A step change in seismic imaging using a unique ghost free. What is the difference between ghost reflection and. Geo expro broadband seismic technology and beyond, part ii. Seismic exploration software tools seismic modeling and imaging and papers on their application. Simple being free of charge is not sufficientsee gratis versus libre. Seismic processing and imaging gain deeper insight with the industrys most accurate subsurface imaging tools. The new system is based on a time and depth variable source combined with a dualsensor streamer. If the source is towed at a depth of 9m, the phase reversed water surface ghost reflection is added to the source pulse with a travel time delay of 12ms. The reflection from the flat interface produces a curved series of arrivals on the seismic traces since it takes longer to travel to the far offsets than the near offsets.
At one time, seismic processing required sending information to a distant computer lab for analysis. Pgs uses a deghosting solution based on the waveequation, where a forward operator that describes how all seismic events that are reflected by the seasurface will create a ghost, is inverted for. Generally speaking, the inverse filter of the ghost operator gn is a filter g. Oct 30, 2019 a ghost is a multiple reflection that is a bounce off of the surface. One way to remove ghost effects from acquired seismic data is to calculate, and then apply to the received seismic data, an inverse filter of the ghost models in equation 2. Apr 22, 2020 radexpro is a seismic processing software on windows. Our smooth inversion tomographic method is based on physically realistic modeling of first break propagation for pwave and swave surveys. This paper describes the unique ghost free acquisition system based on the dualsensor streamer combined with a ghost free time and depth distributed source. A ghost is a multiple reflection that is a bounce off of the surface. The effect of the sea or land surface is a wellknown obstacle in seismic exploration and has been addressed since the outset of reflection seismology leet, 1937.
The size and scale of seismic surveys has increased alongside the significant increases in computer power. For constant depth recordings, a spectral division operator is used. Seismic 2d reflection processing and interpretation of. Ghost events are generated at both the shot and receiver positions, due to downward reflection from the sea surface. The ghost near the source combines with the source signal to.
Design and analysis of 3d seismic data acquisition. The reader interested in freeware just free of charge software is referred to the list of freeware geophysics software. Deghosting and designature removing the seismic ghost. The maximum power of the signals, which is full black, indicates the frequency band over which the stacked section has good spectral power margrave,1995. This is the reflection that takes place when the energy traveling upward from the shot is reflected downward by the base of the weathered zone or by the earths surface.
Ixrefrax is the successor to gremix and firstpix, our dos based seismic refraction data processing and interpretation system. A unique ghost free source and receiver system has been demonstrated through processing to deliver broadband seismic data with a frequency content of 2. List of free geophysics software project gutenberg self. A variant of seismic reflection used at the surface of water bodies is subbottom profiling or imaging. A simple 2conductor wire connects the geophones to the computer. It is well suited for indepth hruhr marine seismic processing, realtime marine 2d3d seismic qc, onboard fast track processing, land and marine offline seismic qc, complete processing of nearsurface seismic data reflection, refraction, tomography, masw and vsp processing.
A seismic refraction or seismic reflection line is a set of seismographs usually lined up along the earths surface to record seismic waves generated by an explosion for the purpose of recording reflections and refractions of these waves from velocity discontinuities within the earth. Processing was done using mainly open source software seismic unix. It can be used to derive important details about the geometry of structures and their physical properties. A goal of seismic data processing is to enhance primary reflections, which are then interpreted as subsurface interfaces. Their latest funding was raised on dec 19, 2018 from a series e round. There are processing methods to address the ghost too, but these are still estimating completing the spectrum in various ways. Key seismic has implemented a proprietary technique for shot and receiver deghosting of marine seismic, which has been successfully applied on a large volume of east coast canadian data. The technique requires plotting points and eliminating interference. Convolution use the sonic and density logs to compute an impedance log calculate the reflection coefficients convolve our pulse with the seismic reflectivity sum the individual wavelets to get the synthetic seismic trace seismic ties compare well data to seismic data. The seismic volume is the f3 block in the north sea, which is publicly available via dgbs seismic repository. Figure 1 illustration of marine seismic ghost reflections.
In most software the setting up of a 2d marine geometry is pretty simple you assume the streamer is being towed directly behind the boat and so the offset is a simple function of the channel number, and the cdp number is a function of the shot number. We forward model refraction, transmission and diffraction lecomte, 2000. A step change in seismic imaging using a unique ghost. May 19, 20 removing the ghost is a different matter. Sign up for free to unlock and follow the latest funding activities. The time delay therefore is given by t 2d cosqc, where d is the source depth, c is the sound of speed in water, and q is the offset angle of the initial downwards primary pulse measured from the vertical axis. Spectral analysis of a ghost crewes research report volume 10 1998 43 figure 7 shows the fx amplitude spectra of prestack tvsw stack for both 18 m and 9 m data. Geometrically, the source ghost appears to originate from the mirror image of the seismic source. Seismic refraction is a geophysical principle governed by snells law. The joint deconvolution approach soubaras, 2012 does not just remove the receiver ghost effect, but at the same time, the ghost reflection is migrated at its right location. For example, the license may rule out use by certain people or for certain purposes, e. This is a series of three lab exercises integrating seismic interpretation and sedimentary geology. The joint deconvolution approach soubaras, 2012 does not just remove the receiver ghost effect, but at the same time, the ghost reflection is. Spex eliminates the need to pick detailed velocity functions, and also provides a unique view of the.
List of free geophysics software this is a list of free and open source software for geophysical data processing and interpretation. Major fields of application of seismic reflection include. Seismic reflection data geol493k west virginia university. Designed for windows 9x and nt download the software.
The following projects have unknown licensing, licenses which place some restriction on use or redistribution, or depend on nonopensource software like matlab, and therefore do not meet the open source definition from the open source initiative. Reflection seismology, more commonly referred to as seismic reflection or abbreviated to seismic within the hydrocarbon industry, is used by petroleum geologists and geophysicists to map and interpret potential petroleum reservoirs. In marine work a source is detonated slightly below the water surface. Seismic reflection methods environmental geophysics us epa. Van melle and weatherburn 1953 dubbed the reflections from energy initially reflected above the level of the source, by optical analogy, ghosts. The ghosts are created by reflection of the seismic signal with polarity change off the sea surface, near the source and the receivers. The next thing we need to do is to sort out the geometry, so that we can compare what we think the geometry should be to the actual data. Enhanced imaging using broadband seismic data processing. A method for use in improving marine seismic data quality includes. Event and ray path marked 1 is an illustration of the primary reflection, 2 is an illustra tion of the source ghost, 3 is an illustration of the receiver ghost and 4 is an illustration of the ghost reflection recorded due to source and receiver ghost interaction. Seismic reflection is the most widely used geophysical technique. Us9594180b2 removing ghost reflections from marine seismic. Ghosts on seismic data exhibit themselves as notches in.
It is a delayed source pulse that follows after the actual source pulse, with a delay equal to the time from source to surface. Seismic refraction processing and interpretation using grm. Seismic data processing involves the compilation, organization, and conversion of wave signals into a visual map of the areas below the surface of the earth. This procedure makes rapid, continuous reflection soundings of the units below. Apr 24, 2020 deconvolution, in seismic data processing, shortens reflection waves and reduces the ghost effect that can might occur because of instrumentation, reverberations, or multiple reflections. Reflection seismology or seismic reflection is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the earths subsurface from reflected seismic waves.
This hyperbolic curve shown in the dotted red line is called the normal moveout curve or nmo and is related to travel time, offset and velocity of the medium as shown by. Deghosting and designature removing the seismic ghost and. Field procedures the optimum offset technique is the simplest form of shallow seismic reflection profiling possible. This clip explains how the seismic technology works and. The filtering effect of the ghost reflection limits the useable bandwidth to a zone between 0 and 80hz.
A shortpath multiple, or a spurious reflection that occurs when seismic energy initially reverberates upward from the shallow subsurface and then is reflected downward, such as at the base of weathering or between sources and receivers and the sea surface. The aim of this work was to use twodimensional reflection seismic processing methods to refraction seismic data collected from the onkalo area in year 2002, and to locate gently dipping reflectors from the stacked sections. A method, stored in a memory and executing on a processor, for attenuating ghost reflections in seismic trace data, said method comprising. This is a list of free and open source software for geophysical data processing and interpretation.
This function generally shows more clearly defined layers. The process derives a recursive filter which is then applied to the preprocessed seismic data to create a ghostfree data. The primary seismic wavelet propagates downward but there is an upward propagating wave that reflects from the water surface and then propagates downward. The seismic unified data system suds is a foundation suitable for such teamwork in all types of seismic processing, from studies of earthquakes to discrimination of explosions to reflection and. Radexpro is a seismic processing software on windows. The list is split into broad categories, depending on the intended use of the software and its scope of functionality.
Each lab uses freely available software from dgb earth sciences, opendtect. Near surface exploration seismic systems, sometimes called engineering seismographs, are used for earthquake site response, rippability surveys, depthtobedrock, groundwater exploration, geologic hazards, shallow reflection surveys, shear wave surveys and multichannel analysis of surface waves masw. Currently, laptop computers equipped with seismic software allow. Reflexw software, according to selected module, covers complete range of wave data seismic, gpr,ultrasound and their processing throgh different geometry assemblings such as refraction seismic, reflection seismic, surface investigations and borehole crosshole, tomography and combination of borehole and surface measurements. The advantage of this technique is the ability to tow the seismic source on a sled or catamaran and to tow the line of hydrophones.
What is the difference between ghost reflection and multiple. Ghost events are generated at both the shot and receiver positions, due. Having used radexpro professional for diverse nearsurface research projects we can say that this software package does a great job. The seismic energy emitted by the seismic sources consists of two constituents. Orfeus maintains a seismological software library ssl with web and ftp site links. The amplitude spectrum of this modified source pulse is shown in figure 3. Definition of ghost reflection in the seismic reflection method, a special type of multiple reflection. Reflection exploration is a ukbased seismic processing and software development company we produce seismic processing software for 64bit windows the hotshot processing system and the spex interactive velocity analysis and stack program hotshot is a fully featured processing system. Pdf processing seismic data with open source software. Notice that free and opensource requires that the source code is available.
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