The Exceptional 4D Oil Charge History of the Wytch Farm Field (Wessex Basin, UK)

Previous published oil charge models of the Wytch Farm Field point to the importance of the paleo-structural configuration of the greater Wytch farm area, but remain simple and non-quantitative. They do not explain why the charge has been successful only for Wytch Farm and a series smaller satellite traps along a fill/spill chain to the west, but did not work elsewhere.

Structural modeling and restoration, paleo-fault analysis and paleo-drainage area analysis were carried out to recreate a pre-inversion 3D structural configuration of the greater Wytch Farm area. In this restored space, corresponding to Cretaceous times, the oil kitchen and carriers beds of the hanging wall were modeled to be locally in contact with the footwall carrier beds and reservoirs. This past zonal juxtaposition along the fault system occurred at some specific locations only.

Pre-inversion drainage area-based oil migration analysis and petroleum systems modeling were applied to investigate the duration of the localized “charge window”, cross-fault charge amounts and rates. With this new quantitative 4D charge model for the greater Wytch Farm area, oil and gas discoveries, shows and seeps, the absence of charge in other structures, and the successful charge of the Wytch Farm oil field can be explained.