Effects of Low- and High-Resolution Fault Interpretations on Simulated Pressure Distributions: An Example from the North Sea

Lothe, Ane E.¹, Øyvind Sylta¹, Susanne Sperrevik², Olav Lauvrak² (1) SINTEF Petroleum Research, Trondheim, Norway (2) Norsk Hydro, Bergen, Norway

The lateral pressure distributions in many sedimentary basins are mainly dependent on the sealing properties of the faults that define pressure compartments. Faults are typically interpreted from 2D or 3D seismic datasets. The input fault interpretation will therefore have a fundamental influence on the final pressure distribution results.

The effects of low- and high-resolution fault interpretations on simulated pressure dis­tribution are tested on a dataset from the Tune Field, northern North Sea. First, a low-reso-lution interpretation is used, with only the large faults interpreted. Next, both large and small faults are included. The overpressure generation within the pressure compartments is sim­ulated from mechanical and chemical compaction. The flux between the different compart­ments is calculated during burial of the sediments.

The simulations show high overpressures generated in the deeper western parts of the Viking Graben and hydrostatic pressures in the shallow eastern area. The low-resolution fault map gives a sharp change in the simulated overpressures between the two regions, while using a high-resolution fault map results in a more gradual transition zone. A pressure difference of 14 MPa is measured between wells in the Tune field and a well east of Tune. To be able to match the observed pressure difference, the small N-S striking faults situated in between the wells require higher sealing capacities than expected from juxtaposition analy­sis alone. A reason could be that the reservoir is in contact with deeper burial parts of the sedimentary column east of Tune, than what is used as input in the simulator.