Well Testing for reservoir characterisation and production assessment has always been critical, especially in offshore high-pressure, high-temperature (HPHT) environments. A limitation of technology available for HPHT environments in conjunction with strict safety and environmental constraints elevate the operational challenges over those associated with non-HPHT well testing.

The use of a conventional test separator from well opening in gas-condensate well testing is not straight forward, especially in high pressure wells, due to slugging and rapid and continuous phase changes in the early life of the test. Concurrently, accurate flow rate measurement from well opening is crucial for well test interpretation, and estimation of total recovered well effluent. Well test interpretation of fast reservoir pressure response typically observed in HPHT conditions becomes complex, and thus the pressure change needs to be accurately measured at a high scanning rate by downhole memory gauges. Furthermore, and throughout the duration of the well test, personnel safety and environmental responsibility are paramount, thus emphasizing the importance of up-front planning and application of advanced technology, qualified to maximum anticipated conditions, to eliminate and mitigate the associated risks of HPHT well testing.

This paper describes the unique combination of technology, selection, and qualification process of downhole equipment for long duration and anticipated operation conditions that enabled successful well testing on the high profile HPHT Jackdaw gas - condensate field situated in Block 30/2 & 3, the North Sea. The paper also describes the benefits of using a new generation of well test separator, which is equipped with coriolis meters and an adjustable weir plate for optimum separation efficiency in HPHT environments. It also demonstrates how real-time collaboration of experts at multiple sites via a real-time data delivery system was crucial in acquiring high quality data and providing concurrent feedback to ensure safe and trouble-free well testing operations.

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