How is natural gas stored?
Demand for natural gas is as high as ever, after all, not only is it suited to a multitude of applications, but it has good availability, is cost-efficient, and is also the most environmentally friendly fossil fuel. Gas storage is used to avoid bottlenecks and balance out seasonal fluctuations. This is because natural gas is produced in identical quantities and imported via pipelines at the same rate throughout the year, but the amounts needed vary – more gas is needed in winter, less in summer.
The complexity involved in gas storage is something Stephan Kreiger, Process Engineer at OMV Gas Storage, knows all about: “The gas travels to the storage facilities via multiple pipelines. Depending on whether the pipelines come from nearby gas fields in Marchfeld or are high-pressure pipelines from the Baumgarten import station, there is a certain level of pressure in the pipelines that often differs from the pressure in the reservoir itself”. OMV’s underground gas- storage reservoirs are found at depths of up to 1,200 meters. And the conditions in the reservoirs themselves also vary – the deeper the gas should be stored, the higher the pressure. “Being able to inject the gas from the pipeline into the reservoir requires the pressure to be equalized and this is achieved with the aid of compressors. It works exactly the same way in reverse when the gas is taken back out of the reservoir”.
Added to this is the fact that the Austrian gas market has grown ever more dynamic in recent years: It’s no longer just about feeding in during summer and withdrawal in winter. Now traders also engage in inflows and outflows of gas from storage in order to realize short-term price advantages on the gas exchanges when demand – and so also prices – is higher.
Injecting and withdrawing natural gas is a complex and dynamic process. SmartStorage assists us in finding the most efficient operational mode for the storage facility – saving energy and thereby ultimately CO2 as well.
Stephan Kreiger, Process Engineer, OMV Gas Storage GmbH
The fast and efficient approach to injection and withdrawal
“Many variables come together there along with hundreds of possible combinations for operating the gas storage sites. Pipeline pressure, free capacity in the reservoirs, the utilization rate of the compressors, the quantities of gas requiring storage… These are just some of the parameters that change hourly and that are needed to determine the optimal operation of the units”, explains Stephan Kreiger. Until now this has been done manually, based on the decades of valuable experience of the employees concerned – the so-called dispatchers.
This is where SmartStorage comes in. The software helps the facilities to run as efficiently as possible by utilizing the differences in pressure in the pipelines as well as the varying depths of the reservoirs. The gas flows are optimized in such a way that the gas more or less flows by itself wherever possible, subsequently reducing the need for compressors. This saves energy and so CO2 as well. In the first year of using SmartStorage, up to 4,000 metric tons a year – that’s a CO2 reduction of around 10 percent.
From thesis to optimization tool
And how does one end up programming a piece of software like this? “It was actually my master’s thesis”, says Stephan Kreiger. “I was studying process engineering at the Vienna University of Technology and came across a job ad for OMV relating to the development of a simulation model for gas storage”. Simulation models are hardly unknown territory for a process engineer, but the special features of the gas storage business were something that took time to absorb: At the beginning there was an intensive research process in order to precisely define all of the underlying steps involved in gas storage and recognize all of its characteristics. This meant that I compiled as much information as possible on how the units function in order to gain an insight into the individual processes. I talked to the operators, analyzed logs and records, delved into the technical documentation… At the end of the day, you need to be able to depict every single point of the facility in the model. You need to know which capacities the reservoirs have available, which quantities of produced gas can be delivered via the pipelines or how much energy is needed to compress, dry and preheat the natural gas”.
After this, mathematical formulae can be created to describe these processes, calculate them and build them into the model. “Over time there is so much data available that you end up with a twin of the real facility, achieved using the simulation model. A twin with which you can simulate exactly how the facility will behave under certain conditions”.
Lots of work and creative solutions
“I think we were all a bit surprised that SmartStorage could be applied so successfully in such a short time. After all, at the start you never know for sure whether a simulation model will function like the real facility. Precisely with a dynamic process like injecting and withdrawing natural gas, there’s so many different components at play and that’s why there’s no single optimal operation mode”, says Stephan.
At the moment SmartStorage still just delivers a snapshot, i.e. it shows all the data only in real time. That said, we are already working on expanding the software to include a forecast function so that in future we can calculate the optimal operation mode for the storage facility ahead of time. But also system failures, i.e. if a compressor breaks down, we should be better placed to offset this thanks to SmartStorage”. And the hard work is already paying off: SmartStorage brings enormous benefits to the plant’s operations. And – as a complete aside – the thesis also got finished.
OMV & The Climate video
Find here our video on the "SmartStorage" software.