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A polyhedral and mechanically isolated seismic sensor package

IP.com Disclosure Number: IPCOM000245612D
Publication Date: 2016-Mar-22
Document File: 5 page(s) / 291K

Publishing Venue

The IP.com Prior Art Database

Abstract

The impact of a droplet of water or a grain of sand on the package containing a seismic sensor generates an electrical signal that because it is not due to a seismic wavefield propagating in the earth's interior is referred to as noise. The magnitude of this noise depends on the frequency response of the system composed by the sensor, the box that contains the sensor, any other equipment connected to the box and the elastic properties of the ground below or surrounding the box. If all the components of the system remain the same, the effect of different types of sensors can be analyzed.

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Title: A polyhedral and mechanically isolated seismic sensor package

SUMMARY

This invention disclosure related to onshore seismic acquisition in general and on an autonomous sensor in particular.

PRIOR ART

It is well know that the impact of droplets of water on a seismic sensor generates noise. It has also been recognized (e.g. Cooper, 2012) that this effect is more severe on sensors based upon Micro Electro Mechanical Systems (MEMS) because of their broadband frequency response. It is also well known that wind and other forms of airborne energy generate noise in seismic sensors.

DESCRIPTION OF THE INVENTION

The impact of a droplet of water or a grain of sand on the package containing a seismic sensor generates an electrical signal that because it is not due to a seismic wavefield propagating in the earth's interior is referred to as noise. The magnitude of this noise


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depends on the frequency response of the system composed by the sensor, the box that contains the sensor, any other equipment connected to the box and the elastic properties of the ground below or surrounding the box. If all the components of the system remain the same, the effect of different types of sensors can be analyzed.

Seismic sensors based on a coil moving in a magnetic field (geophones) have been used in seismic exploration for many years. The magnitude response of a geophone rolls off rapidly above a frequency that depends on the model. Seismic sensors based upon Micro Electro Mechanical Systems (MEMS) technology have a broader frequency response. Moreover, they are often contained in boxes that are smaller than those used for traditional geophones. The complete system composed by a MEMS sensor and his package has therefore a broader frequency response than traditional geophones.

The impact of a water droplet generates a very wide range of frequencies and therefore can overdrive a MEMS sensor more easily than a coil based geophone. It should be noted that digital filters can filter out the recorded and digitized noise only if its amplitude does not exceed the sensor full scale.

The sensitivity to droplets of water and sand grains can be reduced by using a big and heavy box that attenuates the low frequencies but this is not practical. The alternative disclosed here is a rugose cover with a polyhedral shape that reduces the effect of the droplet impact. The effect of the impact will then be further reduced by utilizing a hydrophobic coating applied to the polyhedral surface.

Airborne propagating energy (e.g. wind and airwaves produced by seismic sources) i...