Introduction

Compression systems are of fundamental importance to gas storage assets. They are required for one or both of the operating cycles (production and injection). Since they are arguably the most complex of the surface system elements in a storage installation, they have the potential to dictate the flow capability of the facility.

If gas storage operating companies are to maximise the profitability of their asset, they need to ensure that optimisation is applied to the design of new compression facilities and to the operation of existing ones. Mirade can assist them in this aim by providing the following services:

  • Integrated asset modelling (IAM).
  • Feasibility and concept design studies.
  • Forecasting for gas traders.
  • Expansion strategies.
  • Assistance with ongoing management.

Mirade’s centrifugal compression system design, analysis and modelling expertise is particularly well suited to assisting owners and operators of gas storage assets – whether they utilise depleted gas reservoirs or caverns and whether these facilities are located onshore or offshore.

Integrated Asset Modelling

Gas Storage Integrated Asset Modelling

In gas storage assets the operating conditions are particularly dynamic, with pressures at surface facilities being not only a function of current reservoir inventories but of production / injection history too. These can change regularly – even on a daily basis. Integrated asset modelling offered by Mirade can be an invaluable way of converting this myriad of changing conditions into a readily understandable representation of the production / injection capability of the facility. This aids a number of activities, for example:

  • The investigation, definition and validation of options during a concept design study for a new facility.
  • The investigation of options to expand existing facilities, whether this be the addition / upgrade of compression facilities, or the addition of new wells, neighbouring reservoirs or supplementary caverns.
  • The forecasting of production / injection rate capability of an existing installation to facilitate gas trading and operations planning.
  • To facilitate operations planning and management. For example; the investigation of various ‘what if’ scenarios – e.g. NTS (National Transmission System)pressure variation, extreme injection / production cycles, as well as variance in the performances of system elements such as wells or compression trains.
Feasibility & Concept Design Studies

Gas Storage Feasibility & Concept Design Studies

The compression and system design capabilities offered by Mirade which are detailed in the web page titled “compressors in new and young assets” are also applicable to concept design studies for gas storage facilities. In fact, in this application their relevance is particularly pronounced because of the rapid change in pressures and flows across each storage or production cycle.

Matching the Compressor to the System

The matching of the compression system design to varying operating conditions is particularly important for gas storage assets. This is because the facility goes through a full reservoir cycle each season – as opposed to a depletion gas asset where the reduction in reservoir inventory is spread across many years. Consequently, any inadequacies in the compression system design will be apparent very soon after first operation – there will not be the opportunity to have sufficient future visibility as can be the case with pure depletion fields.

In gas storage assets, particularly those utilising depleted gas reservoirs, overall system capability is dominated by the performance of two system elements – the compression system and the wells. The ‘push and pull’ interaction that occurs between the compression and well installations across the production and injection cycles must be fully understood if the system design is to be optimised. Since the particular details of such system characteristics are unique to each gas storage facility; it is inappropriate to simply repeat concept designs and approaches from other assets. A more thorough approach is necessary.

A Thorough Approach

With their ability to develop centrifugal compressor selections and performance curves in-house, together with their integrated asset modelling capability, Mirade can deliver a truly thorough and robust approach to concept design studies for gas storage assets. The fact that it is the same team performing the compressor selection and overall system modelling activities means that the needs and capabilities of the compression system design is fed into the overall asset design and visa-versa. Mirade can therefore offer solutions that represent an optimisation of the overall system and not just one of its elements.

Such an informed approach not only maximises production and injection rates, but also allows asset owners to optimise the application of CAPEX – directing it to the system elements that will yield the greatest return. Mirade can therefore make a substantial contribution to the development of your gas storage asset.

Forecasting for Gas Traders

Forecasting for Gas Traders

Gas trading departments of storage companies have to make informed decisions on a daily basis. For these to be realistic they must have an accurate statement of the current injection / production rate capability of the asset. This can be challenging since the picture is dynamic – reflecting not only preceding injection and production quantities, but the time across which they occurred (in assets utilising depleted gas reservoirs).

Mirade can work with the client to develop integrated system models and supplement these with gas inventory reporting and modelling procedures. These can then be utilised by both production and commercial staff to facilitate operations planning and gas trading activities.

Mirade can therefore provide operations staff and traders with platforms that provide real and up-to-date representations of production / injection capability – invaluable aids to their daily decision making and planning needs.

Expansion Strategies

Gas Storage Expansion Strategies

By building upon integrated models of existing gas storage facilities, Mirade can identify opportunities to increase storage capacity and flow rates via various expansion options. Mirade can provide inputs to the client’s investment decision processes by providing cross-season injection and production profiles for each expansion option in addition to the baseline (existing) capabilities.

The flow-uplift for each option across various reservoir inventories can then be related to corresponding typical gas prices at that point in typical storage seasons. This can be utilised to demonstrate the increase in revenue yielded by each expansion option and compared to its required CAPEX.

Ongoing Management

Ongoing Management of Gas Storage Assets

Keep Rates High

In addition to assisting operators with models and procedures to understand daily production / injection capability, Mirade can assist in the ongoing management of gas storage facilities.

The profitability of the asset is closely tied to its ability to maximise rates during periods of greatest price swing. Therefore, maintaining flow capability as high as possible is a crucial objective in the ongoing management of facilities. Mirade bolster this strategy by providing performance reviews and action plans.

Performance Reviews & Action Plans

Mirade can provide periodic reviews of operating data across the facility to map the current and historical performance of elements in the overall gas storage asset. These reviews can identify instances where performance degradation has occurred or is ongoing in surface and subsurface items.

Mirade can then quantify the effect of such performance deviations on rate capability across the production and injection cycles. Where remedial measures are justified, Mirade can perform further system modelling to determine the extent to which CAPEX and intervention time can be offset against enhanced rates. Having identified the most appropriate solutions, Mirade can develop detailed action plans.

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