GEO-SEQ Subtask 2.3.4: Microseismic Monitoring and Analysis

Abstract

Executive Summary LBNL’s recent analysis of the microseismic data being acquired at well KB‐601 has produced a new result of significantly more microseismic activity than previously estimated. During 2009‐2010, there was background activity of 1 or 2 events per day with a notable increase during the spring‐summer months of up to 20 or more events in a signal day (Figure 1). This level of activity warrants increased effort to obtain quantitative information, and supports plans for expansion of the microseismic monitoring. Quantitative interpretation of these events, including locations, is still hampered by physically unrealistic data from some sensors and uncertainty in which sensors are being recorded and their depth. We now believe that some quantitative analysis will be possible, building upon LBNL’s earlier work and analysis conducted by Pinnacle, and utilizing the sledge‐hammer tests conducted in the fall of 2010 by the JIP. Current acquisition problems include electrical noise, lack of GPS clock timing, and the sensor uncertainty. To address the acquisition problems, we continue to recommend an active‐source recording test with full 144 channel capability (or at least 48 channel). We also recommend a site visit for debugging and repair by a t echnician knowledgeable in the REF TEK recording system and microseismic a cquisition. Detection of Events We have developed an event detection processing flow which has been successful in identifying more events than previous reports. We also have now applied this processing to the entire 2009‐2010 data set. An important assumption in this processing and analysis is that the non‐physical data seen on 3 of the 6 recorded geophones is due to equipment problems or incorrect wiring of the geophones. Since the uphole wiring has been checked, it seems likely that there are downhole wiring problems. We are now using only two geophones (from one of the three REF TEK data recorders) to identify seismic events. Additionally, we are using a spike removal algorithm along with a time‐shifting algorithm (as first applied by Pinnacle) and an automatic event detection algorithm. Spike removal is necessary because of numerous noise spikes presumably electrical in nature. Time shifting (utilizing the electrical noise spikes) is necessary because the recording systems are not receiving GPS clock signals and are therefore drifting in time. Applying these processing tools GEO‐SEQ Subtas k 2.3.4: Microseismic Monitori ng and Analysis Status Report – March 1, 2011 To m Daley, John Peterson and Valeri Kornee v Lawrence Berkeley National Laboratory