Diffraction Enhancement Through Pre-Image Processing: Applications to Field Data, Sarawak Basin, East Malaysia

Abstract

The future exploration plans of the industry is to find a small-scale reservoir for possible economic hydrocarbon reserves. These reserves could be illuminated by the super-resolution of full seismic data, including fractured zones, pinch-outs, channel edges, small-scale faults, reflector unconformities, salt flanks, karst, caves and fluid fronts, which are generally known as small scattering objects. However, an imaging approach that includes the diffraction event individually and images it constitutes a new approach for the industry; it is known as diffraction imaging. This paper documents results of a seismic processing procedure conducted to enhance diffractions in Sarawak Basin, using datasets from the Malaysian Basin to which no diffraction processing has been applied. We observed that the diffraction amplitude achieves maximum value when the detector is positioned vertically above the end point of the reflector, but drops off with increasing offset-distance from the point. Furthermore, the rate of attenuation of the diffracted wave energy is greater than that of the normal reflected wave energy in the same medium. In addition, the results indicate that the near offset and far angle stack data provide better diffraction events. In the other hand far offset and near angle stack provides the poor diffraction response. These results were revealed by angle-stacking of near-, mid-, and far-offsets data (4.5, 22.5 and 31.5 degrees) that was conducted to study amplitude and phase change of the diffraction curve. The final imaged data provides better faults definition in the carbonate field data.

Inspiration for Seismic Diffraction Modelling, Separation, and Velocity in Depth Imaging

“…After using a Fourier transform to convert our data from the time domain into the frequency domain, the F-K (frequency-wavenumber) spectrum shows the amplitude distribution with the wavenumber. Through minimizing the forecast for outstanding work, many iteration tasks were performed whilst developing the local slope filter for separation of specular reflection from the full-wave seismic behavior, which is based on equivalent impression and prediction error filters [5,29]. The separation of reflection and diffraction energy is accurate, as this method accommodates wave responses from small subsurface discontinuities, such as faults, fractures, karst sections, and unconformities, which appear as diffraction in the data.…”

“…Further, these diffraction data are also used for travel time approximation for anisotropic imaging [3]. The separation of diffraction is widely used [4][5][6][7] for enhancement of seismic imaging, such as fault, fracture, complex variable velocity structure, and karstification imaging [8]. Further, the diffraction response for a nonzero separation of the source and receiver was presented by Berryhill in 1977 [9], in which theoretical support was obtained for applying the zero-separation theory to stack the seismic data.…”

“…The fractured basement can be seen at a depth of 2-5 km and varies with lateral extension. (c) North-west to south-east section [5].…”