This paper describes a unique combination of equipment and techniques that enabled an ESP-DST well test on a shallow, horizontal well drilled in a faulted and heterogeneous reservoir with complex fluids, in Arctic conditions.

The technical challenges of the performed well test included designing a bespoke ESP-DST string compatible with the shallow reservoir and designing a surface well test spread capable of efficient separation for safe and environmentally friendly disposal, and obtaining accurate flow rate measurements, as well as performing a test with interpretable data given the uncertainty and complexity of the formation, and the complexity of the well itself.

The success of the performed well test was the result of an integrated approach to well test design and real-time support provided throughout. This process included the selection of optimum ESP-DST string design for multizone testing in a high angle well including an innovative arrangement of an ESP encapsulated in a POD and installed in the riser. Integration of ESP with the surface well test package was also important and the design of the surface well test package included a Coriolis type of separator and multiphase flow meter for accurate flow rate measurements.

During drilling, the contingency plan to mitigate against losses was implemented which had a significant effect on the well testing program. To address this, and to understand if the well objectives could still be achieved, an uncertainty-based well test design and interpretation methodology, taking into account reservoir uncertainties and their interaction with each other, which uses numerical models and a global sensitivity analysis method was applied. This method identifies which uncertain reservoir parameters can be interpreted confidently and indicates the test duration. From the hundreds of numerical simulation cases produced during the design stage of the test, matches were obtained during monitoring to give an indication of the future pressure behavior, which allowed the duration of final build-up to be optimized.

The ESP-DST well test was successfully performed on a horizontal well drilled in the Wisting discovery in the Barents Sea. The well was successfully free flow tested giving a maximum achieved flow rate of 5,000 barrels of oil equivalent per day. All the well test objectives were successfully achieved, despite the change to the contingency drilling plan.

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