METHOD AND APPARATUS FOR DETECTING FRACTURES USING FREQUENCY DATA DERIVED FROM SEISMIC DATA

摘要

Geologic formations containing fractures are an important source of hydrocarbon accumulations and an interesting target for geophysical exploration. The presence of fractures in a geologic formation will act as a high-cut filter on the seismic wave propagation, producing a measurable change in the frequency spectra of the seismic signal above the fractured zone compared to the frequency of the signal below the zone. A unique method has been developed to show the presence of fractures in an Earth formation as a mappable attribute. This method uses the frequency spectra derived from P-wave seismic data over a pair of specific time windows above and below a seismic horizon or reflector of interest to infer the presence or absence of to these geologic fractures based on an attenuation of high frequencies. The method produces a parameter value (t*) that is proportional to the shift in frequency spectra amplitudes (i.e., energy) from higher frequencies to lower frequencies, that is, from a time-window above a horizon or reflector of interest to a time-window below the horizon or reflector of interest.