Sonic log to velocity conversion. 5 Synthetic Seismogram.

Sonic log to velocity conversion Post sonic log prediction, lithology determination is performed with the help of an unsupervised ML algorithm, k-means clustering. It refers to the speed at which sound waves travel through a medium, such as air, water, or solids. Calculate V. From a theoretical point of view, Finally, the interval velocity obtained from the slowness was converted to RMS using the seismic processing software ProMax/SeisSpace applying the Dix Equation Introduction Sonic log is a measurement of mechanical wave slowness (the inverse of the velocity) throughout the formation, produced by a source located inside a tool immersed in a fluid filled borehole. The input velocity can either be a compressional or shear velocity and will be automatically converted to the respective compressional or shear slowness. The difference between the two defines the (D) velocity-deviation log, which is plotted with The purpose of this course is to introduce the student to velocity modeling, velocity handling and domain conversion functionality in Petrel. Stratigraphic control is available for 21 of the 22 11. The sonic velocity is a crucial factor in designing acoustic equipment, studying atmospheric phenomena, and improving aerospace technologies, among other applications. It describes: 1) Computing interval velocities directly from sonic logs that have integration ticks by counting ticks and dividing integrated time by interval The most common application is the estimation of porosity from values of compressional seismic velocity (Vp). View Calibrate All Sonic Velocity Logs to VSP Interval Velocity Curves. Stacking velocity is related to the zero offset time domain, i. N. grain to grain packing. The most common form assumes velocity varies linearly* with depth and hence are defined in the form y=mx+c: Vinst = Depth Conversion Process Robert L Pickering . Analytical velocity functions allow us to build our velocity model based on the velocity trend we see on log data. This objective of this paper is to illustrate the value of extracting and applying velocity information from sonic digital data. The wells were chosen because they Abstract Well ties to seismic data establish the fundamental link between geology as we measure it in a well bore and the seismic expression of geology that we work with as interpreters. Velocity log analysis . This tutorial presents an example of tying a well to time-processed seismic data using a blocked sonic log for a case in which neither a vertical seismic profile, a synthetic seismogram, nor a check Pseudo Density Log builds a bulk density log from an input sonic log sampled in depth. Converting the sonic log to porosity by applying the Wyllie time-average equation (W yllie et al. Like this? Please share. Calculate velocity (replacement) and 2WT from the seismic reference data (SRD) to the shallowest sonic log recording. (1956) suggested a relationship Sonic logs, check shots and VSPs; Conversion of velocity types (e. This algorithm helps us to define an optimum number of clusters (Mohamed et al It depends on where in the subsurface pressure system. Lindseth, (1982). Modes are configured to meet the logging conditions presented by different borehole environments. From a theoretical standpoint, the continuous sonic should be the best, and most, complete form of velocity information possible to obtain at a given location. 28084; The converted shear and the pseudo-Rayleigh arrive at the monopole detector with nearly the same velocity and cannot usually be separated. o Sonic log o Density log o Neutron log Sonic logging is recording of sound wave velocity in rocks. , 1985, Study of sonic velocity in Upper Assam Valley This document discusses techniques for deriving velocity models from sonic logs. , 2018) as a significant step in seismic data interpretation and inversion (Margrave, 2013). 1-1a. If there is pore space in the rock, and it is fluid-filled, the acoustic energy will take longer to get from the transmitter to the receiver (i. LookBack Exploration Ltd has developed a processing routine can provide a reliable source of stable, geologically sensitive velocity data from sonic log data. This objective of this paper is to illustrate the value of extracting and applying velocity information from sonic digital data. K. 5, Fig. Here, velocities were measured between the 1000- to So you could not use the velocity map with the K measured from sonic logs to depth convert the interval base. Thus travel time of a wave is the distance that the wave travels times the slowness of the medium ( in seismology, it refers to different layers of Earth exhibiting different Sonic Velocity refers to the speed at which a fluid, typically a gas, travels when it reaches the speed of sound in that particular medium. Reflectivity/Synthetic Logs Linear regression of the sonic velocity logs 12 Table 4. Invasion corrected logs in V p, V s, Rho and AI track are in red. Also called the sonic porosity, travel-time log, and continuous-velocity log, this method uses calculated Vp values to estimate porosity by using the Wylie, Rymer-Hunt, or other equation (Paillet and Cheng, 1991). However, there are significant needs to gain the resolution higher than the Discrepancies between sonic log and seismic velocities Figure 4 The drift demonstrating the existence of discrepancies between sonic log and seismic velocity tween sonic log and seismic and when adjustment were carried out in order to match both curves were, the effect on sonic log is quite considerable, as can be seen in Figure 7b. In Academia it is not common to have checkshot or VSP data for a well. , 2020). This is shown by the following equation: log(ρ)=b*log(V)+log(a)(4) where log(a) is converted back to a. , Raju, P. Sonic (1/velocity) and resistivity (1/conductivity) are subjected to the water saturation vs. The input units of either m/s As observed in these seismic sections, Leon formation presents orange (warm) colours: low velocities; that contrast with the greenish tonalities, higher velocities, in the Guayabo formation above. Multi-well log overlay display 6. 90% and The difference between the real sonic log and the synthetic sonic log can then be plotted as a velocity-deviation log. B. It is useful in the following ways: 1. We can model the velocity over each interval with a straight line. But VSP and sonic log velocities (or traveltimes) are often found to disagree. The first function drift_corr calibrates the sonic log by estimating the difference in velocity Velocity models can be build based solely on or from a combination of checkshots, VSPs, sonic logs or seismic stacking velocities. 49-57. established. , 1990), we perform numerical simulations to demonstrate that the attenuation corrected for geometrical spreading and the phase velocity computed from sonic logs are similar to those obtained for a plane-wave propagating through VSP depth converted to log depth as mentioned earlier. Generating Vs from Vp sonic logs David G. In this case there are two alternate methods that can calibrate the sonic log to the seismic data. If the alternative TWT conversion method was used, then the absolute time at the Given that equation 13 was derived to model the effect of a fracture on the propagation of plane seismic waves (Pyrak-Nolte et al. Travel times are converted to time-depth pairs by referencing them to a single, manually entered, time-depth pair from within the log interval. 4. 4, Fig. A sonic log quantifies the reverse of the instantaneous wave velocity of the rocks in the vicinity of the borehole. Understanding sonic velocity is critical in various fields, including aerospace engineering, acoustics, and fluid dynamics, as it determines the maximum achievable velocity for efficient flow and performance considerations and is represented as C = We would like to show you a description here but the site won’t allow us. Link. unmigrated time. Loading checkshots 2. Sonic travel time ( 4t) is inversely proportional to the speed of sound (v) Seismic to well tie, synthetic seismogram and depth conversion. A magnetostrictive transducer, Studying the correlation of rock properties with P-wave velocity index in dry and saturated conditions. Discover a universal assistant for all of your unit conversion needs - download the free demo version right away! (A) The sonic log provides the true downhole velocity distribution. If we use imperial units, then use the following equation to calculate sonic velocity: V s (sonic velocity) = 223 (k T/M) 0. Velocity model can be obtained from sonic log, which is used to estimates the velocity value of the subsurface from signals that propagate in the vertical direction and at a frequency up to 20,000Hz (Al-Chalabi, 1979). The recorded sonic See more The sonic or acoustic log measures the travel time of an elastic wave through the formation. By writing equation (2) in a log-log sense, a linear equation is obtained where log(a) is the intercept and b is the slope of the best-fit line. 10). 1. Potter and V P , and S-wave, V S , velocity logs to predict density, ρ, values How to convert depht in (double-time Sonic logging is a well logging tool that provides a formation’s interval transit time, designated as , which is a measure of a how fast elastic seismic compressional and shear waves travel through the formations. 2 Velocity to Sonic. These velocity anomalies must be measured and dealt with accurately when mapping the velocity fields that are so critical to an effective surface seismic Using this velocity to convert seismic reflection data from time domain to depth domain, it must match the well data/marker. However, there are significant needs to gain the resolution higher than the Density predictions using V P and V S sonic logs. Shear velocity at sonic log An alternative to improve the final velocity model is to use sonic well logs to get the velocity. Stewart INTRODUCTION The correct identification of primary events on the converted S-wave section in the absence of a VSP or S-wave sonic log may be difficult (Corbin et a1. The P-sonic model was then formed by blocking 1:hestretched P-sonic model (Figure 4c), and both logs were Use this velocity converter to convert instantly between centimeters per second, feet per hour, kilometers per hour, knots, meters per second, miles per hour and other metric and imperial velocity and speed units. Reconciling Sonic Logs with Check-Shot Surveys; Stretching Synthetic added to the sonic log resulting in the calibrated sonic log output. Well top adjustment 7. VelPAK (Kingdom) and Velit (Petrel) will assist you in leveraging your Sonic Log Data to find an Checkshot and VSP surveys give direct measures of both average and interval velocity by recording the travel times and depths from surface to a series of geophone locations Consider a sonic interval velocity log exhibiting 4 velocity breaks. A suite of well logs that included gamma ray (GR), sonic velocity (Vp), bulk density (Rho), neutron porosity (NPHI), density porosity (DPHI) and caliper logs were sourced from 13 wells. R. Optimise well section 3. 3, Fig. seismic velocity calibration, time to depth conversion and True velocity is best obtained from vertical seismic profiles, check shot surveys, or calibrated sonic logs. Well to seismic tie using corrected sonic log 3. • ‘Velocity logs’ gives synthetic logs derived from the velocity model • QC the velocity model by overlying output logs on the input data • The TDR data (rather than raw Vi logs) should be The Generate Checkshots tool can be used to generate time-depth pairs from a sonic log. Limited check shot which may be totally missed by the sonic log. The most common form assumes velocity varies linearly* with depth and hence are defined in the form y=mx+c: Vinst = 9. ,1983). Where: V s = sonic velocity (ft/s) k = ratio of specific heats in the gas (C p /C v) T = absolute temperature Sonic log (DT) correction with check-shot 2. The sonic log data were also used to calculate a compressional wave (V p ) velocity log by taking the reciprocal of the interval transit time log and converting from feet to meters, and to define About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright Relying solely on sonic logs to convert surface seismic travel time to depth may lead to errors in interval velocity. Create a zone log 5. Pseudo Sonic Log Pseudo Sonic Log builds a sonic log using deep resistivity and a gamma ray, deep resistivity, or shallow resistivity logs sampled in depth. Abstract . 2003. Well logs, such as sonic, are used to transfer the wells to the time domain. Empirical relationships between seismic velocity V in ft/s, geologic age T, true formation resistivity ρ in ohm feet, and depth of burial z in feet: = (), = z is sometimes taken to be the maximum to be evaluated empirically from sonic Slowness (s) is a quantity introduced in Seismology which is the reciprocal of velocity. Depending on the information available, the method Furthermore Smith (2007) employed cross–plot methods using two resistivity logs comprising, spherically focused log (SFL) and deep penetrating induction (ILD) with sonic log (DT), provided a method to estimate non recorded sonic log. Interval velocities are calculated from the sonic log and integrated to calculate travel time. Iverson et al. Bed thickness, hole size, caves, alteration of the formation adjacent to the bore, spacing of the This arrangement is suitable for detecting azimuthal velocity variations in a borehole. This process must come first in a flow if any process uses a sonic log. QC checkshot interval velocity points . Checkshot calibration of sonic logs; Discussion of available velocity functions as well as different velocity modeling approaches; Velocity modeling using well data The synthetic CCP gather and the P-sonic log were then correlated to each other using STRATA (Figure 4b). Journal of Applied Geophysics, Volume 169, 2019, pp. The recorded sonic log trace is a permanent record of a measurement recorded by a Raw un corrected logs (Un-corr) of sonic velocity V p, shear velocity V s and density Rho along with computed acoustic impedance AI (V p * Rho) are in black. Depthing can be done via a wide range of existing methods, too many to cover in any This chapter describes the methodology of the speed of sound also known as sonic log. The Acoustic-velocity logs, also called sonic logs or transit-time logs, are a record of the travel time of an acoustic wave from one or more transmitters to receivers in the probe. A magnetostrictive transducer, excited from the surface by a signal, It is related to the velocity in ft/s by eq. This information can also be used to derive the velocity of elastic waves through the formation. Compressional-wave measurements of Olympic Peninsula mafic Only a few of the sonic logs were made with older, short tools, with short spans between the source and receivers. , 1956) is a The result is a wide range of sonic velocity in carbonates, in which compressional-wave velocity ( V P ) ranges from 1700 to 6600 m/s and shear-wave velocity ( V S ) from 600 to 3500 m/s. A sonic log is the best as it is normally sampled at 0. The units of Δt are micro-seconds/ft (μsec/ft) or millionths of a second per VELMA = sonic velocity log reading in 100% matrix (ft/sec or m/sec) VELW = sonic velocity log reading in 100% water (ft/sec or m/sec) Convert travel time to velocity 18: Vp = 10^6 / DTC Sonic Velocities & Depth Conversion Robert Pickering LookBack Exploration Ltd Summary The current method(s) of converting seismic time data to depth are methods created to work-around the Sonic log velocity detail, when collated, processed and applied, is a key critical factor in the Sonic log provides continuous records of different VSP depth converted to log depth as L. Furthermore, sonic logs and resistivity logs, can be applied for source rock assessments of their organic matter contents (Aziz et al. 1 The principal uses of the sonic log (conventional, compressional wave tools and convert pressure waves into electromagnetic signals which can be amplified Indeed acoustic logging in a broad frequency band (1 kHz up to 30 kHz) may provide to estimate the compressional (P-wave), shear (S-wave), Stoneley wave velocity and amplitude. , Singh A. Bhattacharya1 1 Well Logging Services, ONGC, Nazira, Assam 2 Sub Surface Team, Assam Asset, ONGC, Nazira, Assam 3 A & AA Basin, Forward Base, ONGC, Nazira, Assam 5th Conference & Exposition on Petroleum Geophysics, Hyderabad-2004, tween the real and the inverted sonic log, the inversion must be suppled withan estimateof the velocity-depth trend. from sonic log 2. . 6. The sonic log is commonly used to calculate the porosity of formations, however the values from the FDC and CNL logs are superior. To convert ps/ft to ps/m, multiply by 3. Maurya3 & A. Refer appendix for lithology symbols used. 19. 5 Synthetic Seismogram. Such data is applied in the · Sonic Logs – a sonic log is a device which is lowered down a borehole which measures the instantaneous velocity by sending a soundwave into the formation and picking up the refracted Checkshots are generated spaced at regular MD intervals based on sonic log data from the well. 8. RMS to Interval) Import and conversion of velocity text files; Creating Petrel seismic velocity cubes from text files; Module 4: Functional Representation of Sonic logging has been widely used for many years to acquire physical properties of hydrocarbon reservoirs. Schieck and Robert R. Another importance of the sonic logs is related to determining the well-to-seismic ties (Bader et al. e. 5 Acoustic-velocity logs were originally developed for calibrating surface the shear head-wave generated within the formation is converted into a compressional wave and propagated back across the borehole fluid to the R. As frame, and transmission losses due to energy conversion to reflected and transmitted waves at the fracture interfaces. The corrected sonic log is converted to interval velocity. To emphasize the porosity sensitivity of the sonic log, comparison with the neutron and density logs over the same intervals is provided. The initial time-depth relationship used in creating the synthetic seismic trace often is created using the sonic-logging velocity. , and Lowrey, P. The bottom zone is from the carbonate section, and the upper from the shaly sand section. In this way, as this author, calibration of the sonic log includes an analysis of the data to determine the cause of the differences (drift) between the sonic and the check-shots. N. 91 - THE GEOLOGICAL INTERPRETATION OF WELL LOGS - Table 8. Depth conversion using velocity grid 6. 154 Calibration of Sonic Logs for Seismic Applications in Upper Assam Lalaji Yadav 1, Dilip Ghosh2, S. In seismic methods, pore pressure is estimated by converting seismic velocity into pore pressure and calibrating it with pressure results during the well-testing program. The discrepancy between the laboratory velocity measurements and sonic log measurements at Site 1001 is problematic. The conventional sonic log presentations for portions of the simulated reservoir are shown in Fig. (2008) uses velocity field representation and conversion of time image to true geological Vertical seismic profiling (VSP) techniques provide a method to measure accurately the seismic velocity and lithologic structure near the borehole. Other studies used porosity to compute the unknown sonic logs. to flatten events, on unmigrated time gathers and is applied prior to creating an unmigrated stack in zero-offset time. The (B) neutron-porosity log is converted into a (C) synthetic velocity log. This is a smooth velocity field used for normal move out (NMO) correction, i. The sonic log is a plot of interval velocity as a function of depth based on downhole measurement using logging tools. Preferably, the TWT conversion should be done using VSP time-depth. The dipole sonic imager (DSI) is a multiconfigurable tool that can emulate a BHC sonic, a standard monopole array tool, or an array dipole tool. Converting the wells to the time domain is also the time when the geophysicist must decide which seismic event can be associated with which well top. LookBack Exploration Ltd . Add zone log to checkshot The purpose of the sonic log is to measure formation velocity, but various geometrical factors can cause apparent velocity readings substantially different from the true velocity at the depth of measurement. , 1993). i. g. 5. Geologically, this capacity varies with many things including lithology and rock textures, most notably decreasing with an increasing effective porosity and increasing with an The sonic log provides a formation's interval transit time, designated At (delta-t, (1 X 106) / At = sonic velocity, ft/sec. Shear wave transit times can be inferred by making lithologic assumptions based on Vp/Vs ratios thus Acoustic logging tools can assist in evaluating porosity because the compressional velocity of sound in fluid is less than the velocity in rock. We took the sonic log mean as a baseline, and that is because sonic on average increases with depth due to compaction. Converts a velocity curve to a slowness curve. A systematic sonic logging survey was performed along a tunnel during the excavation in horizontal boreholes in Quartzite and Gypsum formations. I used both L1 as well as L2 norm of the sample 9. Create a zone log filter . The analysis of a VSP survey can also provide insight into seismic‐wave propagation especially when related to sonic measurements. The wave velocity in a – Sonic log – Density log – Neutron log • None of these logs measure porosity directly • The density and neutron logs are nuclear foot of formation and is the reciprocal of the velocity • Interval transit time is both dependent on lithology and porosity • Sonic log is usually displayed in track 2 or 3 • Units: It also plots the normalized logs of velocity on the left and density on the right. Linear regression of the density logs 14 Table 5. This velocity inversion also is noted in both the sonic and density logs and the time – depth relations (see A in Fig. 3. Performing blind Sonic velocity, density, and resistivity log data from 60 wells on the Norwegian Shelf and the linear velocity parameters for each layer constitute the input for velocity-anomaly depth conversion. Checkshots are generated spaced at regular MD intervals based on sonic log data from the LookBack Exploration Ltd has developed a processing routine can provide a reliable source of stable, geologically sensitive velocity data from sonic log data. In this work, we characterize the mechanical properties of individual fractures from P wave velocity changes and transmission losses inferred from static full-waveform sonic log data. A sonic log segment is shown in Figure 2. Median filter a log 4. Download Velocity Unit Converter our powerful software utility that helps you make easy conversion between more than 2,100 various units of measure in more than 70 categories. The sonic log; The density log; The neutron log; is the reciprocal of the sonic velocity through the formation. Although sonic logging provides useful information in the subsurface, the resolution of existing methods is restricted to 6 inch defined by neighboring receiver distance of logging tool. In this way, Wyllie et al. 23 Not exam Queertin-Secondary Porosity 24 The unconventional depth conversion method, shown in Figure 3, involves velocity data extracted from processed, or raw, sonic log digital data or velocities extracted from check- shot surveys, the integration of time domain data into the depth domain and the the synthetic sonic log can then be plotted as a velocity-deviation log. Mohammad Rezaei, , Iraj Najmoddini. Convert the data to TWT as described above. Acoustic A Sonic logging has been widely used for many years to acquire physical properties of hydrocarbon reservoirs. Colin C. Since seismic velocity analyses have large lateral variation, Yes. , low velocity indicates high porosity). An understanding of these factors enables one to derive greater value from the log. Recent field evidence of The correlation between pseudo-impedance Time-Depth conversion with TD table (red line) and pseudo-impedance Time-Depth conversion using the three velocity model scenarios (blue line) present Evidently, the sonic log-derived porosities provide better estimates of porosities relative to the density log-derived porosities as it has a lower coefficient of variation (13. Depending on the cause of the drift, different methods of correction are used. Create a Zmid attribute 2. Velocity changes on the P-sonic were correlated to the corresponding events on the S-wave seismJ:c data by stretching the P-sonic log. The successive values obtained are then as compared to interval velocity values derived from sonic log. , 1989; Urmos et al. This chapter describes the methodology of the speed of sound also known as sonic log. Previous studies have shown that shipboard laboratory velocity measurements are often lower than sonic log measurements because of removal of overburden pressure (Hamilton, 1979; Fulthorpe et al. and Bansal C. Average velocities would have to be converted to interval velocities using Dix formula. 14-5. Understanding sonic velocity is essential in various scientific and engineering fields. Here I use a 33-point Savitzky-Golay filter with a sixth-degree polynomial to smooth the velocity log and show that with this trend the velocity log is reasonably well recovered. Checkshot analysis . kuywp ygkw ryavb lvtow pmzvnq eykzvq avnav fsbhqq gxjesq pegp