Geode Used for Time-Lapse Reservoir Monitoring

The research team led by Dr. Douglas Schmitt at the University of Alberta in Edmonton acquired a 240 channel Geode system in late 2000. Since then the system has been used in a wide variety of locations for many different purposes. The primary purpose of the system has been to carry out high fidelity time-lapse surveys over a heavy oil production facility which steam is injected by horizontal wellbores to the reservoir. In this application, very closely spaced common midpoints (1.5-m) allow high spatial resolution studies of the changes in the reservoir to be monitored with time. The system has been used one seven different field trips to the same site allowing the first 2D seismic ''movies' to be made. The seismic source for this study is a 6000 lb IVI vibrator, the advantage of the geodes is that they carry out the correlation of the up to 14 second sweep at 1-ms on the boxes speeding up data acquisition considerably.  Figure 1 shows an example of a difference section acquired in the surveys.

Figure 1: Time-lapse-seismic section shows differences in reservoir characteristics as steam flood front liberates oil from pore spaces.

While seismic monitoring has been the main purpose of the system, it has also been very busy in a number of other applications. The system was used for nearly 3 weeks at temperatures of -35 degrees C at the Mallik Scientific Wellbore site in February and March of 2002 for imaging studies of the near surface permafrost layer. At this site the Geodes were also configured to acquire passive microseismic arrivals produced during minifrac pre-production tests into a gas hydrate reservoir.  The system has also been used for short passive tests of the seismic noise induced by large heavy haulers used in the oil sands mines in Northern Alberta, the purpose of this work is to see how ground motion may correlate with structural damage occurring in these large machines.

Figure 2: High resolution reflection/refraction record collected with U of A's 240 channel system

The equipment is used to collect both reflection and high resolution refraction records in the University of Alberta Field School in Southern Alberta, an example of one such refraction record is shown in Figure 2. Finally, the system was sent to Italy to assist colleagues there in near surface ground water studies in Milan and initial noise tests near Padua in advance of possible larger scale seismic studies of hydrothermal resources there.This coming summer, the system will be used for an environmental noise level blasting survey related to fish habitats in the North West Territories

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