Improved definition of faults in the Groningen field using seismic attributes

Marloes Kortekaas,Bastiaan Jaarsma

doi:10.1017/njg.2017.24

Abstract

AbstractThe Groningen field is the largest onshore gas field in Europe. The gas-bearing section comprises aeolian and fluvial Rotliegend sandstones of Permian age and fluvial sandstones of Carboniferous age. Continuous production since 1963 has led to induced seismicity starting in the early 1990s.Faults at reservoir level play a major role in the seismicity in the Groningen field. Fault slip is expected when shear traction is sufficient to overcome frictional resistance on the fault surface. Clear insights into which faults and fault segments are most susceptible to seismicity could be used to optimise production and minimise the seismic risk. To gain these insights, a detailed and realistic fault model is required as input to both statistical analyses on seismicity and deterministic geomechanical modelling of seismogenic behaviour along fault planes. Geometrical seismic attributes and, subsequently, fault planes were extracted from a reprocessed and depth-imaged 3D seismic volume. This resulted in a detailed visualisation of the faults at reservoir level, with extension into the deeper strata below the reservoir in many cases. They represent fault planes with realistic dimensions and shapes. The fault map based on seismic attributes suggests the presence of faults that have not been included in studies on Groningen seismicity before. The improved fault definition correlates with recent earthquake hypocentres. We conclude that a detailed fault model of the Groningen field can be created using 3D seismic attributes and that detailed 3D fault planes can be extracted from these attributes. The results can be used as input to statistical and geomechanical analyses on seismicity.

Highlights

This paper demonstrates that the definition of faults in the Groningen field can be improved using 3D seismic attributes and that detailed 3D fault planes can be extracted from the seismic data
Most of the main faults from the reservoir fault model in red match the faults identified by the ant tracking
This area is the region with the highest seismic event density in the Groningen field

Summary

Introduction

Groningen fieldThe Groningen field is the largest onshore gas accumulation in Europe (∼2900 × 109 Nm3 gas initially in place) (Grötsch et al, 2011; Figs 1 and 2). The first earthquake in the field was recorded in 1991 (ML 2.4) after 1272 × 109 Nm3 of gas had been produced (Hettema et al, 2017). The largest earthquake (ML 3.6) was recorded in 2012 near Huizinge and caused the most damage to date (e.g. Van Thienen-Visser & Breunese, 2015), possibly as a result of its uncommon seismological characteristics, as described in Dost & Kraaijpoel (2013). Production measures aimed at lowering the level of seismicity have been implemented since 2014. These measures were imposed in a few steps after 2014, comprising reduction of the maximum allowed annual production and avoidance of production fluctuations in time and space

Results

Discussion

Conclusion