عنوان مقاله [English]
Salt dome is a diapir shaped structure of salt that intrudes vertically through sediment layers and surrounding strata due to its low density. Salt area identification, determining its boundaries and its 3D modeling in seismic data is a crucial issue in the literature of the seismic data interpretation. Due to its high impermeability characteristic, it can form stratigraphic oil traps by sealing the hydrocarbon reservoirs and also could be used as underground storage for natural gas and disposal sites for hazardous waste such as isolation nuclear waste and creation of the compressed air reservoir. The steeply dipping complex-shaped structures related to the salt movement and significant difference in seismic wave propagation velocity inside the salt dome with the enclosed media, imposes significant challenges for seismic data processing and interpretation. Identification and delineation of salt body is a key step in seismic data processing and interpretation, which can help geophysicist to overcome aforementioned problems. In reflection seismic methods, salt boundaries are more often characterized by change of seismic character of the signal also called texture. There are several methods available for texture analysis in image processing that can be divided into seven classes which are statistical analysis, structural methods, transform based approaches, model-based methods, graph-based techniques, learning based strategies and entropy-based methods. Textural attributes characterize the spatial arrangement of neighboring amplitudes. Extraction of seismic texture attributes can be performed using spectral information of image such as Gabor filters and local 2D Fourier spectra. Dip, similarity and coherence are the common structural attributes which are used generally for textural analysis in seismic data. The most common rational approach to describe the texture in seismic image is to measure the statistical properties of the image. Gray Level Co-occurrence Matrix, chaos and variance are three conventional statistical seismic texture attributes used for this purpose. Due to the textural contrast of the salt dome with the surrounding layers and sediments, edge detection tools can also be used to determine the boundaries of textural changes and delineate the salt area. In this study, we used a new textural seismic attribute known as the gradient of texture to characterize the change of seismic character between the salt body and its surrounding geology. It calculates the texture gradient in two adjacent windows around a sample in different directions. It is supposed that different area in seismic image with different textural pattern will exhibit diverse gradient of texture. Thus, it will be appropriate for image segmentation for specific interpretation investigation. The gradient of texture attribute will differentiate desired area from the rest of the image through supervised classification and growth strategy in extending the selected classes. Efficiency of the introduced method for salt dome delineation and modeling in seismic data was investigated here by applying on a synthetic model and 3D seismic data from the Persian Gulf. Comparison between obtained results of the proposed method and conventional attributes revealed superiority of the 3D texture gradient in textural segmentation and salt dome modeling from seismic data.