1.2 Sarawak basin

Diffraction imaging analyzes were carried out in the Sarawak Basin, located north-west of Borneo, forming the southern boundary of the Oligocene-Recent Basin of the South China Sea; its tectonic evolution has been almost matched by seabed rifting and spread in the marginal basin of the South China Sea [4]. The majority of the Sarawak Basin, including this part of Malaysia, is composed of carbonates, making seismic imagery difficult. The pre-carbonated Oligocene deposit in the lower Miocene and later the terrestrial deposit filled the shelter zone in Cycle I and Cycle II. The cycles are described as follows: Cycles I and II (Upper Eocene to Lower Miocene) have been interpreted as channel sands, lowered clays, and deposited coal. Cycle III (lower-middle Miocene) contains fine limestone shale and sandstone, cycle IV (middle Miocene) is composed of limestone with few mixed clastics, cycle V (middle to upper Miocene) is recognized as limestone, cycle Advance Wave Modeling and Diffractions for High-Resolution Subsurface Seismic Imaging DOI: http://dx.doi.org/10.5772/intechopen.81164

VI to cycle VIII (upper Miocene to Pleistocene) is composed of open marine and coastal clays and sand, respectively. The progradante sediments from cycle V1 to cycle VIII have gradually stifled the large accumulations of carbonates to the present day. In the center of Luconia, carbonate deposits began at the beginning of the Miocene (cycle III) and increased significantly in the middle and late Miocene cycles IV and V [3]. The structure is dominated by a simple extension phase NS trend faults. These faults affected the deposits during cycles I and II and served as foci for the development of carbonate reefs of cycle IV and V and their accumulation. The dominance of intensive pre-carbonation structuring has therefore resulted in poor seismic image quality.

## 1.3 Diffraction

Diffraction hyperbolic patterns occur frequently in recorded seismic data, particularly in carbonate reservoirs due to abrupt lateral changes in impedance contrast and discontinuity of subterranean layers. However, a very serious doubt to the application of classical theory has claimed that stacked seismic data is not true zero separation data because it is not clear that the results of the stacking of data recorded on a wide range of source-receiver separations is practically close to the results of real zero separation recording, since diffraction amplitudes are concerned [5]. Berryhill also explained the concept and compared the theory of zero separation with source-geophone distance without zero separation, concluding that the diffraction amplitudes at a source-receiver separation different from zero and well known with respect to the wave and geometric propagation paths, a point diffractor gives rise to a hyperbolic diagram on the stacked section. Hyperbola is explained as a symmetrical open curve formed by the intersection of a circular cone with a plane at a smaller angle with its axis than the sides of the cone. Diffraction only be considered as hyperbolic if the recovery is homogeneous, which not a very natural supposition to make is. The curvature of the diffraction hyperbola depends on the speed of the medium, the apex being an indicator of the location of the defect. Diffraction imaging is a dare in seismic processing and adopted by a workflow by means of the common reflection surface by [6–8].

In reflection seismology applied to exploration geophysics, such wave propagation phenomena are employed to estimate the properties of the Earth's subsurface reflector. Furthermore, the diffraction phenomenon is also concerned with reflection because of the properties of the subsurface as defined above. The acoustic (seismic) impedance, Z=, Where V is the seismic wave velocity and ρ is density. Although seismic migration is now the one of the primary imaging tools employed in the field, the earliest analogue seismic records took the form of simple single-fold illustration [4, 9–12]. These recordings were characterized by diffracted energy and random noise, but they nonetheless provided a useful interpretation of the subsoil of the Earth. Later, mechanical migration eliminated the structural deformation of early seismic data, with CMP stacks condensing the amount of random noise as the diffracted energy is preserved. Seismic reflection and diffraction waves are essentially different physical phenomena. Most seismic processors tune and image by improving the seismic reflection data, and do not deliberate the diffracted waves present in the processed data, which carry most of the information regarding minor but important subsurface events [13]. Such small-scale underground events (such as faults, fractures, channels, karsts, and salty body edges) occur as diffracted waves in the seismic data, which can be captured [14, 15].

The plane wave destruction filter (PWD) was originally introduced by Claerbout [28] for the characterization of seismic images using the superposition of local plane waves. This PWD filter was based on the plane wave differential

equation, after the original plane wave destruction filter with the same approximation proved poor when applied to spatial folding data [16]. On the other hand, the dip frequency filtering approach is applied in the f-k domain. Here we use the Fourier transform to convert time data to the frequency domain, with a filter designed to eliminate reflections based on wave cycles per kilometer. In this paper, we develop a workflow that captures these events on a small scale through separate diffractions based on the regularity and continuity of the slope of the local event that corresponds to the reflection event. We compare the two techniques of dipfrequency filtering and wave-destruction filtering, before integrating the two approaches and performing comparative analyzes on the optimal preservation of diffractions.
