| dc.description.abstract | The extraction of gas from the Groningen gas field has led to subsidence and induced seismicity in the area, resulting in both damage to buildings and concern among the inhabitants of Groningen. Detailed information about the lithology and geological structure of the subsurface in this area is therefore needed. In this study, check shot data from borehole SDM-01 is used for testing a new method to determine the depths of lithological interfaces above the reservoir rock. This method is based on the deconvolution between the radial and vertical components of the geophones on a string, called RZ-decon. This method is applied to both real data and synthetic data. The real data is retrieved from check shots around borehole SDM-01, measured by 10 geophones on a string inside the borehole at depths between 2700 and 300 m, inside the Rotliegend reservoir sandstones. The synthetic data is produced using Specfem2D with an input velocity and density model provided by NAM. When comparing the real data with the synthetics, it can be concluded that the RZ-decon method is a useful tool for determining interfaces with velocity contrasts and that the model used in Specfem2D to approximate the reality is quite accurate. When the velocity structure is unknown, this method can be used to estimate the depths of velocity contrasts due to lithological interfaces beneath a set of geophones, using a source from below, such as earthquakes, but the uncertainty in this estimation increases with depth. | |
