Research On Imaging Method Of Complex Structure

The exploration of these years shows that the oil geologic condition of China is very complicated, the depth of oil and gas is deep and concealed. The situation of oil and gas resource exploration becomes more and more difficult. Facing such a hard situation, seismic exploration is required to enclose more rigorous information with details. Complex structure imaging is a focus in the field of seismic exploration lately. Imaging the complex structure underground earns great application significance and practical value for increasing the hitting rate of target and decreasing the risk of exploration. The research work on theory and realizing techniques of complex structure imaging has been a hard problem to solve urgently.The classical elasticity mathematics theory was established for ideal medium abiding Hooke law grimly, the earth medium is a viscoelastic medium with viscosity in fact, so elastic wave equation can not be used to describe the propagation of seismic waves in real media. The viscosity of the medium will cause dissipation of seismic energy, thus decreasing the amplitude and modifying the frequency content of the propagating wavelet. In order to obtain accurate information and imaging with high distinguishability from seismic data, the propagating rule of wave in viscoelastic medium should be studied. The medium described with modified Stokes viscoelastic wave equation is a Kelvin solid, which can be used to study the propagating of seismic wave in earth media. The characteristics of attenuation and dispersion of seismic wave in viscoelastic medium is discussed with emphasize on the base of Stocks viscoelastic wave equation. An important conclusion that the weak dispersion of low frequency component of seismic wave can be ignored. Through the Fourier transformation and complex operation, the basic algorithm of forward and migration of Stokes viscoelastic wave euqation in uniform viscoelastic medium is deduced successfully for the first time. On this basis, poststack migration algorithm and prestack depth migration algorithm of Stokes viscoelastic wave equation are put forward to fit velocity variety both in vertical and horizontal, and the numerical simulation are pursued separately. In some research, the earth medium was regarded as standard linear solid to study the propagating rule of wave in viscoelastic medium. From this view, the migration algorithm of linearIllviscoelastic wave equation is deduced in frequency field. The absorption is computedby complex velocity, but it is impossible to measure. A resolution to acquire thecomplex velocity with quality factor is described in this paper also.The basis of complex structure imaging is establishing velocity model, thevelocity inversion is a nonlinear problem. The neuraI network developed in these yearshas a characteristic of solving nonlinear mapping with extremity complexity. The back-propag8tion algorithm of neural network is modified, and the velocity analyzingmethod based on neuraI network is investigated, which can be used on .velocityanalyzing in both prestack field and migration fieId. This method shows a strongadaptability to noise. The migration velocity analysis has many advantages such asprecision and fixing on velocity distributing exclusively. The migration velocityanaIysis based on viscoelastic wave equation is developed in this paper.The principle of comprehensive utiliZaion of multi-course and different methodshas been a guiding line in complex structure imaging. For apriori information being animportant precondition, imaging plans based on aPriori infOrmation and nonaprioriinformation are put forward separate1y. The complex structure imaging is a dataprocessing with a great number of computation and need high density computingtechnology, which limits the improvement of imaging. To break such a limit, adistributing computation based on Agent is brought forward in the fina1 part of thispaper, the technique of data processing based on Agent is induced in seismi...