High resolution seismic mapping of a shallow aquifer

Abstract

In the past, geological analysis did not often incorporate seismology into integrated environmental studies. This was due in part to the expense of running multifold reflection surveys, and additionally the lack of expertise of the individuals involved in the environmental and groundwater fields. However, in recent history, the progress of technology and increasing need for more detailed non-invasive investigations of subsurface geology has encouraged the use of imaging methods such as CDP reflection seismology. The Dalmeny project was designed to address many of the issues related to the differences between a standard petroleum seismology survey and a shallow survey in glaciated areas. These differences exist in three principle areas: survey design and data acquisition (CDP reflection profiling), data processing, and interpretation. The post-Cretaceous geology of central Saskatchewan is composed of several till and sand units (e.g. Dalmeny aquifer) and a non-glacial incised valley aquifer (Tyner Valley aquifer). The sands of the Dalmeny and Tyner Valley are major aquifers and were the principle targets for reflection surveying. Utilisation of wave equation modelling in the survey design process provided opportunities to optimise survey parameter values economically. Additionally, the use of non-standard acquisition techniques provided enhanced data quality and increased resolution over previous shallow seismic surveys. Rigorous interpretation techniques have been used to extract as much information as possible from the Dalmeny data set. Advanced interpretation techniques such as complex trace attribute analysis and velocity inversion were attempted. Results indicate interesting variation and complexities which were not apparent on the standard section. Near surface analysis of refraction information was used to quantify elastic properties (velocities) for the highly weathered shallow(< 10m) strata. The results of the Dalmeny project provided have shown that the acquisition of high frequency (> 200 Hz) seismic data is possible in a glaciated terrain. The detailed analytical procedure used in obtaining the acquisition parameters facilitated these results. Enhanced data processing using advanced algorithms available for conventional seismology significantly increased the frequency content and data quality. Note:This thesis contains maps that have been sized to fit the viewing area. Use the zoom in tool to view the maps in detail or to enlarge the text.