The property and infrastructure being sold include the Bruce, Keith and Rhum fields, three bridge-linked platforms and associated subsea equipment.
The £300 million will be made up of a £12.8 million upfront sum and several other payments depending on future performance, decommissioning costs and fuel prices.
The assets are expected to be sold as a fully operational entity, including around 110 staff.
Bernard Looney, BP Chief Executive of BP Upstream, said: “This is an example of BP’s upstream strategy in action – refreshing our portfolio and focusing our activity on assets which will add most value over the long-term.”
Subject to approval, the companies aim to complete the transfer in late 2018.