Study Of Seismological Fluid Prediction By Two-phase BISQ

This thesis studies on how to calculate the stacked3D seismological data basedon the two-phase BISQ theory, and then get the instantaneous absorption spectra, andinstantaneous dispersion spectra, and how to detect underground fluid.After the high-resolution processing of the stacked seismic migration data,seismic trace is decomposed into25individual component signal sets with frequencyinterval being2Hz. Through calculation, we first get instantaneous amplitudespectrum, instantaneous frequency spectrum and instantaneous phase spectrum. Thenbased on the three instantaneous spectrums, we get instantaneous absorption spectrum,and instantaneous dispersion spectrum. Defined on the entire spectrum of the seismicsample points, the amount of information is amplified by25times, which serves asthe material basis of reducing multiple solutions. There are three physical quantitieson instantaneous absorption spectra and instantaneous dispersion spectra that areabsorption, dispersion and frequency. Absorption and dispersion are associated withthe permeability feature of formation while frequency is related to viscositycoefficient. The viscosity coefficient of the Two-Phase BISQ theory points out: Theexistence and movement of fluid causes the changes of absorption and dispersion,through which it detects fluid (Petroleum). Instantaneous absorption spectrum isdifferent from traditional absorption factors, which shows absorption informationchanges of different frequency, so it can thoroughly detect the changes of absorptionand dispersion. The huge difference between solid and fluid viscosity makes strongabsorption move towards the low-frequency direction of instantaneous absorptionspectra, so the instantaneous spectra deserves more concern of strong low-frequencyabsorption. In the interpretation, the geological background of hydrocarbonaccumulation and seismic parameters together are combined together to form thehydrocarbon prediction idea, hydrocarbon accumulation is two-phase media, onlywhen oil and gas are closed, can they be accumulated. The most essential geologicalinformation was neglected in the previous single-phase medium hydrocarbonprediction. Instantaneous absorption spectrum and instantaneous dispersion spectrum are not profiles, but rather transited from the time domain to the frequencydomain. The hydrocarbon information which is not resolved from the time domaincan be detected on instantaneous spectrums, the resolution is affected by the accuracyof the parameters and differences among parameters.According to the instantaneous absorption spectra, and instantaneous dispersionspectra, it’s predicted that there are two hydrocarbon traps in section one shoalreservoir, Maantang formation of Triassic carbonate rocks in Xiaoxin structural belt ofwest Sichuan region, and two hydrocarbon traps in Leikoupo Formation four ofunconformity reservoir. The predicted Hydrocarbon traps are in line with the knowndata of the three wells. The known well is predicted with the depth of5700meters,and thickness of4.3m.