UK-based Oil & Gas Operator
Dynamic Process Simulation using Black Oil Modelling
UK
Process Engineering
Oil & Gas
Honeywell UniSim
Design
- Overview
As part of a larger project, an established oil and gas operator managing a mature offshore asset from their onshore UK facilities approached Engsolve with a complex challenge. Over time, the characteristics of the produced reservoir fluids had changed due to natural depletion, water breakthrough, and varying gas-to-oil ratios (GOR). As a result, the processing system – originally designed for a different fluid composition – was facing issues with separation efficiency, export quality, and pressure management.
- Description of Services
To accurately predict system behaviour and evaluate processing options, a high-fidelity process simulation was needed. The composition of the oil stream could no longer be reliably represented using traditional component-based models due to its variable nature and the complex interactions between hydrocarbons and non-hydrocarbon components. Engsolve proposed to address these challenges using Honeywell UniSim Design with the Black Oil model.
Challenges
Variable Oil Composition: The fluid was a true multicomponent mixture with properties that changed over time depending on reservoir zones being produced and operational conditions.
Data Uncertainty: Laboratory analyses and PVT data were limited for newer blends, requiring estimation and interpolation of some fluid properties.
Black Oil Modelling Complexity: Although less detailed than full compositional models, the Black Oil approach needed careful calibration to reflect real operational data across different field conditions.
Approach
Engsolve developed a comprehensive process model in Honeywell UniSim using the Black Oil thermodynamic package. This approach allowed the team to simulate the behaviour of oil, gas, and water phases based on key parameters such as solution gas-oil ratio, oil formation volume factor, and viscosity correlations – rather than detailed component-by-component input.
This fluid subsequently formed the input in to a larger process simulation mimicking the plant equipment items and characteristics.
Key steps included:
Model Calibration: Historical operating data and known fluid properties were used to tune the Black Oil parameters to reflect actual field conditions. This included pressure/temperature profiles, separator performance, and fluid yields.
Design and Control Evaluation: Recommendations were developed for control tuning, potential equipment modifications, and adjustments to production rates.
Outcome and Impact
The simulation provided critical insights into the behaviour of the production system under evolving reservoir conditions:
Improved Understanding of Fluid Behaviour: The Black Oil model accurately predicted trends in pump power, heating, gas liberation, and separator loading.
Operational Optimisation: Based on the findings, the client made informed decisions on separator pressure setpoints and heater settings, improving system stability.
Design Validation: The model helped assess whether the existing facilities could handle expected changes over the next production phase, avoiding unnecessary capital expenditure.
Enhanced Forecasting: The operator was able to use the calibrated model as a forecasting tool to evaluate future scenarios and manage production more proactively.
Conclusion
This case highlights the importance of flexible and accurate process simulation in managing mature oil fields with variable fluid compositions. By utilising Honeywell UniSim, Engsolve helped the client address critical operational challenges and make data-driven decisions in a technically complex environment.
