setInsulationConductivity(0.17);   // W/m·K (wet insulation, PP foam)
analyzer.setSeabedTemperature(4.0);         // °C
analyzer.setHydrateMargin(3.0);             // K above hydrate Teq
analyzer.setRequiredNoTouchTimeHours(8.0);  // operational target (optional)

// Either give an overall U-value directly, or let the layer model compute it:
analyzer.setOverallUValue(2.5);             // W/m²·K  (skip for layer calc)

analyzer.calculate();
double noTouch = analyzer.getNoTouchTimeHours();
String verdict = analyzer.getVerdict();     // OK / MARGINAL / CRITICAL / NO_HYDRATE_RISK
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.

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Artificial Lift Screening

ArtificialLiftScreener alScreener = new ArtificialLiftScreener();
alScreener.setReservoirPressure(250.0);     // bara
alScreener.setWaterDepth(350.0);
alScreener.setGOR(200.0);                   // Sm3/Sm3
alScreener.setWaterCut(0.30);
alScreener.setDepth(3000.0);                // m TVD
alScreener.setProductionRate(5000.0);       // boe/d

// Screen all methods
Map<String, String> recommendations = alScreener.screen();
// Returns: {"ESP": "RECOMMENDED", "Gas Lift": "FEASIBLE",
//           "Rod Pump": "NOT_RECOMMENDED", ...}

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Gas Lift Design

GasLiftCalculator gasLift = new GasLiftCalculator();
gasLift.setWellDepth(3000.0);
gasLift.setReservoirPressure(250.0);
gasLift.setProductionRate(5000.0);
gasLift.setGLR(500.0);                    // Sm3/Sm3
gasLift.setInjectionPressure(150.0);      // bara

double optimalGLR = gasLift.calculateOptimalGLR();
double injectionRate = gasLift.calculateInjectionRate();

// Multi-well gas lift optimization
GasLiftOptimizer optimizer = new GasLiftOptimizer();
optimizer.addWell(well1, gasLift1);
optimizer.addWell(well2, gasLift2);
optimizer.setTotalGasAvailable(500000.0);  // Sm3/d
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.

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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

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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