Sales Contracts

The sales contract system enables specification verification and compliance checking for natural gas quality.

Overview
Architecture
Creating Contracts
Contract Specifications
Usage Examples
Database Integration

Overview

Location: neqsim.standards.salescontract

Purpose:

Define quality specifications for gas sales points
Verify gas quality against contractual limits
Generate compliance reports
Support multi-specification contracts

Classes:

BaseContract - Main contract implementation
ContractInterface - Contract interface
ContractSpecification - Individual specification

Architecture

Class Hierarchy

ContractInterface
    │
    └── BaseContract
            │
            ├── ArrayList<ContractSpecification>
            │       │
            │       └── StandardInterface (method)
            │
            └── Database connection (gascontractspecifications)

Workflow

1. Create Contract (from database or manually)
        ↓
2. Add Specifications (linked to standards)
        ↓
3. Run Compliance Check
        ↓
4. Generate Results Table
        ↓
5. Display/Export Results

Creating Contracts

From Database

import neqsim.standards.salescontract.BaseContract;
import neqsim.standards.salescontract.ContractInterface;

// Load contract from database by terminal and country
ContractInterface contract = new BaseContract(
    thermoSystem,    // Gas composition
    "Kaarstoe",      // Terminal name
    "Norway"         // Country
);

Programmatic Creation

// Create empty contract
ContractInterface contract = new BaseContract();

// Or with basic water dew point spec
ContractInterface contract = new BaseContract(thermoSystem);

Contract Specifications

ContractSpecification Class

Each specification contains:

Field	Description
`name`	Specification name
`specification`	Description
`country`	Country code
`terminal`	Terminal/delivery point
`standard`	StandardInterface method
`minValue`	Minimum acceptable value
`maxValue`	Maximum acceptable value
`unit`	Unit of measurement
`referenceTemperatureMeasurement`	Reference T for measurement
`referenceTemperatureCombustion`	Reference T for combustion
`referencePressure`	Reference pressure
`comments`	Additional notes

Creating Specifications

import neqsim.standards.salescontract.ContractSpecification;
import neqsim.standards.gasquality.Draft_ISO18453;

// Create water dew point specification
StandardInterface waterDPMethod = new Draft_ISO18453(thermoSystem);

ContractSpecification waterSpec = new ContractSpecification(
    "Water Dew Point",           // Name
    "Maximum water dew point",   // Specification description
    "Norway",                    // Country
    "Kaarstoe",                  // Terminal
    waterDPMethod,               // Calculation method
    -20.0,                       // Minimum value
    -8.0,                        // Maximum value
    "°C",                        // Unit
    15.0,                        // Reference T measurement
    15.0,                        // Reference T combustion
    70.0,                        // Reference pressure (bar)
    "At 70 bar"                  // Comments
);

Available Standard Methods

Method Name	Class	Purpose
`ISO18453`	`Draft_ISO18453`	Water dew point
`ISO6974`	`Standard_ISO6974`	Gas composition
`ISO6976`	`Standard_ISO6976`	Calorific values, Wobbe
`BestPracticeHydrocarbonDewPoint`	`BestPracticeHydrocarbonDewPoint`	HC dew point
`SulfurSpecificationMethod`	`SulfurSpecificationMethod`	H2S and sulfur
`UKspecifications`	`UKspecifications_ICF_SI`	UK ICF/SI specs

Usage Examples

Basic Contract Check

import neqsim.thermo.system.SystemSrkCPAstatoil;
import neqsim.standards.salescontract.BaseContract;

// Create gas composition
SystemInterface gas = new SystemSrkCPAstatoil(273.15 + 15, 70.0);
gas.addComponent("methane", 0.90);
gas.addComponent("ethane", 0.05);
gas.addComponent("propane", 0.02);
gas.addComponent("CO2", 0.02);
gas.addComponent("nitrogen", 0.005);
gas.addComponent("water", 30e-6);  // 30 ppm water
gas.setMixingRule("CPA_Statoil");

// Load contract from database
BaseContract contract = new BaseContract(gas, "Kaarstoe", "Norway");

// Run compliance check
contract.runCheck();

// Get results
String[][] results = contract.getResultTable();
int numSpecs = contract.getSpecificationsNumber();

System.out.printf("Checked %d specifications%n", numSpecs);

// Display results
contract.display();

Custom Contract

import neqsim.standards.salescontract.*;
import neqsim.standards.gasquality.*;

// Create empty contract
BaseContract contract = new BaseContract();

// Add water dew point specification
Draft_ISO18453 waterMethod = new Draft_ISO18453(gas);
waterMethod.setReferencePressure(70.0);
ContractSpecification waterSpec = new ContractSpecification(
    "Water DP", "Water dew point max", "Export", "Platform",
    waterMethod, -100, -8, "°C", 15, 15, 70, ""
);
contract.addSpecification(waterSpec);

// Add Wobbe index specification
Standard_ISO6976 wobbeMethod = new Standard_ISO6976(gas, 15, 25, "volume");
ContractSpecification wobbeSpec = new ContractSpecification(
    "Wobbe Index", "Wobbe index range", "Export", "Platform",
    wobbeMethod, 47300, 51500, "kJ/m³", 15, 25, 1.01325, ""
);
contract.addSpecification(wobbeSpec);

// Add GCV specification
ContractSpecification gcvSpec = new ContractSpecification(
    "GCV", "Gross calorific value", "Export", "Platform",
    wobbeMethod, 37500, 43000, "kJ/m³", 15, 25, 1.01325, ""
);
contract.addSpecification(gcvSpec);

// Run check
contract.runCheck();

Attaching Contract to Standard

import neqsim.standards.gasquality.Draft_ISO18453;

// Create standard with contract
Draft_ISO18453 waterDP = new Draft_ISO18453(gas);
waterDP.setSalesContract(contract);

// Calculate
waterDP.calculate();

// Check specification compliance
if (waterDP.isOnSpec()) {
    System.out.println("PASS: Water dew point within specification");
} else {
    System.out.println("FAIL: Water dew point out of specification");
}

Contract Results Table

// After running check
String[][] results = contract.getResultTable();

// Results table structure:
// [row][0] = Specification name
// [row][1] = Measured value
// [row][2] = Min specification
// [row][3] = Max specification
// [row][4] = Unit
// [row][5] = Pass/Fail status

System.out.println("Specification | Value | Min | Max | Unit | Status");
System.out.println("--------------|-------|-----|-----|------|-------");

for (int i = 0; i < contract.getSpecificationsNumber(); i++) {
    System.out.printf("%13s | %5s | %3s | %3s | %4s | %6s%n",
        results[i][0], results[i][1], results[i][2],
        results[i][3], results[i][4], results[i][5]);
}

Database Integration

Database Table Structure

Table: gascontractspecifications

Column	Description
`NAME`	Specification name
`SPECIFICATION`	Description
`COUNTRY`	Country code
`TERMINAL`	Delivery point
`METHOD`	Calculation method name
`MINVALUE`	Minimum value
`MAXVALUE`	Maximum value
`UNIT`	Unit string
`ReferenceTdegC`	Reference temperature
`ReferencePbar`	Reference pressure
`Comments`	Additional notes

Method Name Mapping

Database Method	Class
`ISO18453`	`Draft_ISO18453`
`ISO6974`	`Standard_ISO6974`
`ISO6976`	`Standard_ISO6976`
`BestPracticeHydrocarbonDewPoint`	`BestPracticeHydrocarbonDewPoint`
`SulfurSpecificationMethod`	`SulfurSpecificationMethod`
`UKspecifications`	`UKspecifications_ICF_SI`

Querying Contracts

// Contracts are loaded by terminal and country
BaseContract norwegianContract = new BaseContract(gas, "Kaarstoe", "Norway");
BaseContract ukContract = new BaseContract(gas, "StFergus", "UK");
BaseContract belgianContract = new BaseContract(gas, "Zeebrugge", "Belgium");

Typical Specifications

Norwegian Pipeline Gas

Parameter	Min	Max	Unit	Reference
Water dew point	-	-8	°C	70 bar
HC dew point	-	-2	°C	cricondentherm
GCV	36.5	44.0	MJ/Sm³	15°C/15°C
Wobbe index	47.0	52.0	MJ/Sm³	15°C/15°C
CO₂	-	2.5	mol%	-
H₂S	-	5	mg/Sm³	-

UK NTS Gas

Parameter	Min	Max	Unit	Reference
GCV	36.9	42.3	MJ/m³	15°C/15°C
Wobbe index	47.2	51.41	MJ/m³	15°C/15°C
ICF	-	0.48	-	-
SI	-	0.60	-	-

Best Practices

Contract Management

Store specifications in database for consistency
Version control specification changes
Document reference conditions clearly
Include measurement uncertainty allowances

Compliance Checking

Run checks before custody transfer
Log all specification results
Alert on near-limit values
Track specification trends over time

Integration

Link to online analyzers for real-time checking
Interface with SCADA systems
Generate automatic compliance reports
Archive historical compliance data

References

EASEE-gas Common Business Practice 2005-001 - Harmonisation of Natural Gas Quality
EN 16726 - Gas infrastructure - Quality of gas - Group H
ISO 13686 - Natural gas — Quality designation
GTS (Dutch) - Gas quality specifications
National Grid (UK) - Gas Ten Year Statement

Sales Contracts

Comprehensive Java library for thermodynamic, physical property, and process simulation. NeqSim provides tools for PVT analysis, phase equilibria, transport properties, and full process simulation.

Sales Contracts

Table of Contents

Overview

Architecture

Class Hierarchy

Workflow

Creating Contracts

From Database

Programmatic Creation

Contract Specifications

ContractSpecification Class

Creating Specifications

Available Standard Methods

Usage Examples

Basic Contract Check

Custom Contract

Attaching Contract to Standard

Contract Results Table

Database Integration

Database Table Structure

Method Name Mapping

Querying Contracts

Typical Specifications

Norwegian Pipeline Gas

UK NTS Gas

Best Practices

Contract Management

Compliance Checking

Integration

References