Well Mechanical Design

NeqSim provides a comprehensive well mechanical design system for subsea wells, covering casing/tubing design, well barrier verification, weight estimation, and drilling & completion cost estimation.

Overview

The well design system follows the same three-layer architecture used throughout NeqSim’s mechanical design framework:

SubseaWell (equipment)
└── WellMechanicalDesign (design orchestration)
    ├── WellDesignCalculator (casing/tubing engineering)
    └── WellCostEstimator (drilling & completion costs)

Applicable Standards

Standard Scope
NORSOK D-010 Well integrity, two-barrier principle, design factors
API 5CT / ISO 11960 Casing and tubing grades and properties
API Bull 5C3 Burst, collapse, and tension formulas
API RP 90 Annular casing pressure management

Minimum Design Factors (NORSOK D-010)

Load Case Minimum DF
Burst 1.10
Collapse 1.00
Tension 1.60
Triaxial (VME) 1.25

Quick Start

// 1. Create fluid and stream
SystemInterface fluid = new SystemSrkEos(273.15 + 80.0, 200.0);
fluid.addComponent("methane", 0.80);
fluid.addComponent("ethane", 0.10);
fluid.addComponent("propane", 0.05);
fluid.setMixingRule("classic");

Stream stream = new Stream("reservoir", fluid);
stream.setFlowRate(50000.0, "kg/hr");
stream.setTemperature(80.0, "C");
stream.setPressure(200.0, "bara");

// 2. Create well with engineering properties
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);

// Geometry
well.setMeasuredDepth(3800.0);
well.setTrueVerticalDepth(3200.0);
well.setWaterDepth(350.0);

// Design conditions
well.setMaxWellheadPressure(345.0);
well.setReservoirPressure(400.0);
well.setReservoirTemperature(100.0);

// 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);

// Tubing
well.setTubingOD(5.5);
well.setTubingWeight(23.0);
well.setTubingGrade("L80");

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

// Well barriers (NORSOK D-010)
well.setHasDHSV(true);
well.setPrimaryBarrierElements(3);
well.setSecondaryBarrierElements(3);

// 3. Run mechanical design
well.initMechanicalDesign();
WellMechanicalDesign design = (WellMechanicalDesign) well.getMechanicalDesign();
design.calcDesign();

// 4. Run cost estimation
design.calculateCostEstimate();

// 5. Get results
System.out.println("Wall thickness: " + design.getProductionCasingWallThickness() + " mm");
System.out.println("Burst DF: " + design.getProductionCasingBurstDF());
System.out.println("Barriers: " + (design.isBarrierVerificationPassed() ? "PASS" : "FAIL"));
System.out.println("Total cost: $" + design.getTotalCostUSD() / 1e6 + "M");
System.out.println(design.toJson());

Well Types and Enumerations

Well Type

SubseaWell.WellType.OIL_PRODUCER     // Oil production well
SubseaWell.WellType.GAS_PRODUCER     // Gas production well
SubseaWell.WellType.WATER_INJECTOR   // Water injection well
SubseaWell.WellType.GAS_INJECTOR     // Gas injection well
SubseaWell.WellType.OBSERVATION      // Observation / monitoring well

Completion Type

SubseaWell.CompletionType.CASED_PERFORATED  // Standard cased & perforated
SubseaWell.CompletionType.OPEN_HOLE         // Open hole (cost factor 0.70)
SubseaWell.CompletionType.GRAVEL_PACK       // Gravel pack (cost factor 1.30)
SubseaWell.CompletionType.ICD               // Inflow control device (1.25)
SubseaWell.CompletionType.AICD              // Autonomous ICD (1.45)
SubseaWell.CompletionType.MULTI_ZONE        // Multi-zone (1.80)

Rig Type

SubseaWell.RigType.SEMI_SUBMERSIBLE  // Semi-submersible (factor 1.0)
SubseaWell.RigType.DRILLSHIP         // Drillship (factor 1.20)
SubseaWell.RigType.JACK_UP           // Jack-up (factor 0.70)
SubseaWell.RigType.PLATFORM_RIG      // Platform rig (factor 0.60)

Casing Design

The WellDesignCalculator performs casing design for each string:

Load Cases

Burst (internal pressure exceeds external):

Collapse (external pressure exceeds internal):

Tension (axial load from casing weight):

Supported Casing Grades (API 5CT)

Grade SMYS (MPa) SMTS (MPa) Typical Use
H40 276 414 Conductor
J55 / K55 379 517-655 Surface casing
N80 / L80 552 655-689 Intermediate (L80 for sour service)
C90 / C95 621-655 689-724 Sour service
P110 758 862 Production casing
Q125 862 931 Ultra-high-strength
13Cr-L80 552 655 CO2 service (CRA)
25Cr 758 862 Severe corrosion (super duplex)

Example: Direct Calculator Usage

WellDesignCalculator calc = new WellDesignCalculator();
calc.setMeasuredDepth(3800.0);
calc.setWaterDepth(350.0);
calc.setMaxWellheadPressure(345.0);
calc.setReservoirPressure(400.0);

calc.setConductorCasing(30.0, 100.0);
calc.setSurfaceCasing(20.0, 800.0);
calc.setIntermediateCasing(13.375, 2500.0);
calc.setProductionCasing(9.625, 3800.0);
calc.setTubing(5.5, 23.0, "L80");

calc.calculateCasingDesign();
calc.calculateTubingDesign();
calc.calculateWeights();
calc.calculateCementVolumes();

Map<String, Object> results = calc.toMap();

Well Barrier Verification

Per NORSOK D-010, subsea wells must maintain two independent well barriers. WellMechanicalDesign.calcDesign() automatically verifies:

  1. Primary barrier requires minimum 2 elements
  2. Secondary barrier requires minimum 2 elements
  3. DHSV (SSSV) required for subsea production wells
  4. Annular pressure monitoring noted as required
design.calcDesign();

if (design.isBarrierVerificationPassed()) {
    System.out.println("Two-barrier principle satisfied");
} else {
    for (String note : design.getBarrierNotes()) {
        System.out.println(note);
    }
}

Cost Estimation

WellCostEstimator

The cost estimator provides detailed well cost breakdowns with regional factors.

WellCostEstimator estimator = new WellCostEstimator(SubseaCostEstimator.Region.NORWAY);
estimator.calculateWellCost(
    "OIL_PRODUCER",       // well type
    "SEMI_SUBMERSIBLE",   // rig type
    "CASED_PERFORATED",   // completion type
    3800.0,               // measured depth (m)
    350.0,                // water depth (m)
    45.0,                 // drilling days
    25.0,                 // completion days
    0.0,                  // rig day rate override (0 = use default)
    true,                 // has DHSV
    4                     // number of casing strings
);

System.out.println("Total: $" + estimator.getTotalCost() / 1e6 + "M");
System.out.println(estimator.toJson());

Cost Breakdown Structure

Category Components
Drilling Rig time, casing material, cement, mud, bits & tools
Completion Tubing, packers, screens, safety valves, rig time
Wellhead Subsea wellhead and Xmas tree assembly
Evaluation Logging, surveys, well testing
Contingency Default 15% on subtotal

Regional Cost Factors

Regional factors affect all cost components (rig rates, materials, services):

Region Factor Typical Well Cost (Oil Producer)
Norway (NCS) 1.35 Highest
UK North Sea 1.20 High
West Africa 1.10 Above average
US Gulf of Mexico 1.00 Baseline
Brazil 0.90 Below average

Bill of Materials

List<Map<String, Object>> bom = design.generateBillOfMaterials();
for (Map<String, Object> item : bom) {
    System.out.printf("%s: %.0f %s%n",
        item.get("name"), item.get("quantity"), item.get("unit"));
}

BOM includes: conductor, surface, intermediate, and production casing (by depth), production tubing, wellhead assembly, DHSV, and cement.

JSON Export

toJson() produces a comprehensive report:

{
  "equipmentType": "SubseaWell",
  "designStandardCode": "NORSOK-D-010",
  "configuration": {
    "wellType": "OIL_PRODUCER",
    "completionType": "CASED_PERFORATED",
    "rigType": "SEMI_SUBMERSIBLE",
    "hasDHSV": true,
    "numberOfCasingStrings": 4
  },
  "geometry": {
    "measuredDepthM": 3800.0,
    "trueVerticalDepthM": 3200.0,
    "waterDepthM": 350.0
  },
  "casingProgram": {
    "conductorOD_in": 30.0,
    "surfaceCasingOD_in": 20.0,
    "intermediateCasingOD_in": 13.375,
    "productionCasingOD_in": 9.625
  },
  "designResults": {
    "productionCasingWallThicknessMm": 8.9,
    "productionCasingBurstDF": 1.52,
    "productionCasingCollapseDF": 2.31,
    "productionCasingTensionDF": 4.87
  },
  "weights": {
    "totalCasingWeightTonnes": 185.3,
    "totalTubingWeightTonnes": 42.5,
    "totalCementVolumeM3": 78.2
  },
  "barrierVerification": {
    "verificationPassed": true,
    "notes": ["PASS: Two-barrier principle satisfied per NORSOK D-010"]
  },
  "costEstimation": {
    "totalCostUSD": 45200000,
    "drillingCostUSD": 24300000,
    "completionCostUSD": 12100000,
    "wellheadCostUSD": 3375000
  },
  "schedule": {
    "drillingDays": 45,
    "completionDays": 25,
    "totalDays": 70
  }
}

Integration with Field Development

FieldDevelopmentCostEstimator uses WellCostEstimator internally when well parameters are configured:

FieldDevelopmentCostEstimator costEst = new FieldDevelopmentCostEstimator(facility);
costEst.setSubseaParameters(15.0, 350.0);     // 15 km tieback, 350m water depth
costEst.setWellParameters(6, 3, 3800.0);      // 6 producers, 3 injectors, avg 3800m MD

FieldDevelopmentCostReport report = costEst.estimateDevelopmentCosts();

Class Reference

Class Package Purpose
SubseaWell neqsim.process.equipment.subsea Equipment class with well engineering properties
WellMechanicalDesign neqsim.process.mechanicaldesign.subsea Design orchestration, barrier verification
WellDesignCalculator neqsim.process.mechanicaldesign.subsea Casing/tubing burst, collapse, tension calculations
WellCostEstimator neqsim.process.mechanicaldesign.subsea Drilling & completion cost estimation

Data Files

File Path Content
WellCostData.csv src/main/resources/designdata/ Well cost parameters by type and rig
CasingProperties.csv src/main/resources/designdata/ API 5CT casing grade properties (SMYS, SMTS)