Study On 3D Wave Equation Simulation Of Seismic Characteristics For Carbonate Reef And Bank Strata

The reef and bank are special kinds of carbonate sediments which possesses unique pore space, with a generally high porosity and permeability, and it is an excellent reservoir of oil and gas. According to the statistics, the proved reserves of natural gas and oil in marine carbonate rocks is more than 50% of the total world wide oil and gas reserves, in which 20% is the reef and bank. Because of its large reserve volume and high productivity, naturally reef and bank carbonate reservoirs are signified to our national petroleum strategy. The reef flat facies reservoir is widely distributed in the world as welll as in my county. But reef and bank strata is inhomogeneous and differential, quantity of seismic sections is usually poor, so it's very difficult to identificate and forecast reef and bank reservoir. It's extraordinarily significant to study on this item.In this paper, research was executed in two aspects. On one hand, characteristics of geology and seismic wavefield response about carbonate reef and bank were analyzed sysematically. On the other hand, seismic wavefiled numerical simulation by wave equation in frequency-wavenumber domain was studied typically. All kinds of geological model on reef and bank strata were created, then seismic wavefiled modeling and migration throuth wavefield continuation theory using wave equation were performed to these models. The schemes of seismic response from reef and bank strata were established by this way. The characteristics of reef and bank strata could be used to oil and gas exploration in carbonate rock.The paper has the following studies. First of all, briefly introducing the concept and classification of the reef and bank strata, and summed up the characteristics of seismic response patterns, sedimentary facies patterns, sedimentary environment. Secondly, two dimension closed structure geological models were created on the base of control points. Then wavefield forward modeling and migration to these models were perfomed by wave equation continuation theory in frequency-wavenumber domain, including three methods which were phase shift,phase shift plus interpolation,splitting step Fourier. Phase shift plus interpolation method was applying to theory reef and bank conventional time section seismic forward modeling, inducing 12 kings of typical reef seismic response models. Splitting step Fourier method was applying to generate simulational seismic records and migrated sections which had a good similarity compared with real reef records. Thirdly, the seismic response characteristics of carbonate reef and bank were so complex that there is a similarity with the igneous rock, mudstone and sandstone. In order to avoid these interpretation traps, wave eqution seismic wave field simulation is applied to the above geologic body and the differences of characteristics of seismic response between these geologic body and reef has been analyzed. Fourthly, based on the two-dimensionl forward modeling method, extending 2D wave-field extrapolation operator to 3D space in F-K domain and applying 3D wave eqution to realize fast post-stack forward modeling of real 3D geologic body undergroud.