Stratigraphy Using Wavelet Transform Analysis

Abstract

Wavelet (mathematical microscope) analysis of seismic data is useful for the precise subsurface imaging and interpretation of thin beds. Three-dimensional (3-D) seismic data interpretation for the subsurface imaging of thin-bed contourite systems is an important aspect of such research. The method enables the seismic expression of bottom current deposits to be distinguished from that of other related deep-water sediments (such as turbidites, hemipelagites, and debrites), and the information that can be derived from seismic data to be maximised. A wide variety of seismic facies are common in contourites, most of which are equally present in turbidite systems. Seismic facies associations that may be typical of contourites are yet to be defined. Seismic characteristics also depend very closely on the methods of seismic acquisition and processing. Sediment waves and channels are very common in both contourite and turbidite systems, and are not specifically diagnostic of either system. Slope deformation, sediment creep, and large-scale water-escape may cause a hummocky seismic facies that can be misinterpreted as sediment waves. The identification of hydrocarbon reservoirs from seismic data is a key issue in the oil industry. Texture segmentation of a 3-D seismic section with wavelet transform is employed for pattern recognition. Because of the segmentation, zones of different internal stratification are identified in the seismic section. This recognition is based on the comparison of 3-D seismic data with the reference patterns extracted from representative areas, characterized by different textures. In splicing 3-D seismic data, consistent processing is one of the key technologies because this has a large influence on imaging quality. The goal of seismic geomorphology is to look for and recognise geologically or geomorphologically meaningful patterns in plan view as well as in section view. Seismic geomorphology, the extraction of geomorphological insights using predominantly 3-D seismic data, is a rapidly evolving discipline that facilitates the study of the subsurface using plan-view images. Methods are being evolved for generating horizontal and flat slices, producing arbitrary traverses, performing wavelet attribute extractions and mapping, and rapidly analysing large, complex data volumes. A geological feature must have an expression that is scientifically reasonable in multiple dimensions. Analysis of section view images integrated with plan-view images represents the integration of seismic stratigraphy with seismic geomorphology. Pattern recognition, where the interpreter is able to recognize geologically significant features in plan view on 3-D seismic data, is critical to the seismic geomorphological approach. In addition, it is also essential to cross-reference plan-view images with section-view images, thus integrating the geomorphology with the stratigraphy.