Application of an Arrival Time and Cross Correlation Value-based Location Algorithm to the Basel 1microseismic Data

摘要

We analysed 2834 microseismic events induced at the Deep Heat Mining Project in Basel, Switzerland. They were recorded by a downhole seismic monitoring system in a six month time period which covers both the stimulation phase from December 02 to December 09, 2006, and the post-injection phase until June 07, 2007. Here, we present a location work-flow to determine high- resolution hypocentres. New P and S wave arrival times for the six downhole geophones were determined by an iterative optimization procedure. 2138 events could be located reliably with an average rms misfit of only 3ms and minimum 8 arrival time measurements. We further refined the locations of multiplet events by applying a recently introduced location algorithm which uses a combination of arrival times and cross correlation values. It is shown that for the largest multiplet consisting of 109 events, the width of the seismically active streak is of the order of 20m. The high- precision locations are a precondition for using the micro seismicity to image the fine- scale structure of the Basel reservoir and for analyzing in detail the spatial-temporal distribution of the Basel 1 micro seismic data, in particular of the multiplet events.