Figure 6 example of a borehole gravity tool that succeeded where conventional. Seismic refraction tomography srt olson engineering. Contact olson instruments when adding on to an existing system, or purchasing multiple systems as some of. Krahenbuhl, cericia martinez, yaoguo li, and guy flanagan. Applications of tomography in oilgas industry part 1. There are several types of tomography used by geophysicists, including transmission tomography which uses measurements between boreholes, surfacetosurface, or between a borehole and the surface, reflection or seismic tomography based on standard reflection seismology, and diffraction tomography using fermats principle for computations. For swave tomography a newly developed digital multistation acquisition borehole system was used to receive swave signals in an efficient way.
The cross borehole tomography data can map conductive zones between boreholes up to 180 m apart. Borehole seismic methods largely fall into two categories, namely, crosshole seismics and seismic tomography. Important differences exist, however, between cross borehole seismic velocity images and sonic logs. Using stochastic borehole seismic velocity tomography and. Seismic tomography, crosshole, downhole geotomographie gmbh. Introduction to the traveltime tomography and prestack migration for boreholedata within reflexw in the following the use of the traveltime tomography and the prestackmigration for different types of borehole data is described. Introduction to the traveltime inversion problem 0. Combining borehole and surface seismic data for velocity. Divingwave tomography uses first arrivals picked from surface seismic data to compute a nearsurface earth model by minimizing the difference between calculated and observed traveltimes. 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. This paper summarizes the develop ment of a prototype tool and results from recent field tests. Seismic tomography seismic tomography uses an array of borehole and possibly surface geophones or hydrophones to characterize materials outside a borehole. A hammer blow or explosive charge the shot generates a shock wave that travels through the ground which is refracted along material boundaries, and is then received at the surface by sensors geophones.
Ultraseismic, seismic wave reflection, transient force vibration, parallel seismic, induction field, borehole logging, dynamic foundation response, borehole radar, borehole seismic integrity testing of foundations and structures crosshole sonic logging, crosshole sonic logging tomography, gammagamma density. Borehole geophysics is an aspect of geoscience that deals with the vertical analysis of the conditions of the subsurface and its fluid content. Surface and borehole seismic characterization of the boise. Borehole seismic tomography borehole seismic tomography enables the definition of the quality of ground through an analysis of variations in the velocity of seismic shock waves. This chapter illustrates the use of seismic tomography modalities in hydrocarbon exploration, reservoir monitoring and production monitoring.
Seismic methods can provide detailed information about rock properties and geological structure between boreholes. Seismic refraction tomography srt the seismic refraction method uses p and swave energy to map vertical and lateral subsurface changes. Borehole seismic imaging reservoir characterization. Seismic data measured with receivers, sources or both in a well, such as a checkshot survey, vertical seismic profile vsp, crosswell seismic data or singlewell imaging. Geophysical methods provide accurate data about the structure of the subsurface valuable information in the field of engineering. To save the boreholes from damage by explosives other sources were required. Each shot is recorded by all receivers in the borehole and on the surface.
The traveltime tomography allows to build a velocity model from the first arrival traveltimes. The inversion method we use is flexible such that, depending upon calculated ray coverage, we can reduce or add complexity to the velocity model to ensure that inversion is both stable and accurate. Single borehole vrp data can detect conductive zones within a 30 m range around the borehole and it also provides an independent estimate of bulk 4 100 m resistivity for calibration interpretation of other em datasets. An accelerometer is also included to trigger data collection for downhole seismic testing. The csds2 model is the base model for crosshole or downhole seismic testing. Jim berrymans lecture notes on crosswell seismic tomography. Highresolution seismic tomography of long beach, ca using. Introduction to the traveltime tomography and prestack. Borehole logging and crosshole seismic tomography investigation of unconsolidated soil materials in sikeston, mo, helped in defining the engineering properties of the investigated earth material interposed between two boreholes for a depth of 39 m below the surface. Willis earthresourceslaboratory department of earthandplanetarysciences massachusetts institute oftechnology cambridge. Development of the borehole 2d seismic tomography software. Moret, the pennsylvania state university, university park, pa michael d.
Pdf using stochastic borehole seismic velocity tomography. Borehole seismic, llc bringing energy production home. Geophysical techniques surface and borehole geophysics. Borehole seismic tomography developed from a series of lectures by james g.
From these measurements, parameters, such as poissons ratios and moduli, can be easily determined. Detailed seismic tomography in radial boreholes, 1996 2 2. The fact that prolonged subvertical anomalies may disappear in the final velocity model is well known. Detection of local inhomogeneities by means of cross. Crosshole or crosswell seismic measures the velocity of seismic waves between boreholes. Toksoz earth resources laboratory department ofearth, atmospheric, and planetary sciences massachusetts institute oftechnology cambridge, ma 029 abstract. This system includes two triaxial geophones and all necessary accessories for crosshole seismic testing when used with a downhole source. A borehole seismic tomography experiment was successfully conducted using pwaves and swaves. One of the main results of borehole geophysical experiment is the time to depth relation curve.
It should also be noted that tube wave energy can affect the optimum reflection win dow. Fewer boreholes are needed to achieve a continuous picture of the subsurface thereby reducing overall costs and the risk of missing target features. It is the technique employed in order to have a firsthand well evaluation in the exploration for hydrocarbons. Semore offers a fully independent microseismic processing and survey design service based on our proprietary software, divine. A borehole source generating horizontally polarized swave was used. This chapter illustrates the use of seismic tomography modalities in hydrocarbon. The information obtained from cross borehole tomography, when properly interpreted in the context of all available information, can often be invaluable for preparing accurate geological cross sections for reservoir development and planning. Rayfract seismic refraction and borehole tomography software provides subsurface seismic velocity models for geotechnical engineering and exploration.
We use a machine learningbased tomography method to obtain highresolution subsurface geophysical structure in long beach, ca, from seismic noise recorded on a. The connection with the radon transform and the methods of ordinary xray tomography suggests the term seismic reflection tomography srt. The sparker produces repeatable shots and allows a firing rate of the same order as typical listening times in borehole seismic applications. We picked first arrival times and then calculated the velocity model by dividing the distance between the sourcereceiver pairs by the picked arrival time. Surface seismic tomography suffers from the wellknown velocitydepth ambiguity problem.
A lowfrequency downhole sparker for borehole seismic. Multiple seismic source locations, both within the boreholes and along the ground surface, create intersecting seismic raypaths. Crosshole seismic tomography and borehole logging for. The seismic tomography is used to obtain image from structures belowunder the earths surface. So, including borehole data as constraints is essential for the important task of producing seismic images that tie the well. In this software, we used travel time of seismic waves from source to receiver by using pseudo bending ray tracing method as input for tomography inversion. The integration between abaqus and matlab offers many opportunities for solving inverse problems in general. Diving waves sample the near surface with more redundancy and with a greater angular range than reflected waves, enabling you to converge on a more robust. An area of ground is imaged, which allows the reconstruction of a model of this internal area. Based on numerical simulation, herein we comprehensively applied both crossborehole electrical resistivity tomography ert and crossborehole seismic computed tomography ct to urban underground karst surveys of the hangzhoufuyang intercity railway. The crossborehole tomography data can map conductive zones between boreholes up to 180 m apart. Detection of local inhomogeneities by means of crossborehole.
Quintero abstract many seismological studies depend on the accuracy of timing of seismological data. Introduction to the traveltime tomography and prestack migration for borehole data within reflexw in the following the use of the traveltime tomography and the prestackmigration for different types of borehole data is described. Detection of systematic errors in traveltime data using a. The crosshole seismic cs system and method determine shear and compressional wave velocity versus depth profiles. Ultraseismic, seismic wave reflection, transient force vibration, parallel seismic, induction field, borehole logging, dynamic foundation response, borehole radar, borehole seismic integrity testing of foundations and structures crosshole sonic logging, crosshole. Because of the unique distant resolution capabilities of borehole gravity, these data provide a useful integrating tool at the seismic wavelet scale. Collect surrogate data, such as tomography data and hydraulic data and combine geostatistically soft kriging or anealing process, daylewis.
The information obtained from crossborehole tomography, when properly interpreted in the context of all available information, can often be invaluable for preparing accurate geological cross sections for reservoir development and planning. Pdf borehole seismic tomography inversion using artificial. By directly measuring the acoustic velocity of each formation encountered in a well, the well logs and borehole seismic data can be correlated to surface seismic data more easily. Swave borehole tomography a tool for geotechnica l site. Solution borehole seismic reprocessing services use fewer assumptions, so our solution suffers from fewer artifacts or biasedtrend issues.
In the mining industry, classic methods to build a grade model for ore deposits are based on kriging or cokriging of grades for targeted minerals measured in drill core in fertile geological units. But distortions are also inherent to images of local inhomogeneities. Scroll down to see a list of key features and models available for the crosshole seismicdownhole seismic and psv source systems save money. Scroll down to see a list of key features and models available for the crosshole seismic downhole seismic and psv source systems save money. We gather nondestructive measurement data by means of airborne geophysics, along the earths surface as well as in or from tunnels and boreholes. Knoll, cgiss, boise state university, boise, id abstract detailed information about the spatial distribution of subsurface properties is important in many fields. Application of crossborehole integrated geophysical. Applications structural analysis, control of foundations. Seismic tomography has been developed to solve geophysical and geological problems. Our specialists use seismic borehole tomography to explore underground geological structures and identify features of the subsoil, such as layer boundaries, cavities, weak zones, karst caves, loose zones and strongly disturbed earth. Surface to borehole borehole to surface measurements resistivity, em, and seismic tube waves surface or borehole nmr may be useful identify correlations with surrogate data. We have over 25 years of continuous microseismic processing, development and application experience covering onsite realtime data acquisition and processing, near real time processing, off site and reprocessing of legacy data.
The inversion of seismic traveltime data for radially varying media was initially investigated by herglotz, wiechert, and bateman the hwb method in the early part of the 20th century 1. Manufacturer of seismic borehole equipment for tomography, crosshole and downhole applications. Applications of tomography in the upstream oilgas industry are widespread, covering from kilometre reservoirscale, submetre borehole scale, to submm rockcore pore scale. Borehole seismic data collected during and after the drilling of exploration and appraisal wells delivers valuable information for reservoir characterization. Using stochastic borehole seismic velocity tomography and bayesian simulation to estimate ni, cu and co grades. The principal wave types are the refracted p and s waves and the two. This numerical study is devoted to distortions of local anomalies which are revealed by 2d and 3d crossborehole seismic tomography based on first arrival travel times. A site investigation through integration of reservoir properties, seismic imaging, and borehole and surface gravity data richard a. A borehole source generating horizontally polarized s. The energy of the highfrequency sparker proved to be insufficient, so a bolttype airgun was used as impulse source. Detection of systematic errors in traveltime data using a minimum 1d model. Between boreholes, from the surface and in combination with borehole scans. Contact olson instruments when adding on to an existing system, or purchasing multiple systems as some of the components are common to other test methods. Oct 18, 2019 we use a machine learningbased tomography method to obtain highresolution subsurface geophysical structure in long beach, ca, from seismic noise recorded on a largen array with 5204.
The value of borehole tosurface information in nearsurface crosswell seismic tomography geoff j. Important differences exist, however, between crossborehole seismic velocity images and sonic logs. We can also set up a model parameterization, initial velocity model, ray tracing processes, conduct borehole seismic tomography inversion, and finally visualize the inversion results. Geotomographie, founded in 1999 in germany, provides complete solutions for borehole and nearsurface seismic surveys to geophysical, engineering and mining companies.
Combining borehole transmissions and reflections in isotropic slope tomography, to obtain a single velocity model, is exemplified. But, if a seismic horizon is near the base of the borehole, we must change the experiment to image the reflections from the top of the seismic unit. 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 the gulf of mexico example shown in figure 5, amoco used its borehole gravity log to help interpret a detailed cross borehole seismic tomography image. Crossholedownhole seismic csds investigations provide information on dynamic soil and rock properties. In seismic tomography, traveltime residuals defined as differences.
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