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Client: Talisman
Location: UK Continental Shelf

Increasing production by an average of 20 MBD.

Slugging and productivity challenges overcome by integrated flow assurance and dynamic simulation teamwork.

Challenge
Xodus was asked to investigate the causes of the production impact of slugging in the pipeline and identify potential solutions to improve output from the Tweedsmuir oil field. The team was composed of operations personnel from operator Talisman, project personnel who understood the background of Tweedsmuir, and Xodus specialists in flow assurance and dynamic simulation who investigated the mechanisms behind the slugging and interrogated the test-run data.

Based on a series of tests completed offshore, Xodus developed a hybrid hydraulic model using links between OLGA and HYSYS dynamics to match the pressure and flow fluctuations. Previous attempts at rationalisation using transient analysis tools had been unsuccessful, indicating that there was a previously unmodelled but potentially significant interaction between the topside control system and pipeline stability. Once the hybrid model achieved a good match with the current operation, Xodus deployed flow assurance experts to assess the slugging through a range of operating conditions and flow rates.

The results showed that the stability of the pipeline system was key to maintaining higher productivity; furthermore, that in this case pipeline stability was an almost linear function of operating pressure. After drawing this conclusion, the operations team tested certain modifications to the system’s operating range that not only resulted in more stable flow, but – as predicted – also attained significantly higher production rates.

Xodus attributes the success of this study to the integrated team, and in particular to the excellent interaction between the personnel from Talisman and Xodus. Another key success factor was Talisman’s willingness to conduct the offshore tests required to gather sufficient information to diagnose the problem and identify potential solutions using model-based extrapolation. Xodus went on to assist Talisman with updates to operating procedures, supported by the results of intensive modelling which aimed to ensure that Tweedsmuir operations under the new conditions were both safe and robust.

Assignment scope

  • Assist in determining offshore trial sequences, objectives and key results
  • Using detailed data regression, determine the underlying system behaviour and produce a calibrated transient model
  • Benchmark the transient model against a number of tests to ensure consistency
  • Investigate alternative subsea and topsides operating options
  • Support for potential modification options to promote stable operation
  • Assist in revision of operating procedures following successful stability trials.

Results
Production from Tweedsmuir increased from circa 13 – 18 MBD to 30 – 40 MBD.