Adaptive seismic noise and interference attenuation method

#This invention relates to seismic data acquisition and to methods of processing seismic data. It relates to a process for filtering coherent noise and interference from seismic data by an adaptive beamforming method. In another aspect, it relates to adaptively filtering coherent noise and interference from seismic data while preserving seismic signals with arbitrary spectral content in the frequency-wavenumber domain. In yet another aspect, it relates to adaptively filtering coherent noise and interference that is temporally and spatially nonstationary. In a further aspect, it relates to adaptively filtering coherent noise and interference that has been recorded by a sensor array in the presence of perturbations.

#In seismic surveys, a seismic source induces seismic waves at or near the surface of the earth. Explosives, vibrating devices and airguns are examples of seismic sources. These waves propagate through the earth and are reflected, refracted, and diffracted by formations within the earth, and can be detected by a plurality of sensors (typically geophones or hydrophones) at the earth's surface. Each such receiver monitors the seismic wavefield, which is then recorded. The data received by a receiver and then recorded are collectively called a trace. The collection of traces are stored for further processing to gain information about the earth's subsurface. Such information is commonly interpreted to detect the possible presence of hydrocarbons, or to monitor changes in hydrocarbon bearing rocks.

#Seismic data in general contains coherent noise signals, along with seismic reflection signals. These noise signals, hereafter referred to as the noise, interfere with the interpretation of the seismic signals, and degrade the quality of the subsurface images that can be obtained by further processing. It is therefore desirable to suppress the noise that is present in the recorded data before processing it for imaging.

#FIG. 1 illustrates general elements of a seismic land acquisition;

#FIG. 2 shows a general block diagram of an adaptive beamformer in accordance an example of the present invention;

#FIG. 3 shows the example of a region preserved by an adaptive beamformer in accordance with an example of the present invention;

#In the following the basic concepts underlying the invention are developed in detail.

#A typical land seismic acquisition is illustrated in FIG. 1.

#A source 10 is activated, thus generating seismic waves 11, i.e acoustic waves with frequencies of less than 500 Hz. The waves travel though the interior of the Earth 12 and are reflected at various locations. Even though only one reflector 13 is shown, typically there are many reflectors, each reflecting a fraction of the seismic wave back to the surface. At the surface, seismic waves are recorded by seismic sensors 14 (geophones). These sensors are spread along a line or in a two-dimensional pattern.