Wang, Xin; Schuster, Gerard T.(SEG Technical Program Expanded Abstracts 2012, Society of Exploration Geophysicists, 2012-10-25)[Conference Paper]
Kirchhoff based multi-source least-squares migration (MSLSM) is applied to marine streamer data. To suppress the crosstalk noise from the excitation of multiple sources, a dynamic encoding function (including both time-shifts and polarity changes) is applied to the receiver side traces. Results show that the MSLSM images are of better quality than the standard Kirchhoff migration and reverse time migration images; moreover, the migration artifacts are reduced and image resolution is significantly improved. The computational cost of MSLSM is about the same as conventional least-squares migration, but its IO cost is significantly decreased.
Dai, Wei; Boonyasiriwat, Chaiwoot; Schuster, Gerard T.(SEG Technical Program Expanded Abstracts 2010, Society of Exploration Geophysicists, 2012-03-22)[Conference Paper]
We present the theory and numerical results for least-squares reverse time migration (LSRTM) of phase-encoded supergathers, where each supergather is the superposition of phased-encoded shots. Three type of encoding functions are used in this study: random time shift, random source polarity and random source location selected from a pre-designed table. Numerical tests for the 3D SEG/EAGE Overthrust model show that multi-source LSRTM can suppress migration artifacts in the migration image and remove most of the crosstalk noise from multi-source data. Empirical results suggest that multi-source LSRTM can provide a noticeable increase in computational efficiency compared to standard RTM, when the CSGs in a supergather are modeled and migrated together with a finite-difference simulator. If the phase-encoding functions are dynamically changed after each iteration of LSRTM, the best images are obtained. The potential drawback is that the final results are very sensitive to the accuracy of the starting model.
Fei, Tong W.; Luo, Yi; Schuster, Gerard T.(SEG Technical Program Expanded Abstracts 2010, Society of Exploration Geophysicists, 2012-03-22)[Conference Paper]
Reverse-time migration (RTM), based on the full two-way wave equation, has gained interest and become a popular imaging tool for complex structures in the last few years. The method is well-known for its ability to better image the steeply dipping and overturned structures than the migration methods based on the one-way wave equation extrapolation. However, the RTM image often contains low frequency and back-scattering noise, and the imaging quality is sensitive to the migration velocity. In order to improve the RTM imaging quality and make the RTM image less sensitive to the velocity model, we developed an RTM de-blending technique which separates upgoing and downgoing source and receiver wavefields, and then use them to construct final RTM images. Test results show that decomposed images obtained from only the downgoing source and receiver wavefields are less sensitive to velocity. It removes unwanted noise and migration artifacts from conventional RTM, and the imaging quality is greatly improved compared with a conventional RTM image.
Hanafy, Sherif M.; Sandoval Curiel, Ernesto(SEG Technical Program Expanded Abstracts 2010, Society of Exploration Geophysicists, 2012-03-22)[Conference Paper]
We present the theory and one field example of using seismic waves to send and receive coded messages. The method requires the recording of one calibration shot gather that will be used to decode the message. Coded messages can be send with a system similar to Baudot code. One field test is recorded in Tucson, AZ., USA, where we send and received 3-short messages. One possible application of this method is to send coded messages from trapped miners to the surface. Advantages of this method are; no velocity model is required, easy and fast to use.
Schuster, Gerard T.; Huang, Yunsong(SEG Technical Program Expanded Abstracts 2014, Society of Exploration Geophysicists, 2014-08-05)[Conference Paper]
We show that superresolution imaging in the far-field region of the sources and receivers is theoretically possible if migration of resonant multiples is employed. A resonant multiple is one that bounces back and forth between two scattering points or two neighboring reflectors. For a source with frequency f, N roundtrips in propagating between two scatterers increases the effective frequency to 2N× f and decreases the effective wavelength λ to λ/2N. Thus, interbed multiples can, in principle, be used as high-frequency probes to estimate detailed properties of layers. This is not only applicable to crustal reflections, but also to mantle and core reverberations of interest to earthquake seismologists.
Guo, Qiang; Alkhalifah, Tariq Ali(SEG Technical Program Expanded Abstracts 2018, Society of Exploration Geophysicists, 2018-08-27)[Conference Paper]
Finding a velocity model that produces simulated data that fits the observed one is the main objective of full waveform inversion (FWI). To meet such an objective we often need to solve for a high-resolution delineation of the subsurface medium. The current algorithms are usually implemented over the entire model space with a consistent discretization and physical assumptions, which can be both complex and costly in practice. Alternatively, we develop an FWI framework that utilizes a split model to an overburden, like the medium above a reservoir, and the underlying represented by data at a datum at the bottom of the overburden. We simultaneously invert for the velocity model above the datum level, which effects the redatuming process but often owns to more simple physics, and the corresponding data at that datum, which may represent a complex reservoir region. We formulate the redatuming operator using a modified expression of the extended Born representation, which is a multi-dimensional crosscorrelation. The resulting modeling needed in such an inversion includes wavefields from a source and those ignited at the datum level. We estimate the overburden velocity using low-wavenumber updates along the modeled reflection wavepaths. The dimensionality of the model extension and the retrieved data helps us match data on the surface, which results in a robust implementation. Tests on a simple model and the Marmousi show that our method can build a good velocity model and also obtain redatumed data with reasonable amplitude accuracy.
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