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#### Refraction statics corrections

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Proceedings Papers

Peter Bergmann, Stefan Lüth, Alexandra Ivanova, Artem Kashubin, Monika Ivandic, Christopher Juhlin, Emil Lundberg, Fengjiao Zhang

Publisher: Society of Exploration Geophysicists

Paper presented at the 2012 SEG Annual Meeting, November 4–9, 2012

Paper Number: SEG-2012-0686

...Cross-correlation time-lapse

**static****corrections**versus**refraction****static****corrections**on 4D land seismic CO2 monitoring at Ketzin, Germany Peter Bergmann*, GFZ German Research Centre for Geosciences, Artem Kashubin, Schlumberger Cambridge Research, Monika Ivandic and Christopher Juhlin, Uppsala...
Abstract

Summary Difficulties encountered during the processing of the time-lapse 3D land-seismic data at the CO 2 geological storage site at Ketzin, Germany, were to a large extent attributed to changes in near-surface velocities. Two workflows for processing of the 4D data were tested. The first one included re-calculation of the refraction static corrections based on new information about the near-surface from first breaks. This workflow showed that the near-surface changes could only imperfectly be resolved by new refraction static corrections. The second workflow included cross-correlation of the traces acquired at the same locations but during different campaigns and calculation of the prestack time shifts between the surveys. Both workflows demonstrated their capability to minimize the time-lapse noise and enhance the time-lapse reservoir signature. They provide similar time-lapse results, except that the cross-correlation workflow is quicker, more accurate and displays less time-lapse noise.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1985 SEG Annual Meeting, October 6–10, 1985

Paper Number: SEG-1985-0299

... ABSTRACT No preview is available for this paper. datum

**correction**only refractor velocity calculation**refraction****static**calculation solution collapse fill final stack**refraction**traveltime refractor**static****correction**application refractor structure upstream oil & gas...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2015 SEG Annual Meeting, October 18–23, 2015

Paper Number: SEG-2015-5843046

...Seismic

**refraction****static****correction**using 3-C digital receivers in Ordos, China L. Liu, S.P. Peng, D.K. He*, L. Sun, China University of Mining & Technology (Beijing) Summary A project has been carried out using 3-C digital receivers to do the P- and S- wave near surface survey in order to provide...
Abstract

Summary A project has been carried out using 3-C digital receivers to do the P- and S- wave near surface survey in order to provide accurate near-surface velocity and thickness model for 3-C exploration. Due to lacking of a particular trigger, seismic data were acquired in a passive way. The paper expounded in details the acquisition system and developed a high-accuracy processing workflow, crosscorrelation functions are introduced to find out the time difference of passive received seismic data, arithmetical add and subtract operations are used to suppress spurious first arrivals and get purer P- and SH- first arrivals . The processing and interpretation results of the P- and SH-wave data make it possible to do the near-surface survey using a passive acquisition by 3-C digital receivers, which provides reliable P- and S-wave velocity and thickness model for the 3-C static correction. Introduction Many conventional approaches had been used to obtain the statics for both P- and S-wave data, Such as refraction survey and micro-log. In recent years, shear wave statics has caused extensive concern, P-refractions together with SV-refractions are used to calculate converted-wave statics (Schafer, 1993), share wave logging(Cao, 2006) and 3-C up-hole survey technique are widely used to detect P-wave and S-wave velocity on surface (Li, 2006) . A near-surface survey by 3-C shallow refraction had been carried out using dynamite source expounded in detail the principle using polarization analysis method for separation of P-wave from S-wave (Duan, 2008). While the circumstance that lack of a particular trigger hasn’t been discussed. In this paper, the acquisition system has no immediate response when the source exploding, we take a passive way to acquire the seismic data. According to this acquiring system we developed a high-accuracy processing workflow. The result of the experiment indicated that the 3-C digital receivers can be used to do the near-surface survey of both P- and Swave in a passive way. Acquisition The target area is located in the northeast portion of the Ordos Basin, China. We selected 2 sites to do the acquisitions. The data are received by both conventional Pwave geophones and 3-C digital ones. Conventional Prefractions have the trigger devices and can only supervise P-wave data, the source is motivated by a hammer striking downward. With the same hammer striking a horizontal shear block from both left side and right side, we get the SH (left) and SH (right) source shown in Figure 1. The Y component of the 3-C receivers is oriented to collect SH data which is the only component we concern about. The data are recorded using the combination of SERSCL- 428XL and DSU3- LINK.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1996 SEG Annual Meeting, November 10–15, 1996

Paper Number: SEG-1996-0009

... characterization variation delay time mudflow gully

**refraction****static**ACQ1.3 A successful 3-D seismic survey in the no-data zone, offshore Mississippi delta: survey design and**refraction****static****correction**processing. Charles Carvill*, Nazim Faris, and Ron E. Chambers, Western Geophysical Summary The delta...
Proceedings Papers

Publisher: Offshore Technology Conference

Paper presented at the Offshore Technology Conference, May 6–9, 1996

Paper Number: OTC-7980-MS

...@l 9 OTC 7980 A Successful 3D Seismic Survey in the No-Data Zone, Offshore Survey Design and

**Refraction****Static****Correction**Processing. Charles Carvill, Nazim Faris, and Ron Chambers, Western Geophysical Copyr#Jht 1S9S, OFFSHORE TECfiNOLOf3Y CONFERENCE This papar waa prapard for prasenlaticm at the...
Abstract

Abstract This is a success story of survey design and refraction static correction processing of a large 3D seismic survey in the South Pass area of the Mississippi delta. In this transition zone, subaqueous mudflow gullies and lobes of the delta, in various states of consolidation and gas saturation, are strong absorbers of seismic energy. Seismic waves penetrating the mud are severely restricted in bandwidth and variously delayed by changes in mud velocity and thickness, Using a delay-time refraction static correction method, we find compensation for the various delays, i.e., static corrections, commonly vary 150 ms over a short distance. Application of the static corrections markedly improves the seismic stack volume. This paper shows that intelligent survey design and delay-time refraction static correction processing economically eliminate the historic ‘no data’ status of this area. Introduction Large river deltas present unique problems for seismic exploration. Of particular interest to Gulf Coast geophysicists are the effects of the modern Mississippi delta on seismic data. Variations in the gas content and consolidation of sediments, corresponding to the mud structures of the delta, impose extreme attenuation and traveltime variations on seismic waves. These properties are responsible for designation of the delta area as a ‘no seismic data zone.’ Compensation for these effects is an important part of seismic processing. Deconvolution and spectral balancing compensate for attenuation effects, and refraction and reflection static correction processing compensate variation. Beginning in 1993, Western Geophysical solicited and obtained the participation of several oi I companies in a large 3D survey to be conducted in the area of the delta (Figure 1). This paper highlights the design and refraction static correction processing of Phase 1 of the project. Phase 2 has been acquired and is being processed. From the beginning, we realized that refraction static corrections would be crucial in processing of the survey. Previously, in refraction static correction processing of 2D shallow streamer data, we had produced results similar to those presented by Schatz, et al.] But, although we had been successful in static correction processing of both 3D land and 3D marine-streamer data, we did not know what to expect in this extreme environment. The modern Mississippi river delta has been studied extensively. A particularly useful report on studies by LSU and USGS of the soil properties and structure of the delta was presented by Coleman, et al.z Marathon Oil studied the delta and presented three papers in 1988: Tinkle, et al.3, studied acoustics of the mud structures in the delta; May, et al.4 used acoustic measurements and sediment samples to predict and help correct problems encountered in seismic data; Meeder, et al.s, constructed a velocity and depth model along a 2D profile based on borings and acoustic measurements, and compared static corrections from this model to those generated from refraction and reflection seismic data.

Proceedings Papers

Paper presented at the International Petroleum Technology Conference, January 19–22, 2014

Paper Number: IPTC-17325-MS

.... This was achieved by applying first-arrival travel time tomography to obtain the shallow velocity information needed to calculate

**refraction****statics****corrections**.**Refraction****statics**tomography uses the first break travel time picks of the seismic data to derive a velocity model of the near surface. This...
Abstract

Abstract This paper describes the refraction statics processing based on tomographic inversion of a 503km 2 subset of a modern marine 3D seismic dataset acquired in very shallow waters offshore Qatar. The objective of the seismic survey was imaging of the Mesozoic interval from 0.4 - 1.8 seconds two way travel time below sea level. Characteristic for the study area is the presence of local shoal bodies, often associated with coral reefs at sea bottom and in the near surface below sea bottom. These features can have a significant effect on the imaging of seismic data and therefore the prospectivity assessment of the exploration area as their typically high velocity introduces distortions in the timing of events, i.e. false structures might be generated or true structures suppressed. Compensating for the reef structures in the statics model results in a more accurate image of the subsurface. This was achieved by applying first-arrival travel time tomography to obtain the shallow velocity information needed to calculate refraction statics corrections. Refraction statics tomography uses the first break travel time picks of the seismic data to derive a velocity model of the near surface. This velocity model is then used to generate static shifts to correct the data to a final datum plane using a known replacement velocity, thereby removing the velocity variation caused by the sea bottom and near surface features. The tomographic inversion algorithm for land data was adapted to marine data by including a new option to freeze the water column velocity, which should be constant and not taken into account in the velocity updates. Refraction statics tomography is superior to conventional refraction statics because the inverted velocity model reveals the lateral and vertical velocity variations in the near surface. The dense shot and receiver spacing of this data set provided a large number of first break picks for the tomographic inversion process and resulted in a stable near surface velocity model. The computed static shifts corrected for some of the time shifts observed below the sea bottom features. The application of refraction statics tomography in this study provided an improved subsurface image compared to the original processing. Introduction The study area (Figure 1) is located offshore Qatar on the western flank of the Qatar Arch, a very prominent almost N-S oriented paleohigh. The morphology of the area is in general very flat without any pronounced structures or tectonic elements. Although the depositional environment was fairly stable throughout geological time, significant velocity variations in the overburden occur, either being related to facies/reservoir quality variation within the dominating carbonate rocks or as a result of subsurface features. Characteristic for the study area is the presence of local shoal bodies, often associated with coral reefs at sea bottom and in the near surface below sea bottom. These features can have a significant effect on the imaging of seismic data and therefore the prospectivity assessment of the exploration area as their typically high velocity introduce distortions in the timing of events, i.e. false structures might be generated or true structures suppressed. Compensating for the reef structures in the statics model results in a more accurate seismic image of the subsurface. The objective of this study was to improve the seismic data through the application of refraction statics tomography processing.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2015 SEG Annual Meeting, October 18–23, 2015

Paper Number: SEG-2015-5864719

... and Luo, 2004). For

**refraction**methods, the accuracy of the**refraction****static****correction**largely depends on the quality of the first arrival traveltimes. However, seismic amplitudes at far offsets are often too weak to pick. To overcome this problem, the theory of Super-Virtual Interferometry (SVI) is...
Abstract

Summary We apply interferometric theory to solve a 3D seismic residual statics problem that helps to improve reflection imaging. The approach can calculate the statics solutions without picking the first arrivals in shot or receiver gathers. The statics accuracy can be improved significantly since we utilize stacked virtual refraction gathers for calculation. Because sources and receivers can be placed at any position in a 3D seismic survey, the arrival times of virtual refractions for a pair of receivers or sources are no longer the same as in a 2D case. To overcome this problem, we apply 3D Super-Virtual Interferometry (SVI) method in the residual statics calculation. The virtual refraction for the stationary source-receiver pair is obtained by an integral along source or receiver line without the requirement of knowing the stationary locations. Picking the maxenergy times on the SVI stacks followed by applying a set of equations is able to derive reliable residual statics solutions. We demonstrate the approach by applying to synthetic data as well as real data. Introduction Rugged topography and complex near surface layers are some of the important challenges that we are facing in seismic data processing today. Residual statics due to near-surface velocity variations may not be able to be resolved through the near-surface model imaging, but critical for seismic data processing. There are many methods to calculate residual statics solutions, such as reflection stack-power maximization method (Ronen and Claerbout, 1985), refraction waveform residual statics (Hatherly et al., 1994), and refraction traveltime residual statics (Zhu and Luo, 2004). For refraction methods, the accuracy of the refraction static correction largely depends on the quality of the first arrival traveltimes. However, seismic amplitudes at far offsets are often too weak to pick. To overcome this problem, the theory of Super-Virtual Interferometry (SVI) is developed to generate headwave arrivals with improved SNR (Bharadwaj and Schuster, 2010). The SVI method is later used to calculate 2D residual statics solutions without picking first arrivals (Zhang et al., 2014). In this study, we follow Lu et al. (2014) to extend SVI to 3D and apply that to solve a 3D residual statics problem.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2009 SEG Annual Meeting, October 25–30, 2009

Paper Number: SEG-2009-0527

... geologic challenges. In the previous processing of this project, long period

**refraction****static****corrections**and short period surface consistent**static****corrections**were applied in the time domain prior to migration. Traditional**refraction****statics**solutions address the time delays caused by shallow velocity...
Abstract

Summary We present a case study of an anisotropic prestack depth migration (APSDM) project which used high-resolution, shallow tomography and anisotropic model building for a large depth migration project in the Gulf of Mexico. The enhanced work flow resulted in high quality images and more accurate placement of events, compared to previous processing in the area. The project consisted of approximately 553 OCS blocks of data in the Mississippi Canyon, South Timbalier, Ewing Bank, Grand Isle, Grand Isle South Addition and Ship Shoal South Addition areas (Figure 1). The goals of this project were to produce a more accurate velocity model which would enhance event placement and improve the imaging of steep dips, salt boundaries, and subsalt events. To this end, the low velocity South Timbalier trench area which was previously addressed via refraction statics was modeled using tomographic velocity inversion to produce a more accurate shallow velocity field. Additionally anisotropic prestack depth migration was employed to better tie the seismic events with well information. Introduction This survey is located in an area of the Gulf of Mexico with many complex surface structures and geologic challenges. In the previous processing of this project, long period refraction static corrections and short period surface consistent static corrections were applied in the time domain prior to migration. Traditional refraction statics solutions address the time delays caused by shallow velocity anomalies via static shifts. The slow velocity layer that is solved in the refraction solution will cause “sags” in the resultant seismic image due to the longer travel times through the slow velocity layer. The refraction solution solves for the traveltime delay induced by the layer and applies a static shift to the traces so as to minimize the resultant time sag. While these static shifts generally produce much improved time images deeper in the section, the time static applied is not kinematically correct for depth migration. In particular, this could lead to velocity distortions when solving for the depth velocity field. While reviewing the velocity modeling approach for this project, it was decided that a high-resolution tomographic inversion would be attempted to more correctly model the velocities in the South Timbalier trench area. If correctly modeled, a more stable velocity field and a more accurate depth image should be expected. It was not presumed that tomography could resolve the high frequency nature of the surface consistent residual statics that had been applied, so this part of the premigration data preparation was retained. The other key enhancement to the previous processing flow was the use of anisotropic prestack depth migration. Through the use of abundant checkshot velocity information (539 checkshots) and anisotropic parameter estimation, well-calibrated velocities could be used for migration. The use of a calibrated velocity field should ensure better well ties with seismic data. Initial Anisotropic Model Building A total of 539 checkshots were analyzed for use as a starting point for building the initial velocity model. The checkshot velocity functions were analyzed and spurious trends were edited. These edited checkshot velocities were gridded, interpolated and smoothed to generate the initial vertical velocity model Vz.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2014 SEG Annual Meeting, October 26–31, 2014

Paper Number: SEG-2014-1258

...

**static****correction**method reservoir characterization seg denver 2014 propagation shear wave wave**static****correction**application receiver point single shot record viscoelastic modeling modeling**refraction**ppp wave**correction**upstream oil & gas trace number velocity model**static**...
Abstract

Summary Visco-elastic wave equation forward modeling is used to simulate propagation of refraction wave in the near surface layers. Based on the propagation rules figured out from forward modeling, the converted refraction can be identified and analyzed to obtain the information of near-surface shear wave. We develop the improved converted refraction static correction method which can approximate the shear wave receiver statics more accurately. Besides, this is an economical method because it can be applied to calculate the converted wave statics without knowing the velocity of near-surface shear wave. The effectiveness of this method has been demonstrated by synthetic data processing results.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the SEG International Exposition and Annual Meeting, October 11–16, 2020

Paper Number: SEG-2020-3427893

... processing in this area, and it is also the basis of subsequent seismic data processing. In view of the serious

**static****correction**problem in the Loess Plateau area of Ordos Basin, this paper proposes the fusion**static****correction**technology. Firstly, the tomographic**statics**and**refraction****statics**are...
Abstract

The surface structure of Loess Plateau in the south of Ordos Basin is complex, and the problem of static correction is very serious. How to effectively solve the problem of static correction in Loess Plateau area is the primary task and one of the main technical difficulties of seismic data processing in this area, and it is also the basis of subsequent seismic data processing. In view of the serious static correction problem in the Loess Plateau area of Ordos Basin, this paper proposes the fusion static correction technology. Firstly, the tomographic statics and refraction statics are decomposed into high-frequency component and low frequency component respectively, and then the high frequency component and low-frequency component are optimally combined again based on the imaging effect and structural form, so as to a new set of statics is obtained. The fusion static correction technology integrates the advantages of tomographic static correction technology and refraction static correction technology. The practical application results show that fusion static correction technology can achieve the best static correction effect when solving the static correction problem of seismic data in Loess Plateau area, so it is an effective method to solve the static correction problem in Loess Plateau area of Ordos Basin. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 1:50 PM Presentation Time: 2:40 PM Location: Poster Station 5 Presentation Type: Poster

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2018 SEG International Exposition and Annual Meeting, October 14–19, 2018

Paper Number: SEG-2018-2997135

... JARR method was successful at providing accurate

**static****corrections**to enhance reflections in the data. Presentation Date: Wednesday, October 17, 2018 Start Time: 1:50:00 PM Location: Poster Station 6 Presentation Type: Poster ivanov a-priori information velocity model**refraction**...
Abstract

Joint analysis of refractions and reflections (JARR) was designed to address difficulties associated with processing near-surface data. Near-surface complexity is primarily responsible for statics issues in seismic data. To address statics concerns, a-priori information (e.g., well logs and check shots) is usually required tocalculate time shifts to fix the data. In this research, JARR was tested on a dataset collected along Highway 61 near Inman, Kansas. Statics were applied by using the velocity model derived from the JARR method to improve the near-surface seismic characteristics. The JARR method was successful at providing accurate static corrections to enhance reflections in the data. Presentation Date: Wednesday, October 17, 2018 Start Time: 1:50:00 PM Location: Poster Station 6 Presentation Type: Poster

Proceedings Papers

Publisher: Offshore Technology Conference

Paper presented at the Offshore Technology Conference, May 2–5, 1988

Paper Number: OTC-5755-MS

... ABSTRACT Near surface

**statics**are a major problem in modern delta fill areas such as the Mississippi. The necessary travel time**corrections**can be determined by manual techniques,**refraction**analysis, and modeling of the Holocene sediments. Sediment characteristics from direct measurements are...
Abstract

ABSTRACT Near surface statics are a major problem in modern delta fill areas such as the Mississippi. The necessary travel time corrections can be determined by manual techniques, refraction analysis, and modeling of the Holocene sediments. Sediment characteristics from direct measurements are discussed in companion papers and have been related to dynamic seafloor features. Seismic models based on this information provided statics corrections for two sample data sets. Results of the modeling are compared to refraction analysis and manual reflection statics. The combined use of modeling and direct measurement information to compute near surface seismic statics corrections can provide improved seismic sections. INTRODUCTION Work in the 1970's, especially that utilizing side-scan sonar, delineated a wide variety of sub-aqueous landslide features, which cause the irregular sea-bottom topography of the offshore Mississippi Delta. Physical loading by delta-front sand over prodelta clay, plus cyclic loading by storm waves, initiate sediment failure and downslope flow. Delta-front failure begins in the updip collapse depressions, which yield sediment that slowly flows down-slope through mudflow gullies. Between the gullies are remnant highs, the interflow platforms. The mudflows spread out downdip upon the outer continental shelf as coalescing lobes. These features and processes are discussed in a companion paper (May et al., 1988). Anomalous seismic velocities are associated with these mudflow features (Tinkle et al., 1988) and cause near surface seismic travel time anomalies, or statics. The thickest anomalous zones occur where rapid input of fine-grained, organic rich sediment results in excess pore fluids and biogenic gas buildup. The lowest seismic velocities arise when these overpressured, underconsolidated sediments fail (May et al., 1988). Physical agitation and release of overburden pressure during mass flow apparently liberates interstitial gas into bubble phase, producing maximum seismic attenuation and lowest velocities. These characteristics of the unstable seafloor inhibit our ability to acquire interpretable seismic data. The extent of this "seismic no-data zone" (Figure 1) was outlined by Garrison (1974). A standard technique on land to make the necessary time corrections is refraction statics. This method can be used offshore, but in this case is also problematic. Raytrace seismic modeling, based on the in situ interval velocity measurements, indicates seismic source to receiver offsets greater than 10,000 feet are necessary to record first break refract ions from the base of the near surface seismically anomalous zone. Sample shot records verify these predictions (Figure 2). Note the large magnitude of the short period statics (trace-to-trace time shifts) at 8000 feet offset on the 1eft and at 7000, 8200, and 10700 feet on the righthand shoft record. Long period (areal dip) statics are evident by the extreme variation in refraction cross-over distance between the two shot records from the same 1ine. Statics shifts of this magnitude, in areas of poor signal quality, are too large for automatic statistical techniques to reliably solve.

Proceedings Papers

Publisher: Society of Petroleum Engineers (SPE)

Paper presented at the SPE Middle East Oil & Gas Show and Conference, March 6–9, 2017

Paper Number: SPE-184029-MS

... trace over multiple offset classes and inverted for surface consistent source and receiver

**corrections**. Surface consistent analysis of the**refraction**data in the XYOA domain is fully automatic and provides a robust solution in the presence of noise, enhancing subsequent reflection residual**statics**...
Abstract

We describe two novel technologies developed for seismic characterization of the complex near surface in Saudi Arabia. Current exploration efforts in the Arabian Peninsula are directed at the identification of low-relief structures and stratigraphic traps where most of the major structures (giant and supergiant reservoirs) have been already identified and are under production. The near surface in arid environments such as Saudi Arabia is affected by anomalies caused by karsting, sand dunes and wadis that introduce severe distortions in seismic wave propagation into the subsurface. These distortions cause apparent false structures in the final stacked image that can be erroneously drilled. Two technologies were recently developed by Saudi Aramco to be able to obtain reliable seismic images of deep and low-relief reservoirs. The technologies consist of helicopter-borne transient electromagnetics (HTEM) in joint inversion with seismic, and a novel surface consistent solution for statics using refracted waves named pQC (from the QC analysis of first break (FB) traveltimes: picks). The TEM technology is based on the transmission of a primary electromagnetic signal through a large moment magnetic dipole source and the reception of a secondary magnetic field deriving from the interaction of the primary field with the earth. The acquisition is performed with a helicopter allowing to acquire data with exceptional spatial density and speed. The velocity modeling of the near surface is obtained by in-house developed joint inversion algorithms allowing to integrate the high resolution TEM information into the velocity reconstruction of the near surface. The pQC technology consists of a surface consistent statics solution using refraction data. The high-resolution time delays are calculated by means of cross-correlation of early arrival waveforms that are inverted for surface consistent time delays. This method provides detailed images of the near surface time corrections in a fraction of the time needed by conventional workflows currently used in the seismic industry. The two newly developed technologies are applied to a complex wadi structure in central Saudi Arabia where conventional seismic data analysis approaches fail. The 3D TEM seismic joint inversion solves the long wavelength of the wadi structure while the high-resolution/medium wavelength time correction is obtained by pQC. The combined time corrections of the near surface enable accurate imaging of deep structures important for reserves evaluation. The joint inversion technology with airborne TEM acquisition systems and the surface consistent refraction analysis (pQC) provide innovative solutions for imaging low-relief structures in exploration and field development applications.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1985 SEG Annual Meeting, October 6–10, 1985

Paper Number: SEG-1985-0295

... ABSTRACT No preview is available for this paper.

**refraction**theory linear inversion**refraction**method**correction****static****correction**near-surface model model parameter annual seg meeting gli method upstream oil & gas application modeling iteration reservoir...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1986 SEG Annual Meeting, November 2–6, 1986

Paper Number: SEG-1986-0277

... data quality. They handle the short period problems well, but cannot solve the long period problems. Sections will look better, but may show erroneous structure.

**Refraction****statics**can be used to solve long period problems and help produce optimum sections showing**correct**structure.**Refraction**picking...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2017 SEG International Exposition and Annual Meeting, September 24–29, 2017

Paper Number: SEG-2017-17738085

... Location: 370C Presentation Type: ORAL seg seg international exposition annual meeting maximization velocity model

**correction**surface velocity model coherence reservoir characterization algorithm upstream oil & gas cost function**static****correction****refraction****static**processing flow...
Abstract

ABSTRACT Near surface models from refraction inversion contain several types of errors, which are partially compensated later in the data flow by reflection residual statics. In this work, we modify the dataflow to automatically include feedback information from reflection statics from stack-power maximization. This technique can work with any model based refraction solutions including grid based tomography model and layer based delay time methods. In this report we modify cost function of the refraction inversion by adding model and data weights computed from the long wavelength components of surface consistent residual statics. By using an iterative inversion, these weights allow us to update the near surface velocity model and to reject first arrival picks that do not fit the updated model. In this non-linear optimization work flow the refraction model is derived from maximizing the coherence of the reflection energy and minimizing the misfit between model arrival times and the recorded first arrival times. This approach can alleviate inherent limitations in shallow refraction data by using coherent reflection data. Presentation Date: Thursday, September 28, 2017 Start Time: 8:30 AM Location: 370C Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016

Paper Number: SEG-2016-13843875

... : Geophysics , 41 , 922 – 938 . 10.1190/1.1440672 . surface consistent

**refraction**method**correction**tomographic solution application surface-consistent**refraction**solution**static**model reservoir characterization geophysics surface-consistent**refraction**method upstream oil & gas...
Abstract

ABSTRACT A novel, fully automated surface-consistent solution for refracted waves, is developed to solve for a combination of long and short wavelength statics at the early stages of seismic data processing. The method is very efficient in terms of computing resources and dramatically reduces the turnaround time for deriving near-surface corrections. A new sorting domain for seismic traces in the common midpoint (CMP)-offset-azimuth (XYOA) domain enables the collection and the statistical analysis of large volumes of refraction data in terms of first break times (FB) and of early arrival waveforms. The theory for surface-consistent analysis of reflected waves is adapted to the case of refracted waves and applied in the XYOA sorting domain. The refraction-based surface-consistent approach is applied to different land surveys in central Saudi Arabia showing challenging near-surface conditions. The surface-consistent refraction approach is benchmarked against a near-surface tomographic solution from a commercial software package. Three examples corresponding to karsts, thick sand dunes and a wadi structure are analyzed. The automatic refraction surface-consistent solution always provides superior results when compared to the benchmark tomographic case. The surface-consistent refraction approach results in a new, fully automated and robust method to solve for near surface complexities. Presentation Date: Monday, October 17, 2016 Start Time: 3:45:00 PM Location: 150 Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2017 SEG International Exposition and Annual Meeting, September 24–29, 2017

Paper Number: SEG-2017-17557867

... upstream oil & gas automatic near-surface velocity velocity model application seg seg international exposition wavelength

**static****refraction**data anomaly**correction**long wavelength**static**medium wavelength reservoir characterization**refraction**residual**static**colombo calculation...
Abstract

ABSTRACT Recent trends in exploration of the Middle East layered geology have shifted toward the identification of subtle stratigraphic closures and low-relief structures, which can potentially hold significant amounts of hydrocarbons. The delineation of such structures requires the robust solution of the near-surface velocity complexities. Consistency of processing workflows and of near-surface solutions among nearby blocks is another important requirement. We apply the recently developed methodology of surface-consistent analysis of refraction data to a large merge of seismic blocks (mega-merge) from Central Saudi Arabia. The objectives are to enhance the near-surface modeling and to provide robust solutions for seismic data acquired over several years using variable acquisition parameters. The near-surface velocity model is obtained by automatic processing of about 20 billion first break arrival times that are transformed to depth-domain, and common mid-point (CMP) velocity functions. The surface-consistent refraction residuals are obtained automatically to solve medium wavelength statics not accounted for by reflection residual statics. Comparison with other methods suggest that the developed approach is superior in quality and robustness for solutions of a variety of near-surface geologic conditions. Presentation Date: Thursday, September 28, 2017 Start Time: 8:55 AM Location: 370C Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Petroleum Engineers (SPE)

Paper presented at the International Oil and Gas Conference and Exhibition in China, November 7–10, 2000

Paper Number: SPE-64741-MS

...-surface make the travel time of seismic waves distorted. It is difficult for low S/N data to stack. So the accuracy of seismic exploration results is seriously influenced by

**static****correction**problems. Field**static****correction**methods, such as minor**refraction**and micro-log, can control the low frequency...
Abstract

Abstract In view of large residual static correction values after field static correction in complex areas, the field near-surface data and field static correction data are used as the initial condition of the method. The first break time is used for the basic constrain of the method. The residual time shifts can be determined in common-shot, common-receiver and common-offset domains. Thus, the global optimized residual static correction values are estimated by doing statistics of a great deal of data and by making orthogonal iteration and step-by-step approximation. After being repeatedly revised, this result plus datum correction values forms the final static correction values. This paper takes actual data as example to show the good application results of this method. Introduction In western China, the conditions of surface geology are very complex. The complex structures of the near-surface make the travel time of seismic waves distorted. It is difficult for low S/N data to stack. So the accuracy of seismic exploration results is seriously influenced by static correction problems. Field static correction methods, such as minor refraction and micro-log, can control the low frequency values well. But in complex areas, the large residual static correction values are also present after field static correction. Automatic residual static correction methods, based on reflection, only get small high-frequency static correction values. At the same time, it requires certain S/N. On the basis of classical refraction theory, the static correction methods by making an inversion near-surface model, (such as delay time method, extended generali-zed reciprocal method), require choosing true first break travel time, and must trace a common high velocity refraction layer. It is difficult to apply for whole work area in complex areas. Our 2D/3D method in this paper takes the first break time of the refraction wave as the basic constraint, and uses a global optimized algorithm on the basis of field static correction. It needs no true first break time of the refraction wave, and does not need trace a common refraction layer in the full work area, and also does not need to know the velocity and thickness of the overlying formation. It results in good effect for solving the big residual static correction problem in complex areas. Method and Theory 2D multi-domain iteration statics(2D MDIS). The basic idea of the method. On top of the high velocity layer, when the static correction values caused by low-descending velocity zone are accurately removed, the first break time should be smoothing in common shot, common receiver and common offset domains. This is the premise and foundation of the method. Our basic idea is that we first roughly adjust and then finely adjust. First, the field near-surface data and field static correction data are used as the initial condition of the method. A large quantity of first break data is used to estimate statics by taking the top of a high velocity layer as the datum. Then the residual time shifts in the common shot, common receiver and common offset domain can be known respectively because static correction errors exist. Step-by-step approximation and multiple iteration are used to transform the residual time shifts to residual statics of every shot and receiver. Finally, estimated statics are combined with datum correction values as a final statics. The fulfillment course of the method. Pickup first break of survey lines. In reasonable offset scope, an automatic and interactive manner is used to pick up a refraction first break of the high velocity layer of survey line. First break of the same off-set of survey line must trace the same phase. Crosslayer to and fro is not permitted. Estimation of initial statics. There are two ways for initial statics estimation. One way is that we use field statics files to separate out high layer statics and datum statics. The other is that we use the model method to interpolate high velocity layer statics of the survey line and datum statics on the base of field surface data. Latter static correction iteration calculation will be fulfilled by taking statics of top of the high velocity layer as initial statics. 2D multi-domain iteration statics(2D MDIS). The basic idea of the method. On top of the high velocity layer, when the static correction values caused by low-descending velocity zone are accurately removed, the first break time should be smoothing in common shot, common receiver and common offset domains. This is the premise and foundation of the method. Our basic idea is that we first roughly adjust and then finely adjust. First, the field near-surface data and field static correction data are used as the initial condition of the method. A large quantity of first break data is used to estimate statics by taking the top of a high velocity layer as the datum. Then the residual time shifts in the common shot, common receiver and common offset domain can be known respectively because static correction errors exist. Step-by-step approximation and multiple iteration are used to transform the residual time shifts to residual statics of every shot and receiver. Finally, estimated statics are combined with datum correction values as a final statics. The fulfillment course of the method. Pickup first break of survey lines. In reasonable offset scope, an automatic and interactive manner is used to pick up a refraction first break of the high velocity layer of survey line. First break of the same off-set of survey line must trace the same phase. Crosslayer to and fro is not permitted. Estimation of initial statics. There are two ways for initial statics estimation. One way is that we use field statics files to separate out high layer statics and datum statics. The other is that we use the model method to interpolate high velocity layer statics of the survey line and datum statics on the base of field surface data. Latter static correction iteration calculation will be fulfilled by taking statics of top of the high velocity layer as initial statics. The basic idea of the method. On top of the high velocity layer, when the static correction values caused by low-descending velocity zone are accurately removed, the first break time should be smoothing in common shot, common receiver and common offset domains. This is the premise and foundation of the method. Our basic idea is that we first roughly adjust and then finely adjust. First, the field near-surface data and field static correction data are used as the initial condition of the method. A large quantity of first break data is used to estimate statics by taking the top of a high velocity layer as the datum. Then the residual time shifts in the common shot, common receiver and common offset domain can be known respectively because static correction errors exist. Step-by-step approximation and multiple iteration are used to transform the residual time shifts to residual statics of every shot and receiver. Finally, estimated statics are combined with datum correction values as a final statics. The fulfillment course of the method. Pickup first break of survey lines. In reasonable offset scope, an automatic and interactive manner is used to pick up a refraction first break of the high velocity layer of survey line. First break of the same off-set of survey line must trace the same phase. Crosslayer to and fro is not permitted. Estimation of initial statics. There are two ways for initial statics estimation. One way is that we use field statics files to separate out high layer statics and datum statics. The other is that we use the model method to interpolate high velocity layer statics of the survey line and datum statics on the base of field surface data. Latter static correction iteration calculation will be fulfilled by taking statics of top of the high velocity layer as initial statics. Pickup first break of survey lines. In reasonable offset scope, an automatic and interactive manner is used to pick up a refraction first break of the high velocity layer of survey line. First break of the same off-set of survey line must trace the same phase. Crosslayer to and fro is not permitted. Estimation of initial statics. There are two ways for initial statics estimation. One way is that we use field statics files to separate out high layer statics and datum statics. The other is that we use the model method to interpolate high velocity layer statics of the survey line and datum statics on the base of field surface data. Latter static correction iteration calculation will be fulfilled by taking statics of top of the high velocity layer as initial statics.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2010 SEG Annual Meeting, October 17–22, 2010

Paper Number: SEG-2010-2004

... time is a necessary parameter which we cannot know exactly because of the shooting depth. It is necessary for us to

**correct**underground shot points to the surface with uphole time so as to obtain exact reciprocal time and then to improve**refraction**delay time and**static**precision. For the iterative...
Abstract

Summary Because the shooting positions are always located at certain depth when using a dynamite source, it may bring certain errors in first arrival refraction statics, thus damaging seismic imaging quality. This paper theoretically analyzes why incorrect up-hole time may bring static errors, proposes solutions and directs further research based on the analysis of impact on real seismic data. This will be helpful for field acquisition guidance, improving the accuracy of present first arrival statics calculations, as well as perfecting the first arrival refraction statics method. Introduction The depth of dynamite shooting varies from several meters to dozens of meters generally, so the shot and receiver points are not at the same datum. This may result in obviously unreasonable delay time using the Generalized Reciprocal Method (GRM) or iterative method. For GRM method, reciprocal time is a necessary parameter which we cannot know exactly because of the shooting depth. It is necessary for us to correct underground shot points to the surface with uphole time so as to obtain exact reciprocal time and then to improve refraction delay time and static precision. For the iterative method, in order to get better delay time through iterative calculation, the method mentioned above is also necessary. Therefore, uphole time is a key parameter for improving the accuracy of refraction statics. Here, the uphole time is the vertical travel time of the seismic wave from the borehole shooting position to the surface. We will focus our discussion on how to ensure uphole time accuracy, and how to improve precision of first arrival refraction statics and seismic data imaging. Theoretical analysis The first arrival refraction statics method is a conventional and fairly good solution for static problems. In the application of this method, the key parameter which affects the precision of statics is the refraction delay time. Therefore, as long as we get a better delay time, the application of the first arrival refraction method is basically successful. Common ways for calculating delay times are the reciprocal and iterative methods. It can be seen from formula (1) that the reciprocal time between A and C is needed in the GRM method for delay time calculation. When A and C are located at a certain depth underground, we cannot record the reciprocal time between A and C in the field. The only way for calculating delay time with formula (1) is to correct the positions of the shot points to the surface then to get the reciprocal time between A and C. In addition, assuming B is a receiver point, A and C are the shooting and receiving points, we know from formula (1) and figure 1 that if the uphole time is incorrect, it will affect the delay time precision of shooting and receiving points at the same time. During the calculation of delay time in the iterative method, first shift the shooting position to the surface with uphole time, then separate the delay time to shot and receiver points afterward.

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