Dynamic Process Simulation

Xodus Group’s integrated approach, underpinned by state-of-the-art simulation technology, delivers risk reduction, rapid evaluation and cost savings.

Simulation is a virtual representation of an existing or future plant. Changes in equipment operating conditions and process control can be made to models rapidly and cost-effectively. This allows evaluation of operating scenarios, all offline, with no risk to production. A steady-state simulation will give a snapshot of a process, producing an idealised view of flow rates, pressures and temperatures. Dynamic models take into account time, leading to the evaluation of transient conditions, i.e. slugging, start-up and shutdown, which are typically when plant limitations can be reached.

Knowledge of the data requirements to populate the model, knowledge of the simulation package to build the model and astute interpretation of the model output is crucial to delivering the optimum solution. All Xodus Group personnel engaged on dynamic process simulation projects have design and operations support experience and are used to using the simulation as a tool to reach a ‘real-world’ engineering solution.

Specialist experience
With a combined total of over 100 man-years of simulation experience, Xodus personnel are dynamic process simulation specialists, notably in our industry-leading experience linking HYSYS to external applications.

As well as using Aspen toolkits to link HYSYS to pipeline simulators (such as OLGA, PROSPER and GAP) and Microsoft Excel, Xodus develops custom links to control systems, leveraging the Component Object Model (COM) and Object Linking and Embedding for Process Control (OPC) communication protocols. Xodus has also delivered an industry first by using a dynamic process simulation at the heart of an allocation system, reading in-plant data to the model then calculating and publishing allocation reports to a client’s intranet.

Integrating engineering and technology
Utilising the experience within Xodus provides the engineering knowledge of subsea, flow assurance and topsides that allows us to provide world-class simulation. Our software know-how enables us to deliver this via a state-of-the-art software platform.

Previous projects include:

  • Slug control studies on oil train level control and reciprocating compressor control
  • Produced water design stage control review
  • Compressor control optimisation studies
  • Rigorous hydraulic and thermodynamic blowdown analysis of onshore and offshore facilities
  • Over-pressurisation and Instrument Overpressure Protection System (IOPPS) analysis of process facilities
  • Development of operator training systems
  • Control solution for two platforms exporting oil to a common manifold.

Slug control
Xodus has developed a number of slug control solutions ranging from cascade control through to non-linear error squared control and into custom designed algorithms. Our approach is to look at each system individually and through a combination of experience and modelling, determine the optimum solution for the system.

Our flow assurance expertise allows accurate determination of the slugging type and slugging source, which ultimately determines the optimum solution: a change in fluid phase rates; a change in choke or riser valve position; feed forward control based on early slug detection; primary separator control; or a combination of these.

The ability to link a transient pipeline simulator (i.e. OLGA) to a dynamic topsides simulator (e.g. HYSYS) can be key to carrying out this type of analysis.

Compressor control
Compression optimisation studies by Xodus engineers range from improving control of a single electric motor driver compressor with a DCS based flow vs. differential pressure anti-surge algorithm to rationalising three parallel trains of three stage compression with 19 Compressor Control Corporation (CCC) anti-surge and performance controllers, to designing and commissioning a load sharing speed controller for turbine driven export compressors.

Sub-optimal compressor operation can lead to excessive recycle valve wear, more frequent maintenance intervals, more frequent trips (the costs of which can be exacerbated by loss of gas lift), increased fuel consumption and subsequent emissions. Xodus Group have a HYSYS extension (emulation) of CCC anti-surge and performance controllers that allows rigorous surge and load sharing analysis of centrifugal and reciprocating compressors.

Operator training systems
Linking HYSYS to control systems and SCADA graphics allows Xodus to provide cost-effective and realistic operator training. The operator training systems we design range in complexity from simple process trainers with a few operator screens mocked up in Microsoft Excel to multiple models distributed across several PCs linked to control interfaces. They can be used for personnel who are new to the industry, or as refresher training for more experienced personnel.

Online model deployment
Xodus personnel have industry leading experience in the online deployment of dynamic process simulation models covering pipeline operations management, pipeline integrity monitoring, process monitoring / optimisation and allocation. Our online models satisfy the need to run reliably and continuously, with input data errors captured and output errors reported without crashing the model.

Business benefits
Dynamic process simulation is now an established step in the engineering process to design, upgrade and de-bottleneck plant equipment.

The primary benefits of simulation lie in the risk reduction through offline analysis and cost savings achievable via:

  • Ratification of a design prior to purchase of equipment – rapid evaluation of different feed gas oil ratios if a comprehensive well test programme was not carried out or if confidence is low in respect of reservoir analysis, perhaps due to analysing old fluid samples
  • Confidence in control system performance prior to installation and commissioning – avoiding mistakes in control system design that could lead to sub-optimal operation, an overrun shutdown or additional shutdown to install additional instrumentation
  • Optimisation of separator-level control experiencing slugging conditions – offline evaluation of various control strategies
  • Minimising off specification oil sent to slops tanks due to slugging or start-up conditions
  • Retuning of compressor anti-surge and performance controllers to optimise production following the introduction of additional gas to the process
  • Development of an operator training system to maximise process understanding and subsequent process uptime
  • Development of real-time pipeline models for XPLORE pipeline monitoring systems.