Groningen Gas Field: Heterogeneities characterization of the sediments,by log evaluation.

This research focuses on the analyze of the heterogeneity of the Groningen gas field, i.e. characterization of the reservoir rock and the sealing Zechstein salt on top of the reservoir, by modeling the rock properties of the formations. The aim of this study is twofold, namely to characterize the thickness, shale content and porosity of the reservoir rock and the sealing Zechstein salt. But also to set an geological framework of the Groningen gas field, which can serve as a basic input for subsidence studies and geomechanical modeling of the Groningen field. The Groningen gas field was first discovered in 1959 by well Slochteren 1 and has an horizontal extent of around 900 km2. The reservoir is situated at a depth of 2600-3200 m and the estimated recoverable volume is about 2700 billion m3. It lies within the Southern Permian Basin gas province, an extensive E-W stretched sedimentary basin. In order to analyze the heterogeneity of the sediments (this include the Ten Boer, Ameland and Slochteren member) and the salt rock, software named Quantumgis is used to obtain two dimensional interpolated plots of the three evaluated rock properties. The three rock properties evaluated are thicknesses, shale content and porosities. Well log data have been used to determine these properties. For the thicknesses, the penetration depth of the well bores are used. For the determination of the shale content, gamma-ray and spontaneous potential logs have been used. And eventually, the porosities are derived from density and neutron logs. The used data is obtained from NLOG, the Dutch gas and oil portal. The Zechstein member is a relative thick formation, and show a relative heterogeneous thickness pattern. The Ten Boer member has a relative homogeneous thickness pattern. It has a high shale content and low porosity. Both properties show a heterogeneous pattern. The Ameland member is relative thin and is only present in the northern half of the field, with a high shale content. The distribution of the shale content show a heterogeneous pattern. Finally, the Slochteren member, which is the main reservoir rock, has a heterogeneous thickness pattern. The porosities are high and the shale content is relative low. Both properties show a relative homogeneous pattern. In short, the evaluated formations show a relative heterogeneous pattern for the three rock properties. If one relates the obtained models in this research with the compaction models done by the NAM (NAM,2013), it is clear that production must be reduced or completely stopped in regions with high porosities, since at these regions subsidence values are the highest. This will lead to less compaction and a lower chance of seismic activities.Applied Geophysics and PetrophysicsGeoscience & EngineeringCivil Engineering and Geoscience