Fractal Conservation Law And Its Applications In Seismic Noise Attenuation

At present, seismic prospecting is the most important geophysical method to obtain the information of petroleum and gas resources. This method utilizes the seismic wave generated by artificial excitation to obtain geological information, by which we cognitive the underground geological structure and locate the gas and minerals. With the help of seismic sensor,we can collect reflection signal which from the impulse signals we applied. However, as the over-exploitation of petroleum and natural gas, especially in shallow surface, the exploration turn into deeper layer. As we known,the deeper layer we explore, the longer the signal transmits, more serious the signal is attenuated, what’s important, some of the signals we received is totally submerged in noise. That’s the problem we get to solve, How to reduce the noise in the seismic data? At present, many effective methods have been put forward, under the condition that seismic data t be serious attenuated, these methods don’t works well. Hence, the exploration of the data processing method which can effectively simultaneous denoising and protecting the amplitude of sesismic signal at the same time, is of great significance.The research of this thesis includes the following two parts:1. We study the sesismic data processing method based on the fractal based on fractal conversation law, which is based on a PDE(partial differential equations) of Cauchy problem, which contains a pair of operators, one of them is Laplacian diffusion operator,and the other is anti-difussion operator, these two terms have opposite effects. The anti-diffusion is used to enhance the contrast, whereas the diffusion is used to reduce the noise. The tuning of the filter can be achieved by the control of the fractal exponent, which mainly are the amount of anti-diffusion and diffusion. It is proved that FCL is a fast and effective method to simultaneous denoising and enhancement of signals. Therefore, we analyze the basic principle of FCL, and use FFT to achieve the solution of partial differential equations, besides, we prove that FCL can be a effective method to proceed sesismic data.2. Notice that, for conventional FCL, The performance of FCL depends on the shape of the frequency response which is fixed, so there are some limitations on the filtering. Aiming at this lack, FCL based on correlation integral(CIRT-FCL) is proposed. With this new method, we use FCL under different parameters to filter noise seismic record, the signal is divided into several regions by correlation integral value, we can easily judge whether the segment containing effective signal, The segments with effective signal take different parameters of the FCL method with that do not contains effective signal. We know FCL filtering method based on the correlation integral have the better performance of denoising than the conventional FCL method.