The effect of noise generated by previous shots on seismic reflection data

Geophysics ◽  
2008 ◽  
Vol 73 (3) ◽  
pp. Q9-Q17 ◽  
Author(s):  
Martin Landrø
Keyword(s):  
Signal To Noise Ratio ◽  
Time Lapse ◽  
Time Interval ◽  
Source Strength ◽  
Recording Time ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Seismic Acquisition ◽  
Marine Seismic ◽  
Signal Time

In marine seismic acquisition, the typical time interval between two adjacent shots is about [Formula: see text]. This interval is considered sufficient to avoid the signal from one shot interfering with the signal from the next shot. However, when we are looking for very weak signals or weak changes in a given signal (time-lapse seismic), the influence of the shot-generated noise can be of importance. In the present work, shot records with a recording time of [Formula: see text] are used to analyze the influence of the shot-generated noise from the previous shot. Simple decay models are used to match the observed rms decay curves. These calibrated models are used to estimate variations in signal-to-noise ratio versus shot time interval and source strength. For instance, if the source strength is doubled and the time interval between two shots is increased from [Formula: see text], an improvement in the signal-to-shot-generated noise from the previous shot of [Formula: see text] is expected. Especially for time-lapse seismic using permanently installed receivers, this way of increasing the S/N might be useful.

scholarly journals Time-lapse imaging using 3D ultra-high-frequency marine seismic reflection data

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. P13-P25
Author(s):  
Michael J. Faggetter ◽  
Mark E. Vardy ◽  
Justin K. Dix ◽  
Jonathan M. Bull ◽  
Timothy J. Henstock
Keyword(s):  
High Frequency ◽  
Seismic Reflection ◽  
High Tide ◽  
Time Lapse ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Ultra High Frequency ◽  
Reflection Data ◽  
Marine Seismic

Time-lapse (4D) seismic imaging is now widely used as a tool to map and interpret changes in deep reservoirs as well as investigate dynamic, shallow hydrological processes in the near surface. However, there are very few examples of time-lapse analysis using ultra-high-frequency (UHF; kHz range) marine seismic reflection data. Exacting requirements for navigation can be prohibitive for acquiring coherent, true-3D volumes. Variable environmental noise can also lead to poor amplitude repeatability and make it difficult to identify differences that are related to real physical changes. Overcoming these challenges opens up a range of potential applications for monitoring the subsurface at decimetric resolution, including geohazards, geologic structures, as well as the bed-level and subsurface response to anthropogenic activities. Navigation postprocessing was incorporated to improve the acquisition and processing workflow for the 3D Chirp subbottom profiler and provide stable, centimeter-level absolute positioning, resulting in well-matched 3D data and mitigating 4D noise for data stacked into [Formula: see text] common-midpoint bins. Within an example 4D data set acquired on the south coast of the UK, interpretable differences are recorded within a shallow gas blanket. Reflections from the top and bottom of a gas pocket are imaged at low tide, whereas at high tide only the upper reflection is imaged. This case study demonstrates the viability of time-lapse UHF 3D seismic reflection for quantitative mapping of decimeter-scale changes within the shallow marine subsurface.

Least-squares data-to-data migration: An approach for migrating free-surface-related multiples

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. S83-S94 ◽  
Author(s):  
Yikang Zheng ◽  
Yibo Wang ◽  
Xu Chang
Keyword(s):  
Free Surface ◽  
Least Squares ◽  
Seismic Data ◽  
Signal To Noise Ratio ◽  
Data Migration ◽  
Subsurface Imaging ◽  
Full Data ◽  
Recording Time ◽  
Numerical Tests ◽  
Marine Seismic

Free-surface-related multiples can provide extra illumination of the subsurface and thus can be usefully included in migration procedures. However, most multiple migration approaches require separation of primaries and free-surface-related multiples or at least prediction of multiples in advance, which is time consuming and prone to errors. The data-to-data migration (DDM) method migrates free-surface-related multiples by forward and backward propagating the recorded full data (containing primaries and free-surface-related multiples). For DDM, there is no need to predict or separate multiples, but the migration results suffer from the crosstalk generated by crosscorrelations of undesired seismic events, e.g., primaries and second-order free-surface-related multiples. We have developed least-squares DDM (LSDDM) for marine data to eliminate the crosstalk generated by DDM. In each iteration, the forward-propagated primaries and free-surface-related multiples are crosscorrelated with the backward-propagated primary and free-surface-related multiple residuals to form the reflectivity gradient. We use a three-layer model and the Marmousi model for numerical tests. The results validate that LSDDM can provide a migrated image with higher signal-to-noise ratio and more balanced amplitudes than DDM. The LSDDM approach might be valuable for general subsurface imaging for marine seismic data when the migration velocity is accurate, and the acquired data have sufficient recording time.

EXTENDED ARRAYS FOR MARINE SEISMIC ACQUISITION

Geophysics ◽  
1978 ◽  
Vol 43 (1) ◽  
pp. 3-22 ◽  
Author(s):  
J. H. Lofthouse ◽  
G. T. Bennett
Keyword(s):  
Data Quality ◽  
Data Acquisition ◽  
Signal Amplitude ◽  
Eastern Canada ◽  
Seismic Reflection Data ◽  
The North ◽  
Reflection Data ◽  
Formed Part ◽  
Marine Seismic ◽  
Receiver Arrays

In‐line arrays for both source and receiver have been implemented for marine seismic reflection data acquisition. The in‐line array dimensions (variable within limits) are considerably greater than any previously used system of which we are aware. The arrays were designed to attenuate extremely strong sea‐bottom multiples during the data acquisition phase. The source comprised 25 airguns arranged in five identical in‐line subarrays. Each subarray produced a signal of better than 6 barmeters acoustic intensity with a primary‐to‐bubble ratio of approximately 4.4 from guns totaling 297 cu in. When this source was delivered in 1973, it constituted the most powerful production airgun source for which we had seen calibration measurements. Receiver arrays were implemented by a “weighting‐mixing” box (which formed part of the DFS IV instrument), the input to which comprised 53 channels of data each from a 50 m live section in the streamer cable. Processing techniques which are complementary to the field procedures have been developed. Comparisons with “conventional” data (and such data processed to simulate field arrays) show significant improvements in “data quality” from the new field techniques, that is, the new data are easier to interpret geologically because interfering multiples have been attenuated relative to desired energy. Whilst the large outgoing signal amplitude will have made some contribution to the data quality, the major improvement is believed to result from the use of arrays in the recording phase. This system, first used for production in August 1973, was subsequently used successfully during recording of 17,000 km of offshore seismic data from Eastern Canada, the North Sea, and the Mediterranean.

Labeling long‐period multiple reflections

Geophysics ◽  
1989 ◽  
Vol 54 (1) ◽  
pp. 122-126 ◽  
Author(s):  
R. J. J. Hardy ◽  
M. R. Warner ◽  
R. W. Hobbs
Keyword(s):  
Seismic Reflection ◽  
High Amplitude ◽  
Data Sets ◽  
Multiple Reflections ◽  
Multiple Series ◽  
Seismic Reflection Data ◽  
Long Period ◽  
Reflection Data ◽  
Zero Offset ◽  
Marine Seismic

The many techniques that have been developed to remove multiple reflections from seismic data all leave remnant energy which can cause ambiguity in interpretation. The removal methods are mostly based on periodicity (e.g., Sinton et al., 1978) or the moveout difference between primary and multiple events (e.g., Schneider et al., 1965). They work on synthetic and selected field data sets but are rather unsatisfactory when applied to high‐amplitude, long‐period multiples in marine seismic reflection data acquired in moderately deep (700 m to 3 km) water. Differential moveout is often better than periodicity at discriminating between types of events because, while a multiple series may look periodic to the eye, it is only exactly so on zero‐offset reflections from horizontal layers. The technique of seismic event labeling described below works by returning offset information from CDP gathers to a stacked section by color coding, thereby discriminating between seismic reflection events by differential normal moveout. Events appear as a superposition of colors; the direction of color fringes indicates whether an event has been overcorrected or undercorrected for its hyperbolic normal moveout.

scholarly journals Seismic interferometry using multidimensional deconvolution and crosscorrelation for crosswell seismic reflection data without borehole sources

Geophysics ◽  
2011 ◽  
Vol 76 (1) ◽  
pp. SA19-SA34 ◽  
Author(s):  
Shohei Minato ◽  
Toshifumi Matsuoka ◽  
Takeshi Tsuji ◽  
Deyan Draganov ◽  
Jürg Hunziker ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Field Data ◽  
Time Lapse ◽  
P Wave ◽  
Source Distribution ◽  
Seismic Interferometry ◽  
Imaging Method ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Receiver Arrays

Crosswell reflection method is a high-resolution seismic imaging method that uses recordings between boreholes. The need for downhole sources is a restrictive factor in its application, for example, to time-lapse surveys. An alternative is to use surface sources in combination with seismic interferometry. Seismic interferometry (SI) could retrieve the reflection response at one of the boreholes as if from a source inside the other borehole. We investigate the applicability of SI for the retrieval of the reflection response between two boreholes using numerically modeled field data. We compare two SI approaches — crosscorrelation (CC) and multidimensional deconvolution (MDD). SI by MDD is less sensitive to underillumination from the source distribution, but requires inversion of the recordings at one of the receiver arrays from all the available sources. We find that the inversion problem is ill-posed, and propose to stabilize it using singular-value decomposition. The results show that the reflections from deep boundaries are retrieved very well using both the CC and MDD methods. Furthermore, the MDD results exhibit more realistic amplitudes than those from the CC method for downgoing reflections from shallow boundaries. We find that the results retrieved from the application of both methods to field data agree well with crosswell seismic-reflection data using borehole sources and with the logged P-wave velocity.

Application of 3D seismic techniques to evaluate ore resources in the West Wits Line goldfield and portions of the West Rand goldfield, South Africa

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC163-WC171 ◽  
Author(s):  
Musa S. D. Manzi ◽  
Mark A. S. Gibson ◽  
Kim A. A. Hein ◽  
Nick King ◽  
Raymond J. Durrheim
Keyword(s):  
Seismic Reflection ◽  
Signal To Noise Ratio ◽  
Mine Planning ◽  
3D Seismic ◽  
Borehole Data ◽  
The West ◽  
Seismic Reflection Data ◽  
Witwatersrand Basin ◽  
Reflection Data ◽  
Time Migration

As expensive as 3D seismic reflection surveys are, their high cost is justified by improved imaging of certain ore horizons in some of the Witwatersrand basin gold mines. The merged historical 3D seismic reflection data acquired for Kloof and South Deep mines forms an integral part of their Ventersdorp Contact Reef mine planning and development programme. The recent advances in 3D seismic technology have motivated the reprocessing and reinterpretation of the old data sets using the latest algorithms, therefore significantly increasing the signal-to-noise ratio of the data. In particular, the prestack time migration technique has provided better stratigraphic and structural imaging in complex faulted areas, such as the Witwatersrand basin, relative to older poststack migration methods. Interpretation tools such as seismic attributes have been used to identify a number of subtle geologic structures that have direct impact on ore resource evaluation. Other improvements include more accurate mapping of the depths, dip, and strike of the key seismic horizons and auriferous reefs, yielding a better understanding of the interrelationship between fault activity and reef distribution, and the relative chronology of tectonic events. The 3D seismic data, when integrated with underground mapping and borehole data, provide better imaging and modeling of critical major fault systems and zones of reef loss. Many faults resolve as multifault segments that bound unmined blocks leading to the discovery and delineation of resources in faulted areas of the mines.

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