Water at a depth 300-400m

[panku44]

Hi,
What methods are most effective for finding water at a depth of 300-400 m ?? It is possible at all??
Thanks for any sugestions

[geophix]

I would say it's possible with some geophysical methods, such as nuclear magnetic resonance (NMR) and magnetotelluric (MT). They can achieve great investigation depths, of course depending on a lot of factors such as geological settings and noise levels, etc. I am not sure how deep they can reach exactly, but it's worth to take a look if you have a potential project at hand. Another apparent method is seismic reflection, which involves more knowledge about local geology.

[chrisvecan]

NMR is a great method because it detects water directly without ambiguity as in other methods. However, its investigation depth can hardly reach more than 150m based on current technologies. Hopefully the hardware and software development in the future could improve the investigation depth greatly. The culture noise is a big problem for NMR.

[ncoord]

DC electrical resistivity can be used too. The instruments used in the mining industry are generally much more powerful than those used in engineering applications. The investigation depth can reach more than 600m.

[panku44]

NMR is a great method because it detects water directly without ambiguity as in other methods. However, its investigation depth can hardly reach more than 150m based on current technologies. Hopefully the hardware and software development in the future could improve the investigation depth greatly. The culture noise is a big problem for NMR.

Could you give me more info about this method (NMR) - How looks survey, its posible to buy , where??
All best

[chrisvecan]

Could you give me more info about this method (NMR) - How looks survey, its posible to buy , where??
All best

Check this link:
http://www.vista-clara.com/instruments_gmr.html

[geophix]

NUMIS from Iris instruments
http://www.geomatrix.co.uk/datasheets/Numis%20Poly.pdf

If you are interested, there is a full day course in this April at SAGEEP:
http://www.eegs.org/AnnualMeetingSAGEEP ... shops.aspx

[gouezouille]

Depend the accessibility of the sounding area. If you are looking for water in desertic area, without space limits, you can try an electrical resistivity sounding but with electrode spacing biger than 2 km.
Otherwise I would try TDEM, using big loops.
For PMR (MNR) the small expenrience I have with the numis show me that this method is very interesting in hydrogeophysical prospecting. In the case of low EM noise, you can estimate porosity and water moisture (water quantity). In some media, sand, porous limestone, ... you can estimate hydraulic conductivity (k) too !!!!

However I 'm afraid that 400 meters deep is too much...

[marken]

As a common sense, I usually divide the investigation depths claimed by the manufacturers by 2 or more as my safe investigation depths.

[Shogun]

It would be helpful to know if you expect to have a resistivity contrast between the aquifer and the surrounding rock. If there is a significant contrast, I would say TDEM or a pole-dipole ERI survey would be the best bets. At those depths, you can expect quite a bit of uncertainty in your data, especially the depth to the target, but both those techniques could be good prospecting tools. Follow up drilling and borehole logging would be the natural next step.

If there's only a small resistivity contrast, I would try reflection seismic. It won't directly detect water, but it can identify the increase in porosity you would expect from an aquifer zone.

[ncoord]

Any recommendations for the instruments doing TDEM?

[Shogun]

Any recommendations for the instruments doing TDEM?

There are a bunch of manufacturers but Geonics is a well-recognized one. They make some higher power transmitters for deeper investigations such as 300-400m. One thing to realize is to look down that deep, you have to use large transmitter loops, maybe 200m in diameter or more depending on geology. The area has to be relatively flat and free of surface infrastructure (ie pipelines, powerlines etc.). Vertical resolution is maybe 10-20% of the transmitter diameter.

If the surface conditions don't allow for TDEM, you'd be better off with ERI or reflection seismic.

[ncoord]

Thanks! I didn't know Geonics makes such instruments.

[limestone]

If the ground surface has a strong topography, is this going to be a problem for TDEM? I heard a company using terraTEM, is it a TDEM instrument?

[Shogun]

Yes strong topography can be a problem for TDEM. I believe it comes down to the assumptions that a) the earth is generally layered and flat b) the transmitter loop is a perfect square, with each side exactly the same length as the others.

Those 2 assumptions could be very wrong in the case of strong topography, especially if one side of the square is straight and flat and the other side is going up and down through small ravines and hills. Also strong topography is usually accompanied by strong surface inhomogeneity, which can also strongly affect the measurements (flat layer assumption is violated by surface inhomogeneity). TDEM data has to be inverted in order to be interpreted effectively, and anytime you are dealing with inversion and the problem of non-uniqueness, small deviations from your original assumptions can get blown up into wide variations in the final earth models after the inversion process. I should point out that it is perfectly fine to have the transmitter loop on the side of a hill or slope, where one side of the square is at a higher elevation than the other, as long as the loop is still a square and the slope is a fairly constant angle.

One other interesting thing about TDEM that I forgot to mention is: it is far better at defining a conductor inside a resistor than a resistor inside a conductor. Ok, go think about that for a while and let's see if anyone can come up with the reason why!!!

[ncoord]

I think a resistor inside a conductor has little effect on the overall reading, while a conductor inside a resistor will give a strong anomaly against the background readings. If there are no noises at all, the anomalies in both situations can be detected. With certain amount of noises, strong anomalies are easier to detect.

[alexy]

The most effective NMR method for the direct detection of thermal,-drinking water reserves, hydrocarbon reservoirs and minerals to deep depth of 5 km, indicated on the links:

NMR testing, exploration, presentation http://www.mediafire.com/?1ofofuei4uwx683
NMR_exploration,presentation_water_ project http://www.mediafire.com/?4rqp8mj7bq22amp

[ikbal173]

Great.. is there any success story after using the NMR method to detect groundwater at > 150 m depth?

[alexy]

UAE 2007 - 7 underground fresh water flows identified and delineated
UAE 2009 - The territory of the UAE and adjacent countries has been investigated. The source of the formation of deep underground fresh waters of the Arabian Peninsula is identified
Mauritania 2010 - A powerful underground flow of fresh water was identified. A well was drilled with a depth of 150 m with a flow rate of 25 l / sec.
Mongolia 2013 - Regional and detailed survey of the Gobi desert area. Underground fresh water flow was revealed. Well with depth of 300m and flow rate of 7 l/sec was drilled.
Mongolia 2014 - Drilled well in the area of Dalanzadgad city with a depth of 200m and a flow rate of 7 l/sec.
Cyprus 2015 - Underground fresh water flow was detected and delineated. A 200m deep well with 7 l/sec flow rate was drilled.
Ethiopia 2016 - Regional and detailed survey of a 1000 sq. km plot in the Danakil desert. A 190m deep well with 20 l/sec flow rate was drilled.
Oman 2019- Detailed survey of the site in the Wakhiba desert. Underground flow with water horizons at depths from 95 to 260m was detected and applied.
Ukraine 2007–2019 - Over 1,200 sq. km of various plots were surveyed. Over 120 wells were drilled. Maximum depth of wells is 950m with 7 l/sec flow rate.

[Marie143]

Drilling,drywall repair contractors in fort worth texas boreholes, and using a water well drilling rig are effective methods for finding water at depths of 300-400m. It is possible but may require specialized equipment and resources.

[alexy]

Drilling,drywall repair contractors in fort worth texas boreholes, and using a water well drilling rig are effective methods for finding water at depths of 300-400m. It is possible but may require specialized equipment and resources.

Do you look for deep underground accumulations and water flows "by borehole drilling"?
This is a very expensive method. Only NMR directly will find it almost for free.