Locating oil or gas actively by exciting a porous oil and gas saturated system to give off its characteristic resonance response, with optional differentiation of oil, gas and water

A method to directly detect oil, water or gas in the earth, comprising the steps of

• performing set A of steps by
• seismically exciting a suspected fluid saturated region in the earth, the suspected fluid saturated region interacting with the surrounding rock as an oscillator when excited, constituting a fluid and rock system, said seismic excitation in the frequency range of 1-20 Hz, and
• simultaneously performing seismic measurements with long period seismometers in an area of interest above the suspected fluid saturated area, thereby producing seismograms;
• performing an interpretation of said seismograms, by transforming said seismograms into oscillator characteristics consisting of frequency and quality factor of the oscillator, on a computer by:
• eliminating first rock-only-structures caused oscillations by generating a Fourier spectrum from said seismic measurements, and applying a horizontal/vertical ratio test to said Fourier spectrum using maximums in the horizontal/vertical ratio for elimination of said rock-only-structures caused oscillations, and
• processing said seismograms with shifted time windows and independently as frequency/time/strength plots to determine frequency peaks of the oscillator, and
• performing a Sompi analysis giving frequency and quality factor of the oscillator, then
• mapping of frequency and quality factor of the oscillator over said area of interest to get dimensions of said oscillator,
• performing set B of steps, translating said frequency and quality factor of the oscillator into preliminary physical parameters of the fluid and rock system by using existing fluid mechanics model from Volcanology data, and numerical fluid pillow model data applicable to presently found geological/geophysical conditions in the area of interest,
• performing set C steps, validating said physical parameters of the fluid and rock system, by
• independent of set B of steps translating said frequency and quality factor of the oscillator to preliminary related physical parameters of the fluid and rock system by using theoretical fluid pillow model data,
• performing set D of steps, transforming seismic energy in said seismic measurements directly into the physical parameters of the fluid and rock system by a numerical model analysis
• using all prior gathered resulting preliminary related physical parameters of the fluid and rock system and dimension of said oscillator from set A-C of steps to set physical parameters of the fluid and rock system as starting values for said numerical model analysis,
• selecting a specific physical fluid in rock model best which represent the geological and geophysical conditions of fluid is found in rocks in the area of interest, described as cracks, fluid pillow or and other fluid containment
• performing said numerical model analysis using the selected physical fluid in rock model, using standard equations describing physics of fluid and rock, and using the applied seismic energy excitation as input to the numerical model producing synthetic seismograms,
• migrating said synthetic seismograms to the surface, and
• adjusting said physical parameters of the fluid and rock system and repeating said numerical model analysis till a good fit of said migrated synthetic seismograms with the seismic measurements is obtained,
• performing set E of steps, wherein coarsely differentiating between possible fluid types, by
• performing set B of steps while applying a Monte Carlo approach of varying the fluid parameters only of said physical parameters of the fluid and rock system while leaving other parameters constant;
• delivering a best fluid type from said varying of the fluid parameters,
• performing set F of steps, differentiating finely between fluids by
• performing said numeric model analysis of set D of steps while applying a Monte Carlo approach by varying fluid parameters, while rock parameters are kept constant of the fluid and rock system,
• selecting fluid parameters which give a best fit of said migrated synthetic seismograms to said seismic measurement,
• wherein the results of sets B-F of steps determine existence, extent, depth and type of fluid oil, water and gas, in an increasingly precise manner.