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#### Static corrections, statics

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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 2017 SEG International Exposition and Annual Meeting, September 24–29, 2017

Paper Number: SEG-2017-17585227

... ABSTRACT We present a method to

**correct**for intra-array**statics**and phase variations pre-stack trace ensembles intended for local summation. We apply the proposed approach as an additional step before summing traces via supergouping.**Corrections**are derived from beamforming techniques applied...
Abstract

ABSTRACT We present a method to correct for intra-array statics and phase variations pre-stack trace ensembles intended for local summation. We apply the proposed approach as an additional step before summing traces via supergouping. Corrections are derived from beamforming techniques applied in the short-time Fourier transform (STFT) domain performed independently for each frequency component. Beamforming allows to handle more complex variations of recorded signals than simple relative time shifts from trace to trace. Phase correction weights are calculated using SVD of the data matrix in the STFT domain. The proposed approach is demonstrated on synthetic and complex 3D land data from Saudi Arabia. Presentation Date: Thursday, September 28, 2017 Start Time: 9:45 AM Location: 360A Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2020-3426918

... Most short-wavelength

**statics**-**correction**methods are based on the surface-consistency assumption depending on locations of sources and receivers at the surface. Even though this assumption may work in practice, it is not the most accurate solution since raypaths in the near-surface are not...
Abstract

Most short-wavelength statics-correction methods are based on the surface-consistency assumption depending on locations of sources and receivers at the surface. Even though this assumption may work in practice, it is not the most accurate solution since raypaths in the near-surface are not strictly vertical. Existing non-surface-consistent residual statics correction methods require constructing pilot traces or picking horizons, which make them prone to errors. We propose a low rank-based residual statics correction framework (LR-Res) that estimates non-surface-consistent statics from monochromatic frequency slices in the midpointoffset transform domain in an iterative and multi-scale fashion. When land seismic data contains gaps, an additional layer of complexity arises because interpolating the data suffers as residual statics break the data’s continuity. To reconstruct densely-sampled data, we utilize ideas from our proposed LR-Res framework to jointly correct for short-wavelength statics and interpolate the data. We demonstrate the performance of our proposed methods in accurately correcting for non-surface-consistent, short-wavelength statics of densely sampled data, as well as reconstructing densely sampled data from subsampled data affected by short-wavelength statics, which we also compare with conventional methods. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 8:30 AM Presentation Time: 10:10 AM Location: 362D Presentation Type: Oral

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 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

... 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...
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 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: Society of Exploration Geophysicists

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

Paper Number: SEG-2018-2986560

... ABSTRACT Near-surface velocity models for

**static****corrections**are usually derived from critically-refracted arrivals. In the processing of P-to-S converted-wave data, critically-refracted S-waves are difficult to identify since they are usually overwhelmed by the surface-wave train which...
Abstract

ABSTRACT Near-surface velocity models for static corrections are usually derived from critically-refracted arrivals. In the processing of P-to-S converted-wave data, critically-refracted S-waves are difficult to identify since they are usually overwhelmed by the surface-wave train which propagates at similar velocities. Here we exploit the differences in the moveout of convertedwave events to compute a velocity model for the near-surface and its corresponding static effects. These effects are derived by crosscorrelating receiver gather data transformed to the t- domain. The t-differences between receiver locations is then used in an inversion process to compute a near-surface velocity model. This velocity model can be used for building migration velocity models or to initialize elastic full waveform inversions. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 213A (Anaheim Convention Center) 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-2017-17632009

... complex environments compel us to look for ways to overcome these assumptions as they are violated. Using the depth migration velocity model, we apply an offset dependent traveltime summation as the moveout

**correction**for reflection**static**calculations in depth imaging. Presentation Date: Wednesday...
Abstract

ABSTRACT When seismic data are used to image the subsurface, assumptions and calculations are made about the near-surface to overcome the uncertainty of the velocities in the low velocity layer. A near-surface velocity model is generated to calculate a time shift that is used to correct for velocity anomalies in the near-surface for time migration. Reflection statics are calculated because often the lack of detailed near-surface information leads to inaccuracies. A normal moveout (NMO) velocity field is picked and applied to stack the data in preparation for the reflection statics calculations. The NMO equation based on the assumption that the moveout can be approximated by a hyperbola. However, the accuracy of this assumption is valid when the moveout on data is near-hyperbolic and deviates when the moveout is more complicated. A few scenarios of non-hyperbolic moveout are when the topography isn't flat, strong lateral heterogeneity of velocity is present, and when there are variations in the seismic weathering thickness and velocities. Raytracing in depth migration has overcome many of the issues with the assumptions in time migration. Foothills datasets and other geologically complex environments compel us to look for ways to overcome these assumptions as they are violated. Using the depth migration velocity model, we apply an offset dependent traveltime summation as the moveout correction for reflection static calculations in depth imaging. Presentation Date: Wednesday, September 27, 2017 Start Time: 10:10 AM Location: 370C Presentation Type: ORAL

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 Exploration Geophysicists

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

Paper Number: SEG-2016-13962619

.... , and P. Sava , 2015 , Scalar imaging condition for elastic reverse time migration : Geophysics , 80 , no. 4 , S127 – S136 , 10.1190/geo2014-0453.1 . McMechan , G. A. , and H. W. Chen , 1990 , Implicit

**static****corrections**in prestack migration of common-source...
Abstract

ABSTRACT Static corrections for multicomponent data are traditionally carried out separately for each component, i.e., applying P-wave statics on the vertical component and converted wave statics on the horizontal components. Such process will typically introduce time-shifts among components since the statics for P- and converted-waves are always different, which can distort elastic waveform in the record and thereby undermine elastic reverse-time migration images. Considering the impact on elastic reverse-time migration images caused by traditional static corrections, we propose joint static corrections for multicomponent data and develop two methods to implement joint static corrections. The first method applies statics estimated using traditional methods to multicomponent P-wave and S-wave records, separately, and obtains the corrected elastic data by merging the results. The second method extrapolates the multicomponent data from the surface to the datum in an elastic model using the elastic wave equation. A synthetic example verifies the effectiveness of the proposed method. Presentation Date: Wednesday, October 19, 2016 Start Time: 8:25:00 AM Location: Lobby D/C Presentation Type: POSTER

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2015-5830865

... sufficient to support the vertical ray-path assumption conventionally used for computation of

**static****corrections**. Cova et al. (2014) showed that even if the velocity contrast at the base of the near surface is large, the presence of dip on this interface may cause raypath-dependent delays that may differ...
Abstract

Summary When velocity contrasts at the base of the near-surface zone are small, or when the base shows some degree of structural complexity, delay times of wavefronts transmitted through this zone may become raypath dependent. Due to the low velocity of S-waves this dependency can be translated into significant non-stationary delays. In order to remove this effect we transform the data into a domain in which amplitudes are a function of the raypath angle. Processing the statics in the t- p domain achieves this goal. The t- p transform automatically scans the data and captures the intrinsic ray parameter values that represent the data. This idea was implemented and tested on synthetic and field data using an interferometric approach. Results showed that after removing the statics in the t- p domain the stacking power and coherency of the events were significantly improved. Artifacts and resolution of the t-p transform still need to be addressed to improve this method. Introduction In processing multicomponent seismic data on land and on the ocean bottom, proper treatment of the effects of a complex near surface is a critical step. This is increasingly true as acquisition of broadband, wide-azimuth seismic data becomes the norm, and as the potential for full waveform inversion of land data becomes real, requiring both modelling of waves in the near surface and accurate accounting for surface wave modes. We seek an improvement in the converted wave statics solution not only to improve imaging, but also to extend the physical completeness of the earth model. Within the context of seismic reflections, static time delays are the product of low-velocity sediments present near the surface. Changes in the velocity and thickness of these sediments introduce additional delays in the reflection traveltimes which disturb the actual shape and alignment of the subsurface reflections. This problem is magnified in the case of converted wave data due to the very low velocities of shear waves. Furthermore, the shear wave velocity contrast at the base of the near surface layer may not be sufficient to support the vertical ray-path assumption conventionally used for computation of static corrections. Cova et al. (2014) showed that even if the velocity contrast at the base of the near surface is large, the presence of dip on this interface may cause raypath-dependent delays that may differ significantly from the vertical traveltimes.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2009-1406

...

**correction**tomography upstream oil & gas joint application short wavelength**static**reservoir characterization multi-domain iteration**static**residual**static****correction**wavelength**static**seg houston 2009**static****correction**international exposition**static**problem high frequency...
Abstract

Summary In areas with thick and complex low velocity layer (LVL), statics problem is one of the key issues. Tomography method can be used to solve long wavelength statics problem, however short wavelength statics problem is still there. With multi-domain statics method, short wavelength statics problem in areas with complex LVL can be solved, but long wavelength statics problem still exists. This paper put forward a method of joint application of tomography and multi-domain static corrections. Because advantages of both methods are jointly utilized, statics problems in several areas with thick and complex LVL are successfully solved. Introduction In areas with thick LVL, tomography inversion can be applied to get a reasonable velocity model and long wavelength statics can be successfully calculated by using of this model, as suggested in previous studies. (Feng et al., 2006) However, static corrections of short wavelength in complex near surface areas cannot be accurately calculated based on the inversed velocity model because the mesh size is larger than the group interval. Usually residual statics method is applied to compute short wavelength statics, but S/N ratio of seismic data should be high enough and the residual statics must be less than half of the period of the reflection wave. (Mike Cox, 1999, p.347) These two requirements are difficult to meet simultaneously. With strong energy and high S/N ratio, first arrivals are effective and low cost information for calculation of short wavelength statics. Practical application shows that for seismic imaging, statics obtained by first arrivals are obviously better than that obtained by other methods. Multi-domain iterative statics is the commonly used method. With this method, the problem of short wavelength statics can be solved through optimized processing of common shot gather, common receiver gather (CRP), common midpoint gather (CMP) and common offset gather. This paper proposes a joint application method in which the long wavelength statics can be computed by using of tomography method while the short wavelength statics can be calculated by multi-domain iterative method. Results show that the accuracy of short wavelength statics is improved. New residual statics of shots and receivers can be obtained in various domains after iteration. This process continues until optimal static corrections are achieved. Technical discussion Multi-domain iterative statics is conducted based on field statics. High frequency components of statics for both shots and receivers can be obtained through iterations of many times of first arrivals on common shot gather, common receiver gather, common midpoint gather and common offset gather. Therefore the best first arrival corrections can be achieved in four domains. In general, first arrivals should be in a straight line or a smooth curve after application of static corrections. In many cases, however, first arrivals are still oscillatory after tomography statics, indicating there are some residual statics left. The accuracy of statics can be improved via complementing residuals to the corresponding statics. Our idea is using curve fitting for the first break static corrections to get time residuals, which are just the residual static corrections at receivers.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2015-5906814

... Summary A method for receiver

**statics****correction**of converted waves ( PS -waves) is proposed here. It is based on the observation that the**static**time delay on PS -wave events between two adjacent receivers, after the source**statics****correction**has been applied, should correspond mostly to...
Abstract

Summary A method for receiver statics correction of converted waves ( PS -waves) is proposed here. It is based on the observation that the static time delay on PS -wave events between two adjacent receivers, after the source statics correction has been applied, should correspond mostly to the differential receiver statics. The surface consistent statics model provides the theoretical framework. Adjacent Common Receiver Gathers (CRG) are crosscorrelated to obtain their time delay, namely their differential receiver statics. Stacking of PS -waves is not required, therefore the method does not depend on Vc (stacking velocity for converted wave), neither does it assume a simplified PS -wave stacking model. Application of receiver statics computed using this method on both synthetic and real data yielded encouraging results. Introduction The statics correction aims to overcome the delay caused by the near surface layer (NSL) on seismic waves reflected from deeper layers. Since S -waves propagate more slowly than P -waves and are more affected by the NSL heterogeneity, their statics correction becomes more critical and difficult to obtain. S-waves correspond to the receiver statics correction in converted wave ( PS -wave). Several methods have been proposed for the PS-wave receiver statics correction, which can be grouped into two main approaches (Cox, 1999): methods that require a NSL velocity model (datum statics) and methods based on the surface consistent model, analogous to the P -wave residual statics. The methods based on the NSL velocity model appear less accurate than what is required and the picking of events is frequently challenging (Schafer, 1993; Al-Dulaijan and Stewart, 2010). The methods based on the surface consistent model are more popular (Harrison 1992, Cary and Eaton 1992) since they show the capability for short wavelength statics resolution. They require PS-wave reflections to be stacked and the calculation is frequently cumbersome and laborious. An alternative approach to obtain the receiver statics correction for PS data is proposed in this paper. It is carried out on surface receiver gathers using data without NMO correction, based on the principle that all the PS -wave events of a common receiver gather are affected by the same S -wave static delay. Related techniques for conventional seismic data statics using prestack data in the surface domains Common Receiver Gather (CRG) and Common Shot Gather (CSG) can be found in Disher and Naquin (1970) and Cox (1999). The method’s principles and tests with synthetic and real data are presented in the following sections.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2013 SEG Annual Meeting, September 22–27, 2013

Paper Number: SEG-2013-1078

... SUMMARY For the last 30 years, co-located transient EM soundings have been the preferred method for

**correcting**apparent MT**static**shift. We show that this combination can produce fallacious results, and that, with modern broad-band MT instrumentation, complete modeling of the topography is...
Abstract

SUMMARY For the last 30 years, co-located transient EM soundings have been the preferred method for correcting apparent MT static shift. We show that this combination can produce fallacious results, and that, with modern broad-band MT instrumentation, complete modeling of the topography is more likely to give a correct image of the subsurface.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2013 SEG Annual Meeting, September 22–27, 2013

Paper Number: SEG-2013-0003

... geophysics seismic line reservoir characterization multiple layer model layer model inversion saudi arabia government bridle

**static****correction**saudi aramco**static**solution shallowest layer annual international meeting seg houston 2013 upstream oil & gas initial multiple layer...
Abstract

Summary Multiple layer near-surface models for 2D lines can be constructed from uphole control. Time anomalies may still be present in the static solution due to the sparse sampling of the near-surface by the upholes. The anomalies are solved by additional shifts from residual statics, or replacement by statics calculated from refraction or tomography methods. These static shifts are inverted back to the multiple layer model to provide a revised model. This revised model forms a new 2D framework grid for additional 2D seismic lines. Where there are 3D surveys modeled with different methods of statics solutions, the framework provides primary control for cokriging of the statics solution from 3D surveys.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2011 SEG Annual Meeting, September 18–23, 2011

Paper Number: SEG-2011-4010

... contractor (top) using flexible binning as their path to increase S/N and continuity of reflections, while the second contractor (bottom) used regular binning and utilized cross-spreads and offset-vector tiling as well as iterative and continuous

**statics**and velocity**corrections**with signal processing in...
Abstract

ABSTRACT Seismic statics problem, in the case of a complex near surface, is seldom resolved on an early stage of sequential processing and is attempted to be compensated for with velocity manipulation, imaging techniques and cosmetic algorithms later in the processing flow. This approach often leads to the wrong representation of geology, erroneous velocity field and distorted interpretation. Accurately resolved statics at appropriate processing stage minimizes velocity errors, reduces overall processing cycle time and results in a more realistic seismic image, which translates into a more reliable and unambiguous interpretation. We have developed a continuous statics/velocity analysis based on the interactive statics technology, which allows for fast and reliable static time shifts and velocity decoupling.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2012-0016

... Building a multiple layer model for near-surface

**static****corrections**AbdulAziz Al-Saad*, Ralph Bridle, Saudi Aramco, Dhahran, Asad A. Ali and Mohammad Waseem Akhtar, BGP, Dhahran Summary The first 100 m of near-surface geology may be very complex and challenging to model for**static****corrections**. The...
Abstract

Summary The first 100 m of near-surface geology may be very complex and challenging to model for static corrections. The topography in arid environments includes sand dunes, outcrops, dry flash flood valleys ( wadis ) and salt flats ( sabkhas ). The near-surface base of weathering and the velocity of the unconsolidated material are highly variable. Below the unconsolidated weathering layer the rock strata often becomes more uniform and regular. The single layer velocity model (Buck, 1996), assumes that the base of weathering (low velocity material) is above the datum and that the upholes adequately sample and define the near-surface velocity field. Where there are shallow upholes the single layer velocity model may only model the weathering velocity not its thickness and ignores the higher velocity consolidated layer below the base of weathering. The uphole survey is a real physical data source for near-surface models. In Saudi Arabia, upholes of 100m nominal depth were usually acquired spaced 4 km along the 2D seismic acquisition line grid. The quality of the time/depth picks is variable because of inaccuracies in picking of the first arrival times and in the depth positioning of the geophone in the uphole. A multiple layer model is a comprehensive solution that will accommodate all position of the datum relative to the base of weathering. Having modeled the static corrections for the 2D seismic lines, a single effective layer velocity can be calculated. This single velocity would generate the same static, thus it is not a physical velocity. Where the datum is above surface and there are positive static corrections there will be negative single effective velocity.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2010-1897

... Summary Irregularities in thickness and velocity of near-surface layers may adversely affect seismic reflection images.

**Static****corrections**, calculated from near-surface velocity models, are used to remove the effects of the variable near surface. In this paper near-surface layers are...
Abstract

Summary Irregularities in thickness and velocity of near-surface layers may adversely affect seismic reflection images. Static corrections, calculated from near-surface velocity models, are used to remove the effects of the variable near surface. In this paper near-surface layers are characterized using a method known as Multi-Channel Analysis of Surface Waves (MASW). This method is mainly used for geotechnical engineering applications and is based on the dispersion properties of Rayleigh-waves. Here, it is used for calculating S-wave statics for a site located at Spring Coulee, Alberta. The results are compared to those generated by applying Generalized Linear Inversion (GLI) of first arrival times; a widely used and proven method for obtaining near-surface velocity and statics models for both P- and S-waves. In the Spring Coulee study area, the S-wave near-surface models, obtained by the GLI method, had different velocity layering and base of weathering depths than those derived from the P-waves. The MASW S-wave velocity model correlated well to the GLI S-wave model. For converted wave PS sections, the improvement in the quality of reflection events after applying the S-wave statics from the MASW model is similar to the event quality after application of the S-wave statics generated from the GLI model. Identifying and picking S-wave first arrivals manually is a difficult and time consuming process. Unfortunately, automatic picking programs do not generally work well for S-wave refractions. Confusing Swaves with Rayleigh-waves can also be a significant problem. Picking fundamental mode dispersion curves of Rayleigh-waves is an easy and fast way to derive S-wave velocities. Therefore, use of the MASW method is a potential alternative to the GLI method for modeling the Swave velocities in the near surface. Introduction Accurate knowledge of the near surface can be crucial, and use of this information can significantly improve the quality of seismic reflection images. For that reason, it is essential to understand and correctly analyse the nearsurface effects on the seismic wavefield. In January 2008, an extensive 2D multi-component seismic survey was acquired by the CREWES Project in Spring Coulee, Alberta. . The objective of the survey was to explore for potential hydrocarbons on a portion of land where the University of Calgary owned the mineral rights. The Spring Coulee survey area is located in southern Alberta west of the town of Magrath. The 2D-3C seismic line, used in this study, is indicated by the red line on the surface geology map shown in Figure 1. The surface geology at the site consists of Upper Cretaceous, St. Mary River Formation sandstones and shales. The seismic line is 6.54 km long and is oriented northeast to southwest.2 kgs of dynamite, buried at depth of 16 meters, was used for the shots. Receivers were single 3- component geophones. Receiver spacing was 10 meters, and the shot interval was 30 meters. The study dataset consists of 54 shots with 654 live receivers per shot. Theory In the case of an isotropic homogeneous half space, Rayleigh waves are non-dispersive with different frequencies traveling at the same velocity.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2007 SEG Annual Meeting, September 23–28, 2007

Paper Number: SEG-2007-2827

... calculation tomographic

**static****correction**method travel time convergence reservoir characterization tomographic inversion**static****correction**time difference parallel irregular grid tomographic**static****correction**grid velocity layer tomographic method near-surface velocity structure...
Abstract

ABSTRACT Based on conventional tomographic inversion methods, this paper presents a tomographic static correction with vertically parallel irregular grids. Our approach represents significant improvement in theory and application of tomographic inversion compared to conventional methods. Both synthetic and real data examples show excellent improvement in model convergence, which demonstrates the utility of this method.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

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

Paper Number: SEG-2010-1861

...Hybrid raypath interferometry:

**correcting**converted wave receiver**statics**David C. Henley* CREWES, Dept. of Geoscience, Univ. of Calgary Summary A technique termed hybrid raypath interferometry , for removing near-surface effects from seismic data, is used to remove converted wave receiver**statics**...
Abstract

Summary A technique termed ‘hybrid raypath interferometry’, for removing near-surface effects from seismic data, is used to remove converted wave receiver statics. A model study shows that artifacts caused by the ‘hybrid’ aspect of the method are minimized by a ‘conditioning’ step. Introduction In the most general sense, seismic interferometry includes acquisition and processing techniques which use crosscorrelations of raw traces to help image the data, or to remove various effects from the traces before imaging. A surge of interest in this broad field has led to a number of new techniques for passive seismic imaging (Draganov et al., 2009), migration (Zhou et al., 2006), and removal of near-surface effects, including statics (Bakulin and Calvert, 2006), (Henley, 2008), for example. Cross-correlations of raw seismic traces have been central to statics correction techniques for many years, typically being used to detect the relative time shift between two raw traces or between a raw trace and a ‘pilot’ trace. Until recently, however, only the lag times of the crosscorrelation maxima have been used in statics computations. We, however, use modified cross-correlation functions to derive inverse filters, which then deconvolve the static shifts and other phase differences from the raw traces, hence ‘statics deconvolution’ (Henley, 2006). Initially applied in the common-shot or common-receiver domain, statics deconvolution was later extended to the ‘common-raypath’ domain, which removed the constraints of surface-consistency and time-stationarity. This enabled the technique to solve difficult statics problems, like those encountered in the Arctic, with its irregular high-velocity surface permafrost layer. The first successful demonstration of ‘raypath interferometry’, in fact, was on a MacKenzie Delta seismic line with very large non-surface-consistent statics associated with river channels. The most successful variant of raypath interferometry utilized pilot traces created from raw seismic traces summed along structural horizons. Hence, the initial attempt to apply interferometry to converted wave data followed the same approach. The limited offset aperture and lower S/N of the PS traces, however, made it difficult to create useable pilot traces. DeMeersman and Roizman (2009), however, showed how to use cross-correlations of PP and PS direct arrival events to find receiver statics, using both vertical and radial seismic components, and we subsequently modified the raypath interferometry method to use PP events as pilot traces for PS events—hence ‘ hybrid raypath interferometry’. Theoretical concerns Conventionally, interferometry involves cross-correlations of similar traces containing directly corresponding events (like reflection sequences). When these events are aligned by the proper shift between traces, they all contribute to the correlation maximum. In hybrid interferometry, however, we compare traces which may share only one common event (a reflection on the PP trace and a conversion on the PS trace from the same geological horizon), and which contain other non-corresponding events. The common event chosen is usually stronger than neighboring events, on both traces, so the global cross-correlation maximum will usually indicate the relative shift between the reflection on the PP trace and the corresponding converted event on the PS trace.

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