Analysis Of Curvature Attribute And Its Application

The faults, fractures and development vug existed underground, whose physical properties and elastic properties are very different from surrounding rock after filled with weak substances (oil, gas, water and soft mudstone or sandstone) or not. This difference is the foundation of utilizing Geophysical methods to identify or examine faults, fractures and development vug. However, due to the spatial distribution of fracture-developed zones with the influence by various factors are often not certain regularity, so the characteristics of seismic wave field are no rules to follow. It's too hard to use conventional seismic wave field to track or compare the fractures, and the kinematic characteristics of seismic wave to identify and detect the fractures is useless too. A large number of studies have found that irregular wave field between fracture- developed zones and fracture-no developed zones have obvious edges or boundaries. Therefore, to identify or delineate the borders can be identified the spatial distribution of faults, the identification of fracture-developed zones is conversed to find the edge of the seismic wave field or singular value.This paper based on the study of the theory of curvature attribute and time-frequency domain filtering methods, in order to utilize and excavate the information of spatial orientation in three-dimension seismic data, analyses the scale of geological structure, geometry and spatial distribution, and restores the underground geological features. These can improve the accuracy and efficiency of structural interpretation of seismic data. In this article, the main research includes:(1) The analysis of curvature attribute and its application. In mathematics, curvature is used to measure the degree of the bending curve, and the analysis of curvature is used for curvature attribute which is utilized to calculate the spatial distribution of the geometric shape. Curvature attribute used to describe the geometry of geologic body, and they're corresponding to the bending of seismic reflectors. Curvature attribute is sensitive to bends, folds, fractures and faults, and they're the effective methods to find geological structural.Firstly, this article introduced the mathematical definition of curvature from the curve, combined with trend surface analysis and achieved the calculation of surface curvature attribute, listed common curvature attribute and described its characteristics. Second, this paper discussed the limitations of surface curvature attribute, and based on the instantaneous parameters, derived volumetric curvature attribute from three-dimension seismic data which included spatial orientation information. Third, the article utilized the ideas of multi-scale signal analysis, separated the structures with different wavelengths, and then achieved the computation of fractional volumetric curvature attribute. In order to highlight the structural features of a particular direction, constructed a method of calculating the oriented volumetric curvature attribute. On this basis, we let coherent attribute as the constraint condition of curvature attribute, then got a useful method of enhancement the weak structure features.Finally, the paper applied the curvature attribute to the theoretical model and actual data, both of them obtained good results. Through 3D visualization of curvature attribute, combined with seismic and geological data for interpretation and comprehensive analysis, so that we achieved the geological target.(2) Pre-processing for the analysis of curvature attribute.Quantity of seismic data is the basement of structure and lithological interpretation. Conventional methods for improving the signal to noise ratio will lose the horizontal resolution of the seismic, blur breakpoints, stratigraphic contacts and geological boundaries. Therefore, in order to maintain the faults and characteristics of boundaries, we introduced image structure information into filter methods, and proposed anisotropic diffusion filter.This paper described the basic theory of nonlinear anisotropic diffusion equation, discussed the effects of anisotropic diffusion filter with different structure tensor, and got two and three dimensional calculation of anisotropic diffusion filter through stable structure tensor. In order to preserve the discontinuity of fractured strata, we added the fault operator to control the iterative step. Applied anisotropic diffusion filter to real seismic data interpretation, it can enhance the coherence characteristics of seismic data, maintain the edge information and suppress the noise at the same time, and improve data quality. Compared with median filter, anisotropic diffusion filtering is more suitable for the calculation of curvature attribute.Acquisition footprint is caused by designing the observation system itself, it will be enlarged in data processing from time to time, remains in the seismic data, brings difficulties for seismic interpretation or artifact. Acquisition footprint will affect the signal to noise ratio of sections and vertical resolution, and damage structures details and reflected wave group features, so that directly affect the accuracy of reservoir description and the reliability of exploration.With the improvement of wavelet transform theory, the image analysis and processing technology based on wavelet has been used widely. Wavelet transform has multi-resolution characteristics, so it can be used for image restoration, noise reduction and other applications. This paper first described the concept and causes of acquisition footprint, listed common technique to eliminate acquisition footprint. Second, the article introduced the concept of continuous wavelet transform and discrete wavelet transform, analyzed and compared discrete orthogonal wavelet transform and discrete stationary wavelet transform, finally proposed an effective method which utilized two-dimensional stationary wavelet transform to eliminate acquisition footprint. We applied this approach to de-noising the actual three-dimensional seismic data and seismic attribute calculation of geometry, both of them had good results.