Patent Document ID: 20100036614
Application ID: 11608155
Patent Flag: 0

Claim One:
1. A qualitative method to locate and dimension an oil, gas or water saturated zone in the earth, by extracting its characteristic resonance response in the range of 1-20 Hz to ambient noise, said method comprising the steps 1. measure over a survey area, where oil, gas or water are suspected or searched for, with long period seismometers for a certain duration each, either arranged in single manner or in arrays of several, producing seismograms, spacing chosen not larger then wave length of interest, typically 0.1-1 km, with a few reference measurements outside where fluids are suspected, or where fluids are known not to be present in the survey area, and at least a single permanent measurement, all locations chosen to avoid local noise and buried to avoid wind, while 2. simultaneously fluid saturated areas are passively excited by energy related to oceanic noise, industrial noise, close by oil-pump noise, tectonic noise, traffic noise, wind noise and other noise, 3. correct said seismograms of step 1 for local impedance changes, effect of topography and geological differences, regional noise patterns and possible tidal effects, 4. perform a main analysis of said seismograms in the frequency domain, consisting of frequency and phase, to (a) define average behavior of frequency and phase of oscillators over the entire duration of individual measurements, and also process said seismograms to obtain regional velocity correlation coefficients, deriving a matching the so obtaining said corresponding velocity dispersion assuming random waves, which can be matched to main modes of surface waves, and inverted to a velocity structure with depth, (b) use a horizontal/vertical component ratio test in said seismograms to exclude oscillations related to rock layering and rock structures alone and unrelated to fluid saturated areas (the horizontal to vertical component ratio reaches a maximum for rock structure oscillations), such frequencies are excluded from further consideration and optionally filtered out. (c) examine signal characteristics of said seismograms with shifted time windows, 1.5-30 sec size, to determine frequency peaks (in range 2-20 Hz), frequency peak, amplitude, sharpness, duration optionally including phase behavior, use frequency peak-repetitiveness to isolate oscillations as deviations in statistics from within standard noise, also isolate frequency peaks by use of a frequency/time/strength plot, and optionally filter seismograms for oscillations of detected frequency peaks for further processing, and (d) use the Sompi method on said seismograms, with or without filtering from steps b and c, to determine prevalent—if any—scillator parameters (frequency f and quality Q), (e) correlate shape and amplitude of signal to a depth-change indicator, related to smoothness in the amplitude distribution, (f) map frequency f from (a), (c), Q from (d), depth indicator from (e) over the survey area, thereby identifying suspect signal areas indicating resonance bodies, and g) set up and use statistics in time and space for comparisons of found resonator data from said seismograms related to fluids, frequency f, quality Q, depth indicator, frequency maxima from step c between different areas, where additional details are known—depth, fluid type, dimensions of fluid area, to deduce additional physical or geometrical properties in case of a match, whereby qualitatively identifying areas exhibiting prevailing resonance associated with said oscillators defined by parameters frequency peaks, quality Q, which are related to fluid saturated areas, since rock related effects were excluded in processing step 4b, mapping such areas of resonance regionally, and determining resonance area characteristics frequency f, quality Q.