Method for determining underground fluid by seismic data

Abstract

The invention provides a method for determining subsurface fluid by seismic data obtained from geophysical exploration. The method comprises the following steps: converting the seismic data into bulk modulus and density data of the effective subsurface media; acquiring elastic modulus of the effective media at a borehole of a work area according to longitudinal and transverse wave log data; calculating the elastic modulus and the fluid modulus of the media at the borehole, porosity log data and pore aspect ratio spectrum data, low frequency model of solid matrix elastic modulus and the elastic modulus data volume of a dry solid matrix, separating well side fluid bulk modulus from the effective media bulk modulus which is inverted by the seismic data, and calibrating with the moduli of the borehole and well side fluid, and calibrating the moduli of other non-well side fluid by a calibration operator to identify the subsurface fluid. The method makes full use of the amplitude, frequency and phase information to invert the elastic modulus of the effective media, which reduces multi-resolution, breaks though the spherical void restriction and laboratory measurement requirements, and easily achieves the fluid modulus separation, and the fluid identification is direct, the result of the fluid identification is reliable, and the fitness of the fluid identification and well drilling result is up to more than 90%.

Description

technical field [0001] The invention relates to geophysical prospecting technology, and is a method for determining underground fluid by using seismic data. Background technique [0002] To identify and determine subsurface fluid based on seismic data, in addition to common attribute analysis and seismic inversion, the fluid modulus method has attracted more and more attention. Practice shows that the bulk modulus of natural gas is generally 0.02-0.1GPa, that of oil is about 1GPa, and that of water is greater than 2.25GPa. Therefore, the fluid modulus can be used to directly identify and determine the properties of pore fluids. [0003] At present, the methods of fluid identification using fluid modulus include velocity-model method and stochastic inversion method (Murphy, 1993). For sandstone formations, this method uses the Biot-Gassmann equation to extract fluid modulus from P- and S-wave velocities for measurement. Well data, the effect is relatively good, but the bigge...

AI Technical Summary

Problems solved by technology

This method requires a prior probability distribution function, and in the case of limited data, the reliability is low

Only using the amplitude information that changes with the offset to perform the inversion of the amplitude with the offset (AVO) to obtain the velocity data, so there are many defects such as multi-solution and difficult implementation

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