Structural modelling and history matching to understand aquifer behaviour in the Hewett Field, UK Southern North Sea.

The Hewett Gas Field is located in the Southern North Sea and is being considered for carbon storage. This study uses production and pressure data to validate a structural model of the field. A thorough understanding of aquifer behaviour observed throughout production is necessary to correctly manage the Hewett Field's potential future use as a carbon storage site. Material balance methods and Cole plots are used to estimate aquifer strength. A conceptual model of aquifer behaviour is developed to explain the observed pressure communication between the Hewett Field and the nearby Little Dotty Field via the shared Bunter aquifer. Within this conceptual model, estimates of changes in hydraulic head between the two reservoirs are made over their productive lifetimes to establish the direction of aquifer movement. Finally, estimates of hydraulic diffusivity are made to establish a characteristic diffusion time for a pressure pulse to be transmitted between the two reservoirs. This was cross-checked with pressure data. A short migration pathway could be observed across the North Hewett Fault that runs between the two reservoirs, which wouldn't have been realised without history matching the pressure and production data to the structural model, although secure storage of CO2 could still be achieved.