Waveform approach velocity spectrum and common velocity stacks cvs stack the records along trial reflection hyperbolas. This website beta version contains information on geophysical methods, references to geophysical citations, and a glossary of geophysical terms related to environmental applications. The charge depth and size at the test shot locations was selected based on the uphole data and the quality of seismic data of the preceding swaths. The seismic design criteria will be met by using the 2019 cbc for seismic design. The first method in this part which is also called the well shooting or downhole or uphole seismic method is commonly used for determining rock structure and characteristics in the immediate vicinity of the hole. Geophysical seismic refraction and uphole survey analysis. Pdf in this paper, an uphole refraction survey was carried out at the location of liso field in niger delta nigeria in order to determineestimate the. Seismic exploration is divided into refraction and reflection surveys, depending on whether the predominant portion of the seismic waves travel is horizontal or vertical. From the analyses, the minimum velocity for uphole diffraction is 2ms1 while the maximum velocity for uphole diffraction is 781ms1. The timeintercept technique of seismic refraction interpretation was employed while the conventional method of well shooting. The present invention relates to applied geophysics method of exploration technology, is a kind ofly utilize more than three mouthfuls or three mouthfuls well head threecomponent seismometers to carry out the method for waterfrac treatment micro seismic monitoring. Seismic exploration is divided into refraction and reflection surveys, depending on whether the predominant portion of. The weathered layer seismic refraction uphole data and that of the surface refraction data gotten from each location were computed and analyzed. Seismic refraction surveys are now routinely used in foundation studies for construction projects and siting studies, fault investigations, dam safety analyses, and tunnel alignment studies.
Seismic rays are used instead of the wave front to describe the wave propagation. Now to display uphole numbers near the uphole markers, select the post map for uphole in the object manager. A kind of method utilizing uphole seismograph to carry out waterfrac treatment micro seismic monitoring. Instructional material complementing fema 451, design examples seismic load analysis 9 17 1a, 1b stiffness soft story irregularity vertical structural irregularities irregularity 1a exists if stiffness of any story is less than 70% of the stiffness of the story above or less than 80% of the average stiffness of the three stories above. Evaluation of shear wave velocity profile using spt based. Investigation into the weathering layer using uphole. A study of uphole to determine the shooting medium for seismic reflection survey at himalayan foot hill area binode chetia frontier basins, ongc, dehradun email. The description of the geometry of refracted waves is more complex than that of reflected ones.
Reflection seismic method university of saskatchewan. Slope of the graph in t2x2 diagram is 1v stacking2. For free space, the onedimensional wave equation is derived. Nearsurface swave velocity from an uphole survey using. Analyze the test data following the procedure and obtain the velocity profiles for swave. This survey represents a step change in seismic data acquisition providing greatly enhanced data quality by full wide azimuth and very dense spatial sampling complemented by good quality uphole and simultaneous 3d vertical seismic profile vsp recording. The first method in this part which is also called the well shooting or downhole or uphole seismic method is commonly used for determining rock structure. Figure 1 is a schematic of a seismic refraction test. The uphole was drilled to 60m depth using the rotary method and flushed continuously for 20 minutes to enhance stability. Now we record not just pwaves but also converted swaves for a wide range of objectives. The use of uphole method in the mapping of the thickness and. Downhole receivers are used to detect the arrival of the seismic wave train. Introduction to seismic method linkedin slideshare. Pdf application of uphole seismic refraction survey for subsurface.
A hole drilled to a depth below the weathered layer contained hydrophones. These surface data show events with characteristics of swave. Surfacerecorded seismic data often comprise the largest database that must be dealt with in reservoir development. Using the uphole time simplification, the delay method equations from figure 3 can be rewrit ten so that the receiver static is simply thesum of shot static at. Analysis of the results shows that the thickness of the low velocity layer in the region varies from 2. Since the 1920s, seismic reflection techniques have been used to. These corrections are based on 1 uphole data direct. Low velocity layer characterization in the niger delta. A kind of method utilizing uphole seismograph to carry out waterfrac treatment microseismic monitoring. This method is called the standard penetration test sptuphole method because it uses the impact. Seisimager downhole manual, 20, windows software for analysis of downhole. The weathered layer seismic refraction uphole data and that of the. Analysis of different interpolation methods for uphole. Investigation into the weathering layer using uphole method.
Description of the system and method figure 6 typical wave profile and the identification of the mini mum point of the s waves rocha, 20. In this paper, an uphole refraction survey was carried out at the location of liso field in niger delta nigeria in order to determineestimate the thickness and velocities of the strata with a view to ascertaining the suitability of these layers for seismic reflection data acquisition and engineering structures. Singh and brijesh kumar geophysical services, ongc, jorhat, india summary depiction of depth through different experiments for placement of charge is a prerequisite for seismic data acquisition. The uphole method of seismic refraction survey is a field seismic technique which uses receivers on the ground surface and an underground source to derive. In the earth, seismic waves can propagate as longitudinal p or as shear s waves. It was used in seismology for determining the mohorovicic discontinuity, and to discover the nuclei of earth. This involves rotating drilling stem by manual labour and pumping water.
The drilling was by manual rotary method using steel pipes. In the geophysics of oil exploration and reservoir studies, the seismic method is the. This article explores uphole data and vs models obtained from a field experiment carried out by ecopetrol sa, at a valley in the andes mountains of colombia. Application of modern seismic methods for geotechnical site. The earliest applications of the method primarily concerned the determination of the depth to bedrock beneath a soil cover. Analysis of different interpolation methods for uphole data. In practice, the measured travel time is influenced by charge size, by filter setting, by instrument sensitivity, and by previous history of the shot hole. The present invention relates to applied geophysics method of exploration technology, is a kind ofly utilize more than three mouthfuls or three mouthfuls well head threecomponent seismometers to carry out the method for waterfrac treatment microseismic monitoring. Introduction the uphole method of seismic refraction survey is a field seismic technique which uses receivers on the ground surface and an underground source to.
A modified form of the uphole method is introduced in order to obtain efficiently the shear wave velocity v s profile of a site. Uphole survey, seismic refraction, pwave velocity, weathering layer, consolidated layer. Modal analysis determination of seismic design forces based upon the theoretical response of a. Application of uphole data from petroleum seismic surveys to. The uphole method is a seismic refraction method which is used to determine the thickness and velocity of the weathered layer and is a very important criterion. In twentyseven 27 locations within niger delta, nigeria, surface refraction and uphole refraction surveys were carried out. Analysis of different interpolation methods for uphole data using surfer software p. Well seismic surveying and acoustic logging edp open. Geophysical seismic refraction and uphole survey analysis of. This method is called the standard penetration test spt uphole method because it uses the impact. Unfortunately insufficient emphasis has been given to ensuring that the uphole and depth information is correct or that they are applicable to the general formulae. These methods determine geological structure and rock velocities by either refracting or reflecting waves off boundaries between rock units with different seismic velocities or impedance.
Downhole seismic refraction survey was therefore conducted at twenty 20 borehole locations within parts of niger delta, nigeria to determine the low velocity layer characteristics of the. Seismic design specification for buildings, structures. The uphole lithology was sampled every 5m or at the change in lithology. Traveltimes from uphole survey operation carried out in 50 locations in the southeast niger delta were picked and analyzed to determine the area weathering structure using the timeintercept method. Introduction the uphole 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. Application of uphole seismic refraction survey for subsurface. A seismic source is used to generate a seismic wave train at the ground surface offset horizontally from the top of a cased borehole. Modal analysis determination of seismic design forces based upon the theoretical response of a structure in its several modes of vibration to excitation.
A study of uphole to determine the shooting medium for. Cn104215934a method for performing hydraulicfracturing. Uphole article about uphole by the free dictionary. Static corrections for seismic reflection surveys michael j. Reflection seismology is similar to sonar and echolocation. Application of uphole seismic refraction survey for. A nearsurface swave velocity model was obtained from an uphole survey using seismic events identified as swaves generated by explosive sources. The uphole method is a seismic refraction method which is used to determine the thickness and velocity of the weathered layer and is a very important criterion used in deciding the charge depths in any seismic reflection survey. Uphole surveys were conducted about 2 km apart along each seismic line, and were used to calculate weathering corrections required to further process in the seismic data.
Seismic energy sources, whether at the earths surface or in shallow boreholes, produce wave types known as. Seismic refraction surveys are also used to estimate rippability appendix c. The corporation is pleased to announce that additional production testing conducted on the exploration well indicates the load water from the initial artificial fracturing operation has been largely recovered. Can shallow refraction survey replace uphole survey. The basic principle of all seismic methods is the controlled generation of elastic waves by a seismic source in order to obtain an image of the subsurface. Up hole survey, seismic refraction, pwave velocity, weathering layer, consolidated layer. Pdf application of uphole seismic refraction survey for. Investigation into the weathering layer using uphole method of. The potential of this method to obtain a nearsurface vs model, and its potential application to a land surface 3c seismic survey are explored. In seismic reflection work, one very important method in eliminating this. However, seismic data have one shortcoming that can limit their usefulnessthe reflection events used to map the seismic sequences and the seismic facies that describe the areal and vertical distributions of reservoir and sealing units are measured as. 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 model was obtained by picking zero offset events analogously to the method used for pwaves. Singh summary an attempt has been made to understand the different interpolation techniques using surfer software.
Each hole was cased with perforated 6 inch pvc pipe. The problems of poor data quality and statics in seismic surveys have been attributed to lack of proper understanding of the low velocity layer characteristics of the area from which such data was acquired. The downhole receivers may be positioned at selected test depths in a borehole or. Basic principles of the seismic method tu delft ocw. 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. Weathered layer delineation in an x field in the niger. The uphole travel time for the seismic impulse from a dynamite explosion is usually taken to depend only on charge depth and formation velocity. Basic principles of the seismic method in this chapter we introduce the basic notion of seismic waves. Successive sources at varying depths in a borehole in order to determine the velocities of the nearsurface formations, the weathering thickness, and sometimes the variations of record quality with source depth. Microzonation seismic zoning, generally by use of maps, for land areas smaller than regions shown in typical seismic code maps, but larger than individual building sites. The average uphole velocity across the 27 sites is 504. Estimation of longwavelength nearsurface velocity and low. Standard test methods for downhole seismic testing1.
The objective, principle, method and procedure of the downhole seismic velocity logging test. Measurement of seismicwave travel time is one of the most common geophysical method. In the study area, the sparsely spaced and shallow uphole control points could not be used to generate a reliable 3d average velocity model because the base of weathering is well below the maximum uphole penetration depth and srd. For groundmounted experimental equipment, use the following strength design load combinations of asce 716 section 2. Seismic refraction method the first seismic method utilized in the field of exploration. Deep upholes to the depth of datum are necessary to tie ssr data with litho sections of upholes. Approximately 0 uphole surveys were completed in the concession area between march 1981 and june 1983. The standard method of calculating these is to use uphole times and shot depths. Seismic waves are pulses of strain energy that propagate in solids and fluids. Seismic survey is the geophysical method, which is most closely related to rock and soil mass properties, since seismic wave velocity varies with the main mechanical properties, such as poissons ratios and others modules.
Every point on the wave front is a source of a new wave that travels out of it in the form of spherical shells. The role of statics application in the imaging of subsurface. Comparison of the characteristics of low velocity layer lvl in the. The uphole method is a field seismic test which uses receivers on the ground surface and an underground source. We are able to sometimes better image the subsalt and subbasalt targets with the 4c seismic method.
It is achieved by shooting a series of shots in a hole and recording the results in time. Soil ground is assumed to be three horizontally stratified layers. Uphole survey the uphole survey provides a direct measurement of the seismic energy travel time in the low velocity layers and in the layer immediately below. Uphole and downhole seismic refraction studies are the. Checkshots and vertical seismic profiles aapg wiki. Using the multicomponent seismic method, commonly known as the 4c seismic method, we are now able to see through gas plumes caused by the reservoir below.
The wave phenomena occurring at a boundary between two layers are discussed, such as snells. The grain size analysis was accomplished using the sieve method for the sands. The uphole data were also compared to data from a 2d seismic line acquired at the same place. Reflection and refraction are the most commonly used seismic techniques. Ofomola mo 2011 uphole seismic refraction survey for low velocity layer determination.