Investigation of abnormal pore pressure variations by the application of seismic inversion in Norne Field, Mid-Norwegian margin Norway

Abstract

The study of pore pressure in a sedimentary basin is the panacea for safe and productive exploitation of the subsurface for hydrocarbon exploration, and field optimization. Pore pressure prediction has an important application in the proper selection of the casing points and reliable mud weight. In addition, using cost-effective techniques of pore pressure prediction, which give an extensive and continuous range of data, is much more affordable than the direct measuring of pore pressure. This research aims at predicting and modeling abnormal pressure variations from the seismic volume through Seismic inversion. The abnormal pore pressure region was identified by applying a normal compaction trend line on P-sonic and density log. This reveals a change in the compaction trend from the interval of 1400 m to 2500 m in well 6608/10_4 and 1350 m to about 2600 m in well 6608/10_4, which is within the Kia formation of about 1360 m towards the end of Not formation about 2600 m before the hydrocarbon reservoir. The estimated pore pressure from the well log suggests the pore pressure from this region to be abnormal, and it complements the normal compaction trend. The predicted pressure from the well was used to calibrate the acoustic impedance in the investigated interval. The result from the seismic inverted volume justifies the predicted pressure from the logs, and the result was able to make clear areas that are not penetrated by well in the volume. The observed seismic inverted result reveals lateral and vertical variations in pore pressure which suggests inhomogeneity in the formation depositional trend.