Technology Research And Application On Thin Interbed Detection Based On Seismic Wave Frequency Attributes

Oil exploitation industry pays more and more attention on thin interbeddedreservoir gradually, and how to use existing technology to carry out effectivedistinguishing, tracing and application for the thin interbedded reservoirs becomes ahot issue for geologists currently. As the thin interbedded reservoir has low thickness,complicated structure, poor horizontal continuity and strong anisotropy, it is verydifficult to use traditional spectral analysis for distinguishing. With the continuousincrease in difficulities of oil and gas resources exploration and mining, it is necessaryto make innovations to substitute the conventional distinguishing method for thininterbed, and produce forward new technological.We study the methods and theories of weighted integral energy spectrum andhigh-resolution complex trace analysis technique on the basis of the conventionaldistinguishing method of thin interbedded reservoir, and apply them in twodimensional seismic data of the east work area of Changde, and Longjiabao coal fieldwork area at the south of the eastern edge of Songliao Basin. Research contents andinnovation points mainly include:1. As seismic waves propagate in the oil and gas reservoir of the thin interbed, ifthe distance between the top and bottom interfaces of the oil and gas reservoir is lessthan the wave lengths of the seismic waves, we will observe the reflected wave fieldof the oil and gas reservoir of the thin interbed as the complex wave form, instead ofsingle wave form. Thus the research on the features of the complex wave is the keyfor distinguishing seismic data of the thin interbedded reservoir. By makingexperiments for several models, the paper studies the waveform characters of theseismic wave propagating in the thin interbedded reservoir, and discusses the relationbetween the depth of the thin interbed and the amplitude of reflected wave, as well asfrequency characters of seismic waves spreading in the thin interbed.Then, we makes detailed description on the characteristic changes of complex wave from the aspectsof band width, wavelet phase, and spectrum form, etc.2. Current integral energy spectrum has obtained acceptance as a method todistinguish the thin interbedded reservoir. The paper analyzes the critical researchproblems for the integral energy spectrum, and sums up the correspondingrelationship between the amplitude of the amplitude spectrum and the integral energyspectrum curve by comparing the integral energy spectrum and the amplitudespectrum on the thin interbed with formation conditions of different stratum depths ofthe one-dimensional monostratum and different stratum depths with uniform interval,and the thin interbed with different intervals. Meanwhile,the method utilizes thephenomenon in the actual seismic data processing, and obtains the pattens ofchanging of the integral energy spectrum at the tuning thickness position.3. On the basis of the conventional calculation and application of the integralenergy spectrum, the author investigates the weighted integral energy spectrum, andapplies it in the processing of seismic profile. By comparing it with integral energyspectrum, the weight coefficient of the seismic data after weighted integral energyspectrum processing has corresponding physical significance, and the obtained resultcan reflect the stratum characters more accurately, that is, the pattens of changing ofthe thin interbed at the tuning thickness position becomes more obvious, and theresolution of the reservoir is significantly improved.4. Complex trace analysis is commonly a key technique for thin stratumdistinguishing, and it can be adopted in research on the regular seismic exploration.However, its accuracy can not satisfy the requirement for research on thin interbeddedreservoir description. Based on the complex trace analysis method, the paper studiesthe complex trace analysis with high resolution, extracts three instantaneousparameters with high resolution (namely, instantaneous amplitude, instantaneousphase and instantaneous frequency), and applies them in seismic profile processing.Thus, the effect of resolution is significantly improved. Besides, it also adopts thecalculation method of weighted integral energy spectrum, it verifies the applicationeffect of the combination of the two methods in distinguishing thin interbedded reservoir in actual seismic data. Therefore, the distinguishing becomes more accurateand reliable.