Researchers Submit Patent Application, "Shear Noise Attenuation and Data Matching for Ocean Bottom Node Data Using Complex Wavelet Transforms", for Approval
The patent's assignee is Cggveritas Service Sa.
News editors obtained the following quote from the background information supplied by the inventors: "Seismic data acquisition and processing techniques are used to generate a profile (image) of a geophysical structure (subsurface) of the strata underlying the land surface or seafloor. Among other things, seismic data acquisition involves the generation of acoustic waves and the collection of reflected/refracted versions of those acoustic waves to generate the image. This image does not necessarily provide an accurate location for oil and gas reservoirs, but it may suggest, to those trained in the field, the presence or absence of oil and/or gas reservoirs. Thus, providing an improved image of the subsurface in a shorter period of time is an ongoing process in the field of seismic surveying.
"Considering the characteristics of ocean-bottom-node (OBN) data processing, pressure data (P), recorded by hydrophones and vertical particle velocity data (Vz), recorded by geophones are jointly processed for the separation of upward traveling and downward traveling wave fields. Based on the fact that upward traveling waves in P data and Vz data have the same polarity and downward traveling waves in P data and Vz data have opposite polarity, as shown in the equations:
"P=U+D and Vz=(k.sub.z/.rho..omega.)(U-D) (1)
"and described by
"A complicating factor associated with the above described wavefield separation derives from the fact that the Vz data usually contains shear wave noise that does not exist in the P component of the wave data, as described by J. Paffenholz,
"Continuing with the wavefield separation, shear wave noise attenuation in Vz and matching between P and Vz can be achieved in one step with local attribute matching in a dual-tree complex wavelet transform (DTCWT) domain as described by Z. Yu,
"Looking to how 2D DTCWT is implemented in a row-column separable way, as described by SELESNICK, i.e., analyzing filters are applied in rows and columns separately in analysis stages, wherein each analysis stage is equivalent to dividing the input F-K domain into the four sub-bands of HH band (high-f, high-k), HL band (high-f, low-k), LH band (low-f, high-k) and LL band (low-f, low-k). Continuing, the next analysis stage is recursively performed only within the LL band. Accordingly, in conventional 2D DTCWT the division of the input F-K domain is similar to FIG. 3(a) and this division pattern has an intrinsic problem, i.e., high-k components have poor frequency resolution in the low frequencies.
"Evaluating field seismic data indicates that shear wave noise in Vz usually exists in a large k range and in a low frequency range. Unfortunately, with the conventional 2D DTCWT band division, high-k shear noise cannot be adequately isolated in the frequency domain and therefore attenuation of high-k shear noise is inhibited. In another aspect, the drawbacks associated with the conventional 2D DTCWT are caused by the limit of angle resolving capability. In conventional 2D DTCWT, every stage has three wavelet bands, i.e, the LH band, the HH band and the HL band, and each band accommodates two 2D wavelet bases that are conjugate to each other. According to SELESNICK and YU, every stage accommodates exactly six orientations of the 2D wavelets. However, the limitation of six orientations restricts the angular resolving capability of the conventional 2D DTCWT, i.e., for high-f or high-k bands in the early analysis stages, the wavelet bases are sharp and should have a detailed angular resolving capability to resolve more than six orientations.
"Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "According to an embodiment, a method, stored in a memory and executing on a processor, for shear noise attenuation of seismic data in a High Angular Resolution Complex Wavelet Transformation (HARCWT) domain comprises computing a number of wavelet orientations for each stage of said HARCWT; performing a wavelet analysis in each frequency sub-band for all wave numbers and for all frequency sub-bands in each wave number; matching a vertical particle velocity data component to a pressure data component, based on said wavelet analysis, to suppress shear noise; and outputting shear noise suppressed seismic data based on said matching.
"According to another embodiment, a node for shear noise attenuation in a High Angular Resolution Complex Wavelet domain comprises one or more processors configured to execute computer instructions and a memory configured to store said computer instructions wherein said computer instructions further comprise: a wavelet orientation component for computing the number of wavelet orientations for each stage; a wavelet analysis component for removing said shear noise from associated seismic data; a matching component for matching a vertical particle velocity data component of said seismic data to a pressure data component of said seismic data; and an output component for outputting noise suppressed seismic data.
"According to another embodiment, a method, stored in a memory and executing on a processor, for shear noise attenuation of seismic data, includes computing a number of wavelet orientations for each stage of a transform, performing a wavelet analysis for each of the wavelet orientations, matching a vertical particle velocity data component to a pressure data component, based on said wavelet analysis, to suppress shear noise, and outputting shear noise suppressed seismic data.
BRIEF DESCRIPTION OF THE DRAWINGS
"The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
"FIGS. 1 and 2 show various aspects of an exemplary marine seismic survey system in which various shear noise suppression embodiments can be implemented;
"FIGS. 3a-d show various aspects of stage analysis associated with the embodiments;
"FIGS. 4a-e show various aspects of shot gather and P/Vz matching;
"FIG. 5 is a flowchart depicting a method of shear noise suppression according to an embodiment;
"FIGS. 6-7 shows various aspects of software components or modules which can be used to implement the embodiments; and
"FIG. 8 illustrates an exemplary data processing device or system which can be used to implement the embodiments."
For additional information on this patent application, see: PENG, Can; HUANG, Rongxin; ASMEROM, Biniam. Shear Noise Attenuation and Data Matching for Ocean Bottom Node Data Using Complex Wavelet Transforms. Filed
Keywords for this news article include: Cggveritas Service Sa, Information Technology, Information and Data Processing.
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