Project:

The UK NNS Heather Field has been in production for 38 years with some 90 wells; producers, water injectors and re-completions. The development plan called for producers, supported by (expected) aquifer influx, however, early decline (left) dropped parts of thefield below the bubblepoint, leading to liberation of gas: some producers were quickly converted to water injection, but were – as a consequence – not always in optimum positions.

All producers were gas-lifted, making gas production monitoring difficult. PVT was believed to vary considerably throughout the field. So, production of liberated gas was historically not considered a major issue. Material balance became doubtful. Injection water broke through more quickly than expected, indicating considerable heterogeneity, in common with many other Brent oil fields. The computer capabilities at the time conspired against a sophisticated reservoir model description and this lead to a “ [widespread] belief [before 2014], that modeling of the Heather Field was a venture of such complexity, that the results would always be of limited use, because the remaining unresolved issues …”

For EnQuest, the arrival of tNavigator® meant that Heather could be history matched in a multi-layered model with realistic heterogeneity, where water sweeps very small thiefzones, thus defining the remaining oil-in-place. Without prohibitive runtimes. Rejuvenation of the field is now a real possibility!