New method gives way to non-invasive subsurface data

Mar 11, 2014 by Geoff Vivian
This method could be used in place of having to drill a ‘monitoring well’ as done in conventional cross-well surveys. Credit: Eric Hodel

A hydro-geologist has found an inexpensive, high-quality three-dimensional imaging method for aquifers and other below-ground features.

Conventional cross-well surveys require a monitoring bore containing sensors, and another source well in which a seismic shock is produced.

Now, PhD student Majed Al Malki has eliminated the need for a dedicated monitoring well, if two bores are already available.

He developed a method whereby he placed sensors in two existing vertical wells and created a shock wave at a fixed point on the surface.

He then measured and interpreted the differences between signals received at varying depths in the two wells to produce an image of the geology in between.

"When compared to conventional walkaway vertical seismic profiling, the only additional effort required to complete dual-well walkaway vertical seismic profiling is the deployment of in the second well," Dr Al Malki says.

He conducted the experiments at the Water Corporation's Mirrabooka aquifer storage and recovery site during his PhD studies, under the supervision of Curtin University Associate Professor Brett Harris.

"[This project] was looking at banking excess water in the shallow aquifers into deeper aquifers that are slightly depleted," Prof Harris says.

"The main thing was to look for ways of characterising the rock around those formations."

He says they used a 1000kg piece of concrete, dropped from a Bobcat, as a weight-drop source of .

"[The] surface source bangs the ground on, in our case, about 150 locations and then we use the energy as it propagates through the earth between the two wells.

"The path of the seismic energy goes from one well to the other well but all at different angles from the different source positions on the surface."

He says this allows them to reconstruct sub-surface source positions in the well nearest to the seismic energy source.

"It looks like there was a source there without you actually having to put one there," he says.

"That information can be used to actually reconstruct what a source would look like if it were located underground."

He says the beauty of this method is that there is no need to place a seismic shock source inside a purpose-drilled hole.

"It's really a non-invasive method of understanding what the distribution of the key interfaces are," Prof Harris says.

He says the technique could be applied to assess underground environments for petroleum, geothermal and groundwater reserves and carbon storage sites.

Explore further: Seismic network detects landslides on broad area scale

More information: "Majed Almalki, Brett Harris, J. Christian Dupuis, Field and synthetic experiments for virtual source crosswell tomography in vertical wells: Perth Basin, Western Australia," Journal of Applied Geophysics, Volume 98, November 2013, Pages 144-159, ISSN 0926-9851, dx.doi.org/10.1016/j.jappgeo.2013.08.021.

add to favorites email to friend print save as pdf

Related Stories

Seismic network detects landslides on broad area scale

Oct 09, 2013

From 1999 to 2006, Taiwan's Chenyoulan watershed experienced 48,000 landslides, rock avalanches, and other geomorphic events, the bulk of which are thought to be triggered by the powerful tropical cyclones that batter the ...

Hydro-fracking: Fact vs. fiction

Nov 05, 2012

In communities across the U.S., people are hearing more and more about a controversial oil and gas extraction technique called hydraulic fracturing – aka, hydro-fracking. Controversies pivot on some basic questions: Can ...

3-D Earth model more accurately pinpoints explosions

Oct 28, 2013

During the Cold War, U.S. and international monitoring agencies could detect nuclear tests and measure their size. Today, they seek to pinpoint much smaller explosives tests. Under the sponsorship of the ...

Urbanization exposes French cities to greater seismic risk

Mar 07, 2014

French researchers have looked into data mining to develop a method for extracting information on the vulnerability of cities in regions of moderate risk, creating a proxy for assessing the probable resilience of buildings ...

Homing in on a potential pre-quake signal

Aug 02, 2012

In a new analysis of the 2004 magnitude 6.0 Parkfield earthquake in California, David Schaff suggests some limits on how changes measured by ambient seismic noise could be used as a pre-earthquake signal.

Recommended for you

Kiribati leader visits Arctic on climate mission

Sep 20, 2014

Fearing that his Pacific island nation could be swallowed by a rising ocean, the president of Kiribati says a visit to the melting Arctic has helped him appreciate the scale of the threat.

NASA catches a weaker Edouard, headed toward Azores

Sep 19, 2014

NASA's Aqua satellite passed over the Atlantic Ocean and captured a picture of Tropical Storm Edouard as it continues to weaken. The National Hurricane Center expects Edouard to affect the western Azores ...

User comments : 0