Gas flow optimization for UGS

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Peter Humaj

July 08 2019, 3 min read

Experience and benefits of gas flow optimization methods in Slovakia.

Underground gas storages (UGS) represent a unique infrastructure combining reservoir with gas surface facilities. The most important part of variable costs of each storage is fuel consumption for compression work (gas or electricity) for gas injection but also for withdrawal depending on storage characteristics. For increase the  efficiency company has to optimize storage dispatching management and install more efficient compressors.

What was the problem?

Company storage complex uses 8 entry/exit points, 11 gathering stations, 13 reservoirs, 14 compressors and numerous intersections of pipelines with various pressure levels. In addition, the storage is interconnected with several gas grids. Considering amount of gas injected and withdrawn in storage operation, even savings amounted to a few percent of fuel consumption can lead to significant economic benefits over year. Company needs to optimize processes of gasflow and try to save as much as possible.

What can we do?

To support dispatching in their decision making processes a dedicated Gas Flow Optimization Software was implemented by this company together with software company IPESOFT.

Generally there are two variants of optimization we apply on our storage.

1.      Long-term optimization and simulations are mostly used for maximization of injection/withdrawal rates and storage capacity by systematic monitoring and controlling of  this process.

2.      Short-term optimization aimed at reducing of fuel consumption includes optimization of gas flows, compressor workload, pressure drops reduction and operational chemicals diminution. Main task of such optimization is the proposal of a gas flow, assets used to process this flow and their parameters, which leads into minimization of KPIs (mainly fuel gas).

The overall process of daily management and dispatching of standard UGS supported by dedicated optimization software.

Main functions of the Optimization Software for this company developed together with IPESOFT:

1.      Gathering the data about customers’ nominations, status of each reservoir and availability of subsurface and surface gas processing assets, geological priorities, conditions of TSO, DSO network, especially pressures and capacities of Entry/exit points.

2.      Calculation and recommendation to dispatcher about optimal gas flow within storage. Implemented optimisation algorithms ensure the fulfilment of client nominations with minimal consumption of energy used for compression and processing while respecting all input constrains, availability and technical/safety limits.

3.      Reporting of selected data about actual efficiency and effectiveness of storage operation and management.

Optimization Software was put into standard operation in company in 2017 after more than 2 years of development and testing. Its interface is shown at figure below.

What does implementation brings to the company and how much have we saved?

Real results shows that implementation brings both financial and non-financial benefits. Most important benefits are:

  • Decreased fuel gas consumption - overall saving is more than 4%
  • Predictable variable costs of storage operation,
  • Focusing maintenance costs into most important assets,
  • Optimization of grid and infrastructure design,
  • Increasing of operational safety,
  • Formalisation of the planning processes,
  • Standardisation of support services between commercial and technical dispatch centres,
  • Increasing amount of business partners,
  • Flexible commercial products,
  • Evaluation of storage operation efficiency,
  • History of agreed plans, parameters and balances,
  • Supporting of continual improvement in overall efficiency.

For evaluation purposes we decided to use a comparison between results proposed by software and dispatcher's manual control of injection in season 2017. Altogether more than 100 days (scenarios) were evaluated up to date. There are two categories of daily nominations:

1.      Standard scenarios– free-flow or less than 4 compressors are needed

2.      Complex scenarios– more than 4 compressors are requested

Based on   this data we can estimate that overall savings achieved by Optimization Software is more than 4%, out of   that complex scenarios delivered more than 3%.

Results   also show that in almost 20% of scenarios the fuel gas saving was 10% or   more, what is quite significant saving potential.

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