Tuesday, August 01, 2006


Are blasting mats used for offshore oil seismic exploration?

Here is a chart of all of the Seismic actiity done on the continental shelf over the past few years.

I was amazed at the amount. Now I don't know anything about underwater oil exploration but I am familiar with explosives, not so much so under water but the properties are the same just the environment is different. That is to say explosives utilized under water have much more impact than when used in open air because the shock wave is so much more contained. In fact underwater explosions have a double impact kinda like the effect of lightning. When the air is forced out of the area where the lightning passes and then the air rushes back in to cause the thunder clap from the air filling the void.

Enough back ground I need some answers. What I was wondering is during all of this seismic (another way of saying controled explosions to send out shock waves so the returning waves can be measure to determine the density of the earth crust, layers and mantle to see if the geology is conducive to oil deposits) testing was any form of blasting mat used to help mitigate the effect explosions were having on the natural fish habitat? Or for that matter was it even necessary due to the size of the explosive charge being used? I imagine if the charge was only in the 1 lb range it wouldn't necesarily be needed because the shock wave shouldn't have an effect on much more than a 100 metres in circumference (speculating here).

This also is subjective to the amount of testing and frequency. If a charge is let of every 100 metres then some form of blasting mat should have to be used to mitigate the effects on the environment and species in the area.

Explosives have an increased effect 10 fold in underwater usage?

Even if they used shaped directional charges it would limit somewhat the effects on the fish habitat or the charges were somehow buried under the sea bed so as to lessen the effect on the surrounding water.

Then there is the ensuing massive silt cloud which when carried by currents and tides could spread over I fear to guess 100's of kilometres. If this takes place during spawning time it could kill off hundreds of thousands of prospective fish from being hatched due to the smothering effects of the settling silt. Not unlike what is now highly illegal in construction near or around spawning brooks and rivers. To my knowledge I have never heard of any time frame which is blocked out as off limits because it is a spawning time to protect the breeding habitat.

Sorry I have more questions than answers but they needed to be asked when you consider the state of our continental shelf and fishing industry.

Map of wells drilled.

Map and chart come from the CNLOPB web site.

Here is a web site which explains the effects of underwater explosions through diagrams. Very simplistic military application used as modeling.
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