D6.3: Stress and pressure simulations, "Fox Field", Halten Terrace area

Joachim Rinna et al.

Pressure and stress distribution is simulated, both on large scale and in a smaller area in the Halten Terrace area. The study area is situated in the eastern part of the Halten Terrace area, covering a producing gas and condensate field named Mikkel. The gas field is situated close to the Bremstein Fault Complex that defines the border to the Trøndelag Platform area.

To avoid confusion, a synthetic dataset named "Fox Field" is used in this study, built on data from the Mikkel Field. Also an extended area around the Fox Field is used, to give the boundary conditions to the Fox field model. The aim has been to evaluate CO₂ migration, and pressure build ups. Several injection rates and sites have been tested. Two synthetic models are built:

• Fox Field, synthetic data set in a small area (12X20 km)
• Extended area, around the Fox field (36X50 km)

Several simulations tools have been used:

• A 'tank model' using storage-DGF (depleted gas fields) and storage-AQUIFER has been used to simulate CO₂ storage
• Reservoir modelling using Eclipse 300
• Pressure modelling using Pressim Production

The tank model reproduces the Flowing Bottom Hole Pressure response of the Eclipse model of the Fox field. The tank model has a systematic lower estimate of the total CO₂ injected in the reservoir compared to the Eclipse model. The reason for this is that the tank model does not model the structure and the influence of the reservoir.

The Pressim simulator represents a simplified scheme to quickly calculate the overpressure within the formation during and after injection period. The simulations indicate that Pressim tends to overestimate the pressure during injection period, but can assess the long term (>100 years after injection stop) overpressure distribution within the carrier unit. The fault description is the central and vital input for this approach.