Font Size: a A A

Research On The Technology Of Oil And Gas Reservoir Detection Based On The Theory Of Spectral Decomposition

Posted on:2011-01-15Degree:MasterType:Thesis
Country:ChinaCandidate:S FuFull Text:PDF
GTID:2180330464959286Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
The technology of seismic signal spectral decomposition is a popularization and application of the technique of joint time-frequency analysis in seismic data interpretation. It converts the seismic data from the time domain into the frequency domain. This conversion is the base of a series of important algorithms and technology of seismic data interpretation and processing. There are many methods of spectral decomposition of seismic signals, such as the WVD, short-time Fourier transform and wavelet transform. Each method has its own characteristics and limitations. In this paper, matching pursuits which is a flexible self-adaptive algorithm is used in spectral decomposition of seismic signals.Because of the flexible self-adaptation, matching pursuits algorithm as a more general algorithm of signal sparse decomposition has been quickly applied to many areas in signal processing. First, the algorithm in this paper decompose the signal into a linear sum of time-frequency atoms which best match the signal gradually. Second, it calculate the WVD of each atom, and pile up the time-frequency distribution of all the atoms to constitute the time-frequency distribution of entire signal. This method can effectively avoid the nuisance cross items of WVD. So it can get an excellent time-frequency distribution.But the problem of huge computational amount hindered its widespread application of signal processing. In order to solve the problem of huge computational amount, traditional MP algorithm has been improved in this paper after researching the theory. First, genetic algorithm is used to finding the best atom in each process of matching pursuits algorithm in order to reduce computational complexity. In order to improve the ability of local searching, downhill simplex algorithm is embedded in the genetic algorithm to further optimize the algorithm.To further increase the computing speed, some methods are used in order to reduce the computational amount in this paper, such as introducing FFT,changing the indexical range of atomic base, changing the scope of the inner product, and so on. The examples shows that this method can search the atom which best matches with the signal, and significantly reduce the computing time than the traditional MP algorithm. This algorithm can solve the bottleneck problem of huge computational amount in identifying oil and gas reservoir and other applications.In this study, a three-dimensional data volume is structured by putting several seismic signal together. The three dimensions are seismic trace, time and frequency. Cutting the three-dimensional data volume to the frequency slices can obtain the time-frequency distribution of the strata at different frequency. After comparing of the instant spectral energy at different frequencies, the energy abnormity at low-frequency can directly instruct the presence of oil or gas. The results show that the improved MP algorithm can be an efficient algorithm of spectral decomposition of seismic signal, and provide an effective means for hydrocarbon detection and reservoir description. This study demonstrates a well applied prospect of "low-frequency shadow" phenomenon in seismic data analysis and interpretation. It has important significance to the exploration of oil and gas reservoirs.
Keywords/Search Tags:matching pursuits, spectral analysis, hydrocarbon detection
PDF Full Text Request
Related items