Independent Production Forecasting of Current Facilities with or without Re-design

To ensure that the new re-design will operate in the production facility we test the new compressor using the GASMAN model. GASMAN is the integrated model of the production system which includes the gas compression system, the processing facility, the gas turbine drive, the recycle system and the process control set points.
To more accurately optimise the compressor design, the effect of changing reservoir and well performance must also be included in the GASMAN model. This is achieved by the integration of subsurface system with the compression facilities; this provides a more robust solution and ensures that the reservoir and sub-surface performance risks are included in the new compressor design.

The GASMAN model includes a sophisticated material balance method for reservoir performance and for determining well hydraulics. The model includes the gas influx and water influx terms, which allows for water aquifer support. The model has been extensively tested and history matched with many large and small gas fields using reliable data.
This is achieved by downloading historical data from the DCS systems of the existing facility.
 
For reservoir and well performance it is possible to perform the history matching for the past 5 - 10 years or longer if the data is available in a suitable format. Recently the GASMAN model was used to history match a gas field which has been in operation for the past 40 years.




However, for compressor performance only recent data is required for validating the model. After the GASMAN model has been verified against field data with the current compressor design, the alternative compressor designs are installed. The model is run in the dynamic mode for the next 5 - 10 years to verify the compressor performance. After a few iterations it is possible to identify the most appropriate compressor designs which would provide the best performance with the reservoir and well combination. It is possible to design compressors which would last for longer periods but MSE's experience shows that this compromises the compressor design and marginalizes its performance.

The revised compressor design, after testing, is then passed  on to the compressor vendor for final confirmation. The vendor selection is then re-run in the GASMAN to verify the performance. It is normal practice to degrade the performance of a compressor from new to allow for in service performance variations. MSE has developed and maintains a large database of machinery performance; the database provides a good indication of expected performance variations in the field.