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Aquistore: Listening Closely and Leading the World
Monday, May. 6, 2013

 

Regina - Below the surface of south-eastern Saskatchewan, someone or something is listening.

Six-hundred-and-thirty somethings to be exact.

Outside Estevan, Saskatchewan lays one of the most extensive permanent seismic arrays to be used for tracking carbon dioxide (CO2) movement in the subsurface. As part of the Aquistore project, this permanent seismic array is the first in the world to be used for CO2 monitoring. Aquistore is an independent research project which is demonstrating the storage of carbon dioxide 3.4 km deep underground. By storing liquid CO2 in a saline sandstone formation, Aquistore will demonstrate the scientific and economic feasibility of reducing greenhouse gases through dedicated CO2 storage.

As spring oh-so-slowly arrives on the Canadian prairies, Aquistore is warming up for what will certainly be another busy summer. The project’s 2012 operations were focused on the drilling and evaluation of two heavily instrumented wells, the two deepest in Saskatchewan: an injection and observation well. As interest grew, over 250 international visitors came to Saskatchewan to visit this unique, world-class project. The implementation of a monitoring, measurement, and verification program was also undertaken, of which the permanent seismic array is a critical component.

To build this permanent seismic array, six-hundred-and-thirty geophones were installed around the project site.  But what exactly is a geophone?

“Geophones,” says Aquistore’s top research scientist Dr. Don White (Natural Resources Canada), “are very sensitive listening tools. They measure ground vibrations which are used to image the Earth’s structure in a manner similar to medical ultrasound imaging.”  While geophones and seismic surveys have been used for decades to define and illustrate the subsurface of our planet, Aquistore is the first project to implement seismic monitoring of this kind aimed at tracking and observing the movement of CO2.

Installation of this innovative sparse array took place in March of 2012 on a 2.5 x 2.5 km grid. The six-hundred-and-thirty geophones were installed at a depth of 20 m. This installation will serve as both an active and passive source of monitoring and can be activated using various man-made sources of vibrations to monitor activity. Of all available remote monitoring systems, the use of sequential seismic imaging at the Aquistore site will provide the highest definition of CO2 in the subsurface.

This permanent array is already collecting data for Aquistore, allowing the project to establish monitoring baselines before CO2 injection and to track any minute movements of the subsurface. Following the initial installation, a baseline test survey was conducted. Data from each of the six-hundred-and-thirty geophones has been harvested, and the Aquistore team continues to process and analyze its results.

As 2013 continues, Aquistore moves closer to its goal of injecting CO2 , which will be captured at the nearby SaskPower Boundary Dam Power Station and transported via pipeline to the Aquistore site. Once CO2 injection begins, the permanent seismic array and its 630 geophones will listen and observe the CO2 3.4 km below the ground surface. Aquistore’s permanent seismic array is anticipated to provide the clearest and most accurate information possible on the subsurface movement of CO2.

Aquistore and Natural Resources Canada have been working collaboratively, to take advantage of this remarkable technology.  Dr. White and his team have been out in the field again. In the past month, aided by snowmobiles, the seismic team conducted additional baseline field-work outside Estevan. In one test, a group of geophones was lowered to the bottom of the injection well, while a ‘sound source’ was lowered into the observation well. This source produced sound waves which were then picked up by the geophones in the injection well. This allows for a detailed image which shows the geology within the reservoir and the cap rock which seals the injection zone.

A second test of the permanent seismic array was hindered by – what else – the snow. This baseline survey will now take place later in May. These seismic tests are regular occurrence says Dr. White although the schedule will depend on the COinjection schedule: “In general the surveys are repeated after time intervals in which the cumulative amounts of injected CO2 have increased significantly. We anticipate repeating the surveys every 12 months for the first years of monitoring”.

While these geophones continue to listen, the world watches. Aquistore’s seismic program is the first of its kind. As monitoring work continues, Aquistore is attracting interest from research partners, internationally. International visits are beginning again in the coming month. The demonstration of deep saline CO2 storage, economics, and monitoring requirements developed by the Aquistore project are of global interest and applicability.

 As Canada and the world work towards reducing greenhouse gas emissions, projects like Aquistore are more necessary than ever. Aquistore is helping Saskatchewan reduce greenhouse gas emissions and leading the way for CO2 geological storage in Canada and the world. 

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