Empowering pipeline operators to answer a range of interesting questions
The best way to understand a pipeline is to run some experiments. Previously engineers carried this out using specialist apparatus, scale models and observation but now we have pipeline simulators. Although some large-scale experimental rigs still exist today, simulation presents an easier way to investigate countless operating scenarios, expansion studies and much more.
Off-the-shelf pipeline simulation software empowers operators to answer a range of important and interesting questions at the click of a button. Engineering teams can critically examine results of the simulation against their own calculated values.
In this article, we’ll look at how model building within a pipeline simulator is becoming a vital tool for reducing uncertainty and improving efficiency, spanning:
- Core uses for pipeline simulation
- The difference between online and offline simulators
- How pipeline simulation aligns with great model building
Core uses for pipeline simulation
A simulator is used during both the design and operational phases of a pipeline’s lifespan, helping engineers answer important questions and make informed decisions based on the answers.
During the design phase various possible approaches can be explored to meet the intent of the pipeline design. These hydraulic studies cover all aspects of a wide range of scenarios including1:
- Flowsheeting - laying out the network and finding operating conditions
- Specification - selecting appropriate pipe material or equipment from vendors
- Control philosophy - defining a narrative for how best to operate
Once the pipeline is in an operational state, a pipeline simulator can be used to assist teams in the control room. The simulator can assist with both routine and ad-hoc tasks such as1:
- Troubleshooting - identifying issues and overcoming them
- Forecasting - anticipating disruption and avoiding the consequences
- Operations planning - planning for modifications to fluids and flow-rates
- Expansion studies - assessing the retrofits required and cost effective options
- Operator training - demonstrating their competency to regulators
- Optimization - finding the best strategy or debottlenecking capacity
This can be extremely useful for planning unencountered future scenarios too, such as how a pipeline previously used for natural gas will behave if a proportion of hydrogen is blended in. There are many routine tasks for which pipeline simulation has become indispensable in real-time applications. Some of these are outlined in the video below.
Ultimately, a pipeline simulator can support problem solving at all stages of the pipeline lifecycle. From the front-end design of a new pipeline, right through to supporting operations day-to-day and stepping up to answer new questions such as how to adapt to the challenges of the energy transition.
The difference between online and offline simulators
Pipeline simulation software like Atmos Simulation (SIM) Suite use the same underlying model in order to simulate a number of different kinds of scenarios. There are three core categories of applications, namely:
- An offline application (based on constraints)
- An online application (based on metered values)
- A look-ahead application (based on the online model and future supply/demand)
Offline scenarios are used by engineers to perform investigative work. These simulations answer questions like:
- How will existing infrastructure cope with increased flows to meet energy demand?
- How would unplanned events such as outages or supply failures be managed without disruption?
- How can we track and maintain product quality to ensure customer deliveries are on-spec?
Offline simulation is also an excellent tool for training new and existing control room staff. Since hydraulic simulators mimic the pipeline control system, it presents a virtual view of the pipeline during normal and abnormal operating conditions, helping pipeline operators understand the information displayed on the supervisory control and data acquisition (SCADA) system.
Atmos Trainer, the sophisticated operator scoring and qualification module in Atmos SIM, is capable of emulating a variety of scenarios. For instance, a customer in the UK has implemented it across their multiple-inlet multiple-outlet network of pipelines. This was a complex project as the customer required that the pipeline simulator closely resembled how SCADA would really appear in the field, so that their operators could train safely in a realistic offline environment. Emulating pipeline operations for their network involved simulating not just the hydraulics but also a representation of programmable logic controllers (PLCs) at more than 20 stations. Specialist expertise ensured the system responded correctly to operator commands via SCADA screens and handled a variety of operating scenarios.
An online application updates all the calculations based on live meter data. A Real-Time Transient Model (RTTM) combines statistics and high-fidelity physics to find a consistent set of pressures, temperatures and flow rates. It can be used as virtual instruments for locations where there is no meter. It calculates linepack or inventory for each pipeline section. The RTTM can provide gas quality tracking and pipeline inspection gauge (PIG) tracking with estimated time of arrival and It can perform leak detection too.
Forecasting future behavior is a key benefit which simulation software can bring by taking advantage of saved online states to commence user-specified scenarios known as look-aheads. Look-aheads let pipeline operators determine the plausibility of their scheduled plan, or understand what will happen if the pipeline continues to operate in its current state, or assess the consequences of what-if events. This functionality has allowed one customer to predict the pressure trends based on gas demand and production up to 48 hours into the future which has helped optimize operating schedules. Predictive modeling can also be used to see if future scenarios are likely to violate the safe operating conditions.
How pipeline simulation aligns with great model building
The topology of a pipeline network is rarely straightforward. Atmos SIM empowers the users to build intuitively on a visual canvas by drag-and-drop, enabling a good representation to be captured. This high-level abstraction enables a user to build a physical model which has just the right level of detail to simulate their pipeline – more than a schematic, but less than a fully detailed engineering drawing.
Figure 1: A high-level abstraction as a schematic block on a process flow diagram (PFD) alongside a suitable simplified pipeline diagram (SPD) configured in Atmos SIM and a detailed piping and instrumentation diagram (P&ID), all represent the same station
Simulations are as good as the models that underlie them, and although no model is ever a complete version of reality, a well-constructed model allows a pipeline simulator to attain incredibly accurate results, even with a remarkable degree of simplification and abstraction1. This means that we are confident that a simpler model, which retains important parameters and carefully ignores what doesn’t matter, reliably and rapidly produces accurate results. In addition, versatile simulation software like Atmos SIM provides incredible flexibility to run a range of scenarios using the same shared physical model of the pipeline, empowering the user with a great deal of freedom to experiment and explore.
References
1 ”The Atmos book of pipeline simulation”
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Chapter two covers the core components of effective pipeline simulation. Features like an adaptive spatial mesh are known for making pipeline simulators faster, more accurate and reliable for operators.