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Collaborating Authors
Cary, Peter
- North America > United States > Texas (0.22)
- North America > Canada > Alberta (0.18)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.34)
Characterizing a Cardium waterflood via 3-Cโ3D land surface seismic: The Washout Creek experience
Perz, Michael (TGS) | Chopra, Satinder (TGS) | Sharma, Ritesh (TGS) | Cary, Peter (TGS) | Li, Xinxiang (Arcis Seismic Solutions) | Ohlhauser, Wendy (Arcis Seismic Solutions) | Pike, Kimberly (PennWest) | Creaser, Brian (Enerplus) | Nemati, M. Hossein (Arcis)
ABSTRACT A high-effort, multicomponent 3C3D seismic data set was acquired over a mature oil field in central Alberta in order to better understand the characteristics of a waterflood operation. True-amplitude processing of the data was undertaken, and joint PP-PS prestack impedance inversion reveals a pronounced set of anomalous low-impedance lineaments at the target level which exhibit a very strong spatial correlation with known water injector locations. Rock physics modeling demonstrates that fluid pressure effects are heavily influencing the seismic response in the vicinity of the injectors, and are accounting for the observed low-impedance anomalies. Analysis of injection and production data suggests that the seismic data can play a vital role in identifying zones of unswept pay in this area. Presentation Date: Monday, October 17, 2016 Start Time: 1:00:00 PM Location: 156 Presentation Type: ORAL
- Europe (0.33)
- North America > Canada > Alberta (0.25)
- Geology > Geological Subdiscipline > Geomechanics (0.72)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.31)
- North America > Canada > Alberta > Western Canada Sedimentary Basin > Alberta Basin > Deep Basin > Cardium Formation (0.99)
- Europe > Denmark > North Sea > Danish Sector > Central Graben > Block 5505/13 > Halfdan Field > Maastrichtian Formation (0.99)
- Europe > Denmark > North Sea > Danish Sector > Central Graben > Block 5505/13 > Halfdan Field > Danian Formation (0.99)
- (2 more...)
ABSTRACT In 2015 a time-lapse buried receiver 3C/2D seismic experiment was performed in the heavy oil area of NE Alberta, Canada. The purpose was to determine if on-going reservoir monitoring was feasible beneath a thick layer of muskeg. 3C analog geophones and digital sensors were installed at surface, 3m and 9m along with dynamite sources at 9m. Shot points were doubled at each source location in order to acquire data during winter conditions and also during the following summer. The test was in response to poorly imaged seismic stacks and inversions from previously acquired 3C/3D surface seismic data. High quality time-lapse PP and PS images were produced from the 2D data when both the dynamite sources and receivers were buried to 9m depths. Recording PP and PS reflections that bypass the absorptive near-surface muskeg layer with buried receivers and sources facilitates time-lapse multicomponent seismic monitoring in this area. Presentation Date: Tuesday, October 18, 2016 Start Time: 8:50:00 AM Location: 163/165 Presentation Type: ORAL
Summary Surface-consistent scaling is used in land AVO-compliant processing flows to remove shot-to-shot and receiver-to-receiver amplitude variations. In conventional surface-consistent scaling methods, the scalars are obtained by decomposing the RMS amplitudes of prestack traces that are always contaminated to some extent by noise. The RMS amplitudes are a measure of the total energy on a trace (signal + noise) rather than just signal. Consequently, if noise increases in one area of a survey, the signal in that area is not scaled up enough (the noise biases the scalars). Despite attempts to remove the effects of noise on the derived scalars with various noise attenuation methods, we have observed that data often are poorly scaled at the end of a typical AVO-compliant run stream. As a solution to this problem, Cary and Nagarajappa (2013) proposed an unbiased scaling approach in which the shot and receiver consistent signal estimates were obtained from the RMS amplitudes of the shot and receiver stacks. A restriction of this method is that the data in the analysis window must be nearly flat in order to stack in the shot or receiver domain and obtain accurate scalar estimates. When the data is not flat, then it first needs to be flattened, which can be difficult when geology is complicated. In this paper, we propose an unbiased scaling method that avoids the use of shot and receiver stacks. The proposed method computes the prestack amplitudes from the zero-lag value of the crosscorrelations between each prestack trace and its CDP stack trace. Such a crosscorrelation can provide unbiased prestack amplitudes. In addition, the prestack amplitudes are not dependent on the time variations in the structure. The shot and receiver-consistent averages can then be computed to obtain the scalars in a surface-consistent manner. Introduction In land data, causes of amplitude variations between shots and between receivers include near-surface weathering conditions, coupling, and source/receiver type differences. Surface-consistent scaling is routinely used to estimate and remove these variations. Surface-consistent scaling methods and their applications are discussed in Taner & Koehler (1981), Taner et al. (1991), Yu et al. (1985) and Garceran et al. (2013). In these methods, the RMS amplitudes of the prestack traces are used and a set of equations are formed. The equations are then solved to obtain the surface-consistent scalar estimates. These scalar estimates can do a poor job of balancing the signal in the data because the RMS amplitudes of the prestack traces are biased by spatially-variant noise. Cary and Nagarajappa (2013) showed that unbiased surface-consistent scalar estimates could be obtained by computing the RMS amplitudes of the shot stacks and of the receiver stacks. It was shown that these stack amplitudes are unbiased estimates of the shot and receiver-consistent amplitude variations of the signal in the data. Henceforth in this paper, we refer to this approach as the unbiased scaling method.
Summary In land AVO processing, near-surface heterogeneity issues are resolved through the use of surface-consistent processing. In particular, it is assumed that variable source and receiver wavelet and coupling effects are corrected by surface-consistent deconvolution. Statics solutions are then resolved assuming that surface-consistent phase variations no longer exist. However, surface-consistent wavelet phase errors may still exist in the data after deconvolution due to factors such as surface-consistent noise. If this is true, the phase errors would be difficult to observe because surface-consistent statics would attempt to "resolve" the wavelet misalignments caused by phase variations with statics corrections. We have developed a robust surface-consistent method that simultaneously resolves residual statics and phase rotations by maximizing the stack power. In our solutions we observe that statics and phase estimates are strongly anticorrelated, which is what one would expect if statics were being used to correct phase errors earlier in the processing flow. In addition, phase errors estimated by the method often correlate with features of surface topography and with different source types, which adds to the evidence that residual phase errors are being correctly resolved.
Summary A new approximate migration weight is developed for Kirchhoff migration of converted-wave data. As with previous approximations it is based on the exact weight for a homogeneous medium. However, rather than assuming equality of travel path distances from source to image point and image point to receiver, it assumes that the total traveltime is partitioned in a way that is consistent with common-conversion point reflection. It is shown that, through solution of a cubic equation, this results in an efficient approach with no evaluations within the inner migration loop. Application of this new migration weight in prestack time migration of typical multicomponent land data shows that it yields migrated stacks and gathers very similar to those obtained using the exact homogeneous migration weight, and superior to those obtained using migration weights borrowed from P-wave migration theory, particularly in the near-surface region.
Summary Surface-consistent scaling has been a standard step in the processing of land seismic data for many years, especially in the preparation of pre-stack data for AVO analysis and inversion. Despite the fact that this type of process is in such common use, we believe that there is a basic problem with how the surface-consistent scaling equations are normally solved that results in scalars that are biased by variable levels of random noise in the data. Instead of scaling the energy of the signal in a surface-consistent manner, the normal scaling algorithm scales the energy of the signal plus random noise in a surface-consistent manner. In this abstract we begin by showing evidence of incorrect amplitude scaling of the seismic signal on a real data example after the normal surface-consistent scaling process has been applied. An explanation for the poor scaling is then proposed with the aid of synthetic data that includes both surface-consistent signal and surface-consistent noise. Finally, a simple unbiased method for solving the surface-consistent scaling equations is proposed.
Summary In land multi-component (MC) data processing, the orientation of each receiver's horizontal components in the field (H1 and H2) is seldom known accurately. Methods to derive the orientations from recorded data are in common use. They work by assuming a homogeneous, isotropic near-surface earth model and derive an orientation using P-wave first arrival amplitudes on the horizontal components. These methods are known to work well on marine OBC/OBN data and down-hole VSP data. For land data, the near-surface is often strongly inhomogeneous and anisotropic. The P-wave first-break methods can therefore yield inaccurate results. We show examples that illustrate the deviation of P-wave first-break amplitudes from what is expected from a homogeneous near-surface earth.
Motivated by the desire for greater resolution in PS data, and an interest in methods designed to produce this, we have explored some fundamental concepts of PS resolution in order to better understand proposed methods. Our study has produced three key results: PS-to-PP mapping using either interval or average velocity ratios yields identical results. Although mapping changes the bandwidth of the PS signal, it does not change its wavelength or resolution. Modest increases in resolution can be realized after mapping if the wavelet is known, but any method designed to increase bandwidth without such knowledge should be treated with caution.
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Pennsylvania > Appalachian Basin > Marcellus Shale Formation (0.99)
- (3 more...)
Summary Two methods have recently been published for carrying out nonstationary spectral broadening (and narrowing) of PS data after it has been mapped into the PP time domain. We present a study which investigates these two papers by Bansal & Matheney (2010) and by Gaiser (2011) (see also Gaiser et al., 2011a,b). The two approaches differ in purpose, in method of PS-to-PP time mapping, in proposed spectral corrections, and in methods for applying those corrections. In the context of comparing these two studies we add some clarification of fundamental resolution issues and illustrate our points with simple synthetic seismograms.
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Pennsylvania > Appalachian Basin > Marcellus Shale Formation (0.99)
- (3 more...)