This tutorial is intended for the users, who begin to process seismic reflection cdp data in the radexpro plus program. Seismic reflection an overview sciencedirect topics. This deals only with the arrival times of the seismic wavelets in the input gathers for given source and receiver locations, and takes no account of the amplitude and phase of the data. Depends on changes in velocity, density, and poissons ratio i. Glossary of seismic terminology acceleration the time rate of velocity change, commonly measured in g an acceleration of 32 ftsecsec or 980 cmsecsec gravity constant on earth. If the wave reaches an interface, some of the energy will be transmitted, and some will be reflected. The term chronostratigraphic defines this type of seismic reflection event. Moveout click on an image for a high resolution adobe acrobat pdf version of the figure. Geophysics seismic processing basic theory seismic acquisition and data processing using seismic software promax for advanced geosciences in seismic exploration by oil and gas company. 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. Seismic reflection method ground geophysics techniques. Reflection seismology a seismic recording system comprises a sensor or receiver that converts the seismic wave into an electrical signal, an analogdigital converter and a recorder. This procedure makes rapid, continuous reflection soundings of the units below. The course covers the history of activesource seismic methods.
For free space, the onedimensional wave equation is derived. Reflection seismic imaging uses reflected energy to construct an image of the subsurface to investigate the underlying structure and stratigraphy. Seismic basics in 5 pages university of saskatchewan. Special thanks to anna courtier at james madison university and chris thaxton in the department of physics and astronomy at appalachian state university. Basic geophysics, seismic fundamentals and 3d seismic. Introduction to seismic method utilized during survey. Seismic reflection methods applied to engineering, environmental. A fundamental thesis of seismic stratigraphy is that a seismic reflection event follows an impedance contrast associated with a stratal surface. A short course in seismic reflection profiling theory, wave propagation in layered media, data acquisition, processing, interpretation prof.
Geologists, geophysicists and engineers who are unfamiliar with seismic acquisition and processing techniques and wish to learn about the steps involved in the acquisition of seismic data and the creation. Basic geophysics, seismic fundamentals and 3d seismic exploration by r. Theory of daylightinterferometric imaging tutorial. The proper assignment of these geometrical properties is fundamental to all that follows. Reflection seismology is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the earths subsurface from.
Seismic 2d reflection processing and interpretation of. Seismic studies to represent reliably the subsurface geology, require. Deep seismic reflection surveying is the most advanced technique in geophysics today, thanks to its application on a huge scale for oil and gas exploration. For example, the contact between sand with water saturation and sand with certain gas saturation gives a high rc that produces an amplitude. Basics of seismic interpretation the lesson uses the basics seismic reflection principles, and allows the student to apply them to interpret a geologic framework, conduct a data analysis, prospect for hydrocarbons, and then assess whether the basin should be bid on and provide an economic analysis. Fred schroeder, retired from exxonexxonmobil presented on august 24, 2017. Seismic attribute analysis can extract information from seismic data that is, otherwise, hidden in the data and have been used to identify prospects, ascertain depositional environments. There are three primary steps in processing seismic data deconvolution, stacking, and migration, in. Seismic data processing geos 469569 spring 2006 geos 469569 is a mix of digital filtering theory and practical applications of digital techniques to assemble and enhance images of subsurface geology. This basic sequence now is described to gain an overall understanding of each step. Black abstract shallow seismic reflection surveys can assist in deter mination of velocity andor thickness variations in near surface layers. Seismic interpretation an overview sciencedirect topics.
The seismic reflection data portal of the mgds serves field data from multichannel seismic expeditions over the past 20 years as well as a large number of legacy single channel seismic images from expeditions of the rv. The most common sensors in marine seismics are hydrophones, which are piezoelectric elements that produce an electric potential. Static corrections from shallow reflection surveys d. In year 2001 olkiluoto was selected for the site of final disposal. Basic theory in reflection seismology, volume 1 1st edition. Seismic resolution is controlled by the bandwidth of the signal, which is typically f30140 hz.
The variation in the amplitude of a seismic reflection with angle of incidence or sourcegeophone distance. If you continue browsing the site, you agree to the use of cookies on this website. The wave phenomena occurring at a boundary between two layers are discussed, such as snells law, re. Portions of the lecture notes posted here were derived from their materials. This method of seismic reflection data is widely used to infer the presence of hydrocarbons.
Seismic reflection is ideal for mapping geology at depths exceeding 50 m. Aaron micallef, in developments in earth surface processes, 2011. Used in the fields of engineering geology, geotechnical engineering and exploration geophysics, seismic refraction traverses seismic lines are performed using a seismographs andor geophones, in an array and an energy source. Seismic reflection methods environmental geophysics us epa. Introduction to industry seismic reflection methods and. Seismic 2d reflection processing and interpretation of shallow refraction data abstract posiva oy takes care of the final disposal of spent nuclear fuel in finland. The purpose of processing cdp seismic reflection data is to enhance the reflections at the expense of everything else. 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. Basics of seismic interpretation incorporated research. Seismic energy is detected on land by using devices called geophones, which react to onsite ground motions. Basic principles of the seismic method tu delft ocw.
For seismicexploration purposes, where measurements are taking place at the surface, the different arrivals of direct waves, reflected waves and refractedhead. Seismic attributes and their applications in seismic. Note that the waves travels from medium 1 into medium 2. Currently construction of the underground research facility, onkalo, is going on at the olkiluoto site. Reflection frequencies decrease with depth because of. All standard stages of basic cdp processing are discussed, from the introduction of geometry to stacking, that is the socalled minimal processing sequence. Seismic reflection surveys, on the other hand, detect boundaries between different kinds of rocks. Introduction to petroleum geology and geophysics geophysical methods in hydrocarbon exploration. The sense of the impedance contrast determines the polarity of the seismic reflection, so that the top and base reflections for a sand reservoir encased in shale are. Seismic rays are used instead of the wave front to describe the wave propagation. Basics seismic reflection events are caused by the impedance contrasts at layer interfaces. Hence it falls into the category of the highfrequency.
Tutorial on seismic reflection cdp data processing in the. The most important information on the constitution of the earths interior has been obtained from studies of seismic body waves longitudinal and. This course is an overview of reflection seismic methods and their applications as practiced by the resource, environmental and other industries and by agencies such as the usgs. Microsoft powerpoint introduction to petroleum geology and geophysics. Moveout click on an image for a highresolution adobe acrobat pdf version of the figure. The measured time is known as the two way time twt. Seismic refraction is a geophysical principle governed by snells law.
Basics of seismic interpretation slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. A variant of seismic reflection used at the surface of water bodies is subbottom profiling or imaging. In the earth, seismic waves can propagate as longitudinal p or as shear s waves. Seismic imaging can provide information about geologic structure and stratigraphy including bed. Here the reflection seismic method is adequate and offers much more details. Basic principles of the seismic method in this chapter we introduce the basic notion of seismic waves. The general principle involves sending artificially generated acoustic waves down the water column and into the seafloor, where the different structures. For reflection seismology, the end product is a record section from a collection of wiggly traces that are recorded in the field from which information about the. Raypaths are lines that show the direction that the seismic wave is propagating. Since the introduction of digital recording, a routine sequence in seismic data processing has evolved. There are a wide variety of filtering, display, and static correction techniques that can be employed to improve the quality of the reflections.
See mathematical details in the seismic basics in 5 pages on page 5. Jones abstract conventional seismic data processing, whether it be prestack data conditioning or migration, is designed with the theory of pwave reflected energy inmind, for travel paths involving only a single reflection. Seismic reflection is a method of exploration geophysics that provides information about the subsurface structure of the seafloor. High resolution seismic reflection practical basis wgeosoft. Accelerogram the record from an accelerograph showing acceleration as a function of time. Seismic attributes are the components of the seismic data, which are obtained by measurement, computation, and other methods from the seismic data. Static corrections to seismic reflection data compensate for velocity and thickness variations within. In seismic interpretation, the reflection coefficient rc of two different rocks depends on the difference between their seismic impedance and this depends mostly on the pwave velocity in the rock. Use geomapapp to explore processed reflection sections from multi channel seismic surveys, digitize horizons and download profiles. Seismic amplitudeversus offset avo analysis has been a powerful geophysical method in aiding the direct detection of gas from seismic records. Tutorial on how to use mgds tools for seismic reflection data. Seismic reflection events are caused by the impedance contrasts at layer interfaces having a minimum width fresnel zone. Digital filtering theory applies to virtually any sampled information in time e.
Reflections, which arrive later than the refractions in the. It is rare that the correctness or incorrectness of an interpretation can be ascertained, because the actual geology is rarely known in enough detail. Because the shallow seismic reflection method has not been. Seismic interpretation, whether for hydrocarbon exploration or geotechnical studies, is the determination of the geological significance of seismic data. Every point on the wave front is a source of a new wave that travels out of it in the form of spherical shells. Database buildingthe myriad of numbers on field tape must each be uniquely related to shot and receiver positions on the surface of the earth, an elapsed time after the shot that originated the reflection or echo traveltime, and a reflection point on the subsurface of the earth at any traveltime.
The method requires a controlled seismic source of energy, such as dynamite or tovex blast, a specialized air gun or a seismic vibrator, commonly known by the trademark name vibroseis. The unofficial seisx web site, a self help tutorial on how to start seisx, import. Seismic studies to represent reliably the subsurface geology, require quality data, which depend on signaltonoise ratio and resolution, the latter being the ability to image thin geologic features separately. The material in this volume provides the basic theory necessary to understand the principles behind imaging the subsurface of the earth using reflection and refraction seismology.