Mal and all,

By profession I am probably one of the competent people to reply, I am a 
Petroleum and Drilling Engineer working in the service sector of the oil and 
gas industry.

Regarding the cables I can confirm what Gerhard mentions in his mail below, 
these geophones pick up reflections from artificially created noise, mostly 
from explosions or also from vibrating trucks on the surface.

There is, however, the use of VLF in drilling operations. There is a sort of 
Measurement While Drilling technology, which uses low frequency currents to 
transmit data from the drill bit some several thousand meters below the surface 
to the surface. those systems are called EM-MWD, which means electro-magnetic, 
however, is is more an AC modulated DC current that is used to identify and 
demodulate the data. Frequencies here are in the hundreds of Hertz range, and, 
hence, should not be any trouble to our VLF/LF/MF activities.

Also, there are systems used for what we call borehole logging, which are 
sensors that are used in boreholes to determine the formation properties, that 
use frequencies of several hundred kHz, equal to LF or MF. Those are, however, 
injected into the formation way below the surface and we might only be able to 
detect those if a drilling rig is very close to our homes (not completely 
unlikely because several geothermal drilling activities are carried out 
directly in cities and populate areas these days). I know, however, from tests 
we (my company) carried out back in the 80ties, that those signals are 
attenuated some 200 db (!) on their way from the borehole bottom to the surface.

Vy 73

Geri, DK8KW & DI2BO

P.S.: Gerhard, where do you live? I assume the seismic activities near your 
home are carried out for OMV? It's one of my clients and I am in Vienna around 
twice a month.


On 23.08.2012, at 20:37, Gerhard Hickl <[email protected]> wrote:

> Hi Mal!
> 
> I live in an area (very Eastern part of Austria) which has GAS/OIL
> resources. During the past two decades, it was common here to search for
> new sources with the method you described.
> 
> As far as I know, those cables aren't carrying any kind of signal, but
> rather they are used to transfer signals detected by probes
> (microphones) to a central data-processing station.
> 
> The sources of this "noise" detected by the probes could be either
> explosive loads, detonated in drilled holes up to some hundreds of
> meters in depth, or vibrations generated by special machines. Those
> machines are kind of Caterpillars with a big vibrating metal plate at
> the bottom which is transferring mechanical vibrations into the ground.
> 
> From the radiation patterns, picked up by the many probes (microphones)
> which are connected via a mesh of cables, geologists can tell about the
> position of a undiscovered potential Oil/Gas - field.
> 
> So as far as I know and have experienced, there is no threat to our
> activities.
> 
> 73
> OE3GHB
> Gerhard
> 
> 
> 
> 
> Am Donnerstag, den 23.08.2012, 15:13 +0000 schrieb mal hamilton:
>> LF/MF
>> Seemingly some cables are being layed through out some parts of the UK
>> for GAS es  OIL exploration. These cables will will carry a signal to
>> penetrate the earth and detect if gas/oil is below. There will also be
>> some small explosive charges at times in the earth and these will be
>> detected also by the cable and fed to a master station.
>> Does anyone know what frequency is transmitted down these cables or
>> mode of transmission PULSE etc
>> This could be a source of QRM for the LF/MF radio amateur and most
>> people do not know it is taking place and wondering where the QRM is
>> coming from.
>> There will be a network of cables for hundreds of miles lying on
>> fields and ditches etc while the exploration is going on
>> 
>> 
>> de mal/g3kev
>> 
> 
> 
>