Borehole seismic methods largely fall into two categories, namely, crosshole seismics and seismic tomography. Silixas arrayseis service improves ultimate recovery and enables efficient decision making by providing highresolution seismic data throughout the life of well the intelligent distributed acoustic sensor, when coupled to an optical fibre, provides a versatile seismic acquisition platform capable of meeting many borehole seismic objectives. Downhole seismic source software free download downhole. In the downhole technique the seismic source is on the surface, and a threecomponent borehole geophone is placed inside the borehole at different depths. Astm d740008 standard test methods for downhole seismic. The downhole seismic method dh measures the time taken for the p and s waves to move between a seismic source located on the surface of. The seismic downhole method is part with the crosshole of the borehole seismic surveys. Comparison of mean shear wave velocity of the top 30 m. Deep downhole seismic testing for earthquake engineering.
Secondly, down hole seismic is to get bearing capacity parameter in relation to engineering structure when the earthquake happened. Seismic survey is the geophysical method, which is most closely related to rock and soil. The software allows the processing of downhole seismic tests for the p waves and s waves using the direct method and the interval method. Two methods are discussed, which include using either one or two downhole sensors receivers. The main difference between them is the location of the geophones and the seismic source. Invariant are requirements to measure both p and s waves and to use a reversible source to aid in. The downhole receiver s may be positioned at selected test depths in a borehole or advanced as. The equipment and procedures comply with astm d 7400 08, standard test methods for downhole seismic testing.
Us4974671a downhole seismic source with containment. Basic principles of the seismic method in this chapter we introduce the basic notion of seismic waves. Pdf surface and downhole shear wave seismic methods for thick. A sleeve surrounds this section of the drill pipe and includes a cam follower, a. The seismic waves can be denoted as p v or p z for a downward propagating compression wave and as s vh or s zx for downward propagating and horizontally polarized shear wave. Downhole seismic test is an insitu test and determine the velocity of primary p and secondary s seismic waves to provide the elastic soil parameters. Downhole receivers are used to detect the arrival of the seismic wave train.
Fugro is proficient in installing and operating a vast array of permanent borehole instrumentation, including standpipes for gas, water or leachate monitoring and ground movement monitoring, such as inclinometers and magnetic extensometers. Up hole survey, seismic refraction, pwave velocity, weathering layer, consolidated layer. Seismic exploration is divided into refraction and reflection surveys, depending on whether the predominant portion of the seismic waves travel is ho. This report discusses a method for interpreting a layered slowness or velocity model from surfacesource downhole seismic data originally presented by boore 2003.
In ps pile testing, one relies on identifying direct arrival. More recently, an astm standard for downhole shear wavetesting has been published, and there may be some choice of methods. The wave phenomena occurring at a boundary between two layers are discussed, such as snells. Seisimager downhole manual, 20, windows software for analysis of downhole. This paper describes the downhole method commonly used to. Downhole seismic testing downhole seismic testing dst was conducted using a system comprising a surface source a steel ibeam and hammer, a downhole tool equipped with a triaxial geophone package, and a seismograph figure 1. Application of seismic methods for geotechnical site characterization p. It is not new, and is well proven and well documented. Standard test methods for downhole seismic testing 1. D4428 d4428m14 standard test methods for crosshole seismic testing precision cross hole seismic test seismic crosshole method. Geological survey openfile report 20071124 version 1. The information supplied by these arrays is increasingly becoming the basis for development, verification, and calibration of predictive tools and design.
Us9567845b2 downhole seismic sensor with filler fluid. Standard test methods for crosshole seismic testing. Sed correlation of core and downhole seismic velocities. A seismic source is used to generate a seismic wave train at the ground surface offset horizontally from the top of a cased borehole. The software has an integrated system for the extraction of the first arrivals, both for the p waves and s waves starting from the data in seg2 file format. Application of modern seismic methods for geotechnical. Seismic cross hole method the seismic cross hole method consists of measuring the travel time of seismic waves propagating from a seismic energy source downhole hammer located in one borehole, to detectors downhole geophones placed at the same depth in adjacent boreholes. United states office of research and epa625r92007 environmental protection development september 1993 agency washington dc 20460. Comparison of downhole and laboratory shear wave velocities. Cross hole and down hole tests can be used to measure vs. The crosshole seismic cs system determine shear and compressional wave velocity versus depth profiles. The p and s waves velocities are used in geotechnical foundation analysis, static and dynamic soil analysis, liquefaction assessment and etc. Down hole seismic methods measure travel times to establish seismic velocities that are linked to the stiffness. According to the literature, the seismic piezocone test has proven to be a fast, economical and reliable method to determine go.
The downhole method requires the energy source at surface and the sensors within the hole. Every point on the wave front is a source of a new wave that travels out of it in the form of spherical shells. Downhole seismic velocity logging techniques have been developed and applied in support of highre solution reflection seismic surveys. Downhole survey a sturdy hardwood board is laid beside the wellhead, and a downhole seismic, three component, clamping geophone is lowered into the hole. Traditionally, intrusive seismic methods involving one or more boreholes have been used, with the downhole method most commonly employed over the past. Seismic refraction surveys are conducted to measure the seismic compression velocity pwave and estimate the subsurface stratigraphy. Accordingly, they involve the generation of a short pulse of seismic energy and the permanent recording of the arrival of seismic pulse at distant locations, with time intervals after the. However, the measured seismic velocity is influenced by many factors, such as the presence of. This paper presents a system for performing downhole seismic test together with the piezocone test in order to determine the shear wave velocity vs and for calculating the maximum shear modulus. The seismic method is a powerful geophysical exploration technique that has been in widespread use in ground engineering for more than 40 years and has been increasingly used since 1996 in geotechnical and environmental applications, usually at depths shallower than 40 meters. Masw to map shearwave velocity of soil semantic scholar.
Using these measurements, calculations can then be made of the dynamic soil and rock properties for earthquake design analyses for structures per the usb, liquefaction potential studies. The conventional approach involves lowering a 3component borehole geophone down one hole while lowering a source down an adjacent holes, firing the source at some prescribed depth interval. Once entered the information for the project, the depth reached and the travel times, we can get. This method relies on a surface source to generate p and swaves that travel down the soil or rock column where they are recorded by a sensors locked in a borehole. Astmd7400 standard test methods for downhole seismic. Downhole arrays are deployed worldwide to record seismic ground response in nearsurface strata. Parallel seismic involves hitting any part of the structure that is connected to the pile or foundation or hitting the foundation itself, if accessible and receiving compressional andor shear waves travelling down the foundation by a hydrophone or a geophone receiver. The seismic sensor includes a sensor housing, a bobbin supported in the sensor housing along an axis thereof, at least one coil wound about the bobbin the coil movably supportable within the sensor housing by at least one spring, at least one magnet positionable about the bobbin to generate. Profiles from surface and downhole detectors in the near surface in the southeast niger delta, nigeria abstract seismic refraction survey was conducted in the southeast surfacedetectors, and estimated nearsurface compressionalwave velocities. Cpt is an insitu method that evaluates stiffness by measureing resistance to the penetration of a probe. Crosshole seismic overview a threeaxis geophone is lowered into a speciallyprepared, cased borehole and excited with a hammer source in a similar borehole nearby. Borehole seismic data collected during and after the drilling of exploration and appraisal wells delivers valuable information for reservoir characterization.
Downhole seismic tomography is a downhole geophysical technology. Travel times are collected at regular intervals usually 0. It is assumed that down hole and cross hole tests have similar results. Astm d740014 standard test methods for downhole seismic. These include the cone penetration test cpt lunne, 1997 and down hole seismic dobrin and savit, 1988 methods. The seismic waves can be denoted as p v or p z for a downward propagating compression wave and as s vh or s zx for downward propagating and. Seismic design specification for buildings, structures. Measurement of seismicwave travel time is one of the most common geophysical method. Shear waves are generally measured using a seismic energy source that. Standard test methods for downhole seismic testing1. It is then clamped at intervals, commonly five feet, and at each interval the board is hammered.
Pdf measurement and interpretation of downhole seismic cone. Seismic while drilling swd techniques with downhole measurements, introduced by ifp and its partners in 19902000. The method to do down hole seismic is to install geophone on the bore hole, than making artificial trigger on the surface. Suspension logging offers the only method that gives both p and shwave velocity measurements reliably in a single hole at depths greater than 200 ft. Downhole seismic velocity logging is a well known method of measuring seismic wave velocity profiles, and has been used for more than 50 years. Investigation into the weathering layer using uphole method. This website beta version contains information on geophysical methods, references to geophysical citations, and a glossary of geophysical terms related to environmental applications. In this study, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. The waveform, frequency, and noise characteristics of the shear waves generated by seismic hammers, and measured by the seismic cone are described. Seismic methods can provide valuable information of the subsurface, such as the seismic velocity structure of the geology e. A number in parentheses indicates the year of last reapproval. The method may be used to find the in situ low strain shear modulus for use in theoretical response studies. The downhole seismic method dh measures the time taken for the p and s waves to move between a seismic source located on the surface of the ground, and the receivers, placed inside a borehole. The core and downhole velocities deviate by up to 2 kms.
The method of down hole seismic surveying is described. The impulse or artificial trigger can be rise compression wave and shear wave. Seismic methods can provide detailed information about rock properties and geological structure between boreholes. It is similar in several respects to the crosshole.
The downhole seismic ds investigations are similar to cs investigations, but require only one borehole to provide shear and compressional velocity wave profiles. Disclosed is a seismic source forming part of a drill string which allows geological prospecting while drilling a borehole. For free space, the onedimensional wave equation is derived. This method relies on a surface source to generate p and swaves that travel down the soil or rock column where they are. Historic projects include the seismic retrofit of all of californias toll bridges, yucca mountain project, and others.
The paper concludes with a recommendation for conducting downhole scptu and data interpretation, which are in line with the new iso standard on marine soil investigations. This method was successfully used to a depth of 50 m in a cased borehole and these results are presented. A preferred method intended to obtain data for use on critical. Seismic reflection methods environmental geophysics us epa. Pdf seismic downhole arrays and applications in practice. At each station, a borehole was drilled with casing down to 60m depth, wave velocities. The down hole seismic explosive sources currently in use, as shown diagrammatically in fig.
Analyze the test data following the procedure and obtain the velocity profiles for swave. Basic principles of the seismic method tu delft ocw. It is assumed that downhole and crosshole tests have similar results. There are advantages and disadvantages to either method. Crossholedownhole seismic csds investigations provide information on dynamic soil and rock properties. Measurement of seismic wave travel time is one of the most common geophysical method. The correlation of seismic properties measured on borehole cores with surface seismic data constrains the origin of this reflectivity. Seismic while drilling swd is a well seismic method developed in recent years which is based on reverse vertical seismic logging.
Seismic refraction is the most commonly used geophysical method. The pwave and swave velocities are directly related to the important geotechnical elastic constants of poissons ratio. Borehole seismic imaging reservoir characterization. Standard test methods for downhole seismic testing. The pwave and swave velocities are directly related to the important geotechnical elastic constants of poissons ratio, shear modulus, bulk modulus, and youngs modulus. A preferred method intended to obtain data for use on critical projects where the highest quality data is required is included. Astm d740008 standard test methods for downhole seismic testing. First it is hammered on one of its ends and a record is made. Downhole dh and crosshole sh seismic methods involve measuring the time required for p and s waves to travel from seismic source, located at the ground surface or in drilling, to the.
This isnt my work but is for benefit of my classmates and juniors. A seismic source is used to generate a seismic wave train at. The downhole receivers may be positioned at selected test depths in a borehole or. Application of modern seismic methods for geotechnical site. A seismic sensor for a downhole tool positionable in a wellbore penetrating a subterranean formation. The results of a downhole seismic survey generally include traveltime plots and velocity graphs for both p and shearwaves, as illustrated below. If there is concern about a nearsurface velocity inversion, a downhole survey can shed light on this and help constrain the results of a refraction survey. Instead of a radio signal, a seismic signal is sent out and whatever comes back is recorded. Toksoz earth resources laboratory department ofearth, atmospheric, and planetary sciences massachusetts institute oftechnology cambridge, ma 029 abstract. Structural changes and changes in the stress state of samples usually result.
A seismic signal is produced by hammering a piece of wood placed on ground with a hammer. Soil ground is assumed to be three horizontally stratified layers. Introduction the up hole method of seismic refraction survey is a field seismic technique which uses receivers on the ground surface and an underground source to derive information about the subsurface lithology. Seismic exploration is divided into refraction and reflection surveys, depending on whether the predominant portion of the seismic. The source includes a section of drill pipe having a spiral cam machined into its outer surface and a port for allowing mud to flow from the inside of the drill pipe into the borehole. Pdf measurement and interpretation of downhole seismic. It allows for direct path measurements associated with each set of impacts. Seismic method including single channel seismic and multichannel seismic method is one of the most effective methods for the identification and prediction of submarine gas hydrate. The downhole seismic method involves a test that is a less expensive and.
Combined with surface seismic data, borehole seismic surveys can help calibrate results and improve your predictions, as well as image specific reservoir features around the borehole. In addition, the material damping can be determined from cs tests. The crosshole method was popularized earlier than down hole, and has been an astm standard, so it will often be specified on bid documents. Plastic casings were installed in the hole to prevent the hole from collapsing and caving in. Crosshole and downhole tests can be used to measure vs. Before lowering the hydrophones string, a heavy metal was attached to the end of. From these measurements, parameters, such as poissons ratios and moduli, can be easily determined. However, crosshole geophysical testing may show that the ground has been suitably improved in some cases where cone penetration tests are unable to demonstrate an equivalent level of improvement. Astm d7400 14 standard test methods for downhole seismic. The ds method uses a hammer source at the surface to impact a wood plank and generate shear and compressional waves. Seismic rays are used instead of the wave front to describe the wave propagation. Geophysical method an overview sciencedirect topics.
Ye yincan et al, in marine geohazards in china, 2017. A seismic signal would travel to the seismic sensors. Seismic design specification for buildings, structures, equipment, and systems. Fewer boreholes are needed to achieve a continuous picture of the subsurface thereby reducing overall costs and the risk of missing target features.
Figure 3 summary of downhole seismic test results for dh1. Crossholedownhole seismic csds investigations provide. Seismic while drilling swd, specifically encompasses the seismic techniques operated while the drillstring is lowered in the borehole, during effective drilling, during manoeuvres or while connecting drill pipes. In the earth, seismic waves can propagate as longitudinal p or as shear s waves. This procedure is covered by an astm guideline but has several variants. Owing to the high cost of this test, the cone penetration test method is generally used. Pdf shear wave velocitydepth information is required for predicting the ground motion response to earthquakes in areas where significant. Crosshole or crosswell seismic measures the velocity of seismic waves between boreholes. Seismic methods depend upon velocities of acoustical energy in earth materials.
This paper presents a system for performing down hole seismic test together with the piezocone test in order to determine the shear wave velocity vs and for calculating the maximum shear modulus. Measurement of shear waves s can be invasive borehole seismic surveys and logging or. Various applications of the data will be addressed and acceptable procedures and equipment, such as seismic sources, receivers, and recording systems will be discussed. Crosshole seismic cs and downhole seismic ds tests are performed on soil and rock sites to measure the inplace shear and compression wave velocity profiles of the soil and rock versus depth.
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