VERTICAL SEISMIC PROFILING: SPECTRUM OFFSET INVERSION

MANY KNOWN OIL AND GAS RESERVOIRS HAVE A HETEROGENEOUS AND A MULTI-LAYERED STRUCTURE. EXISTING SEISMIC METHODS AIMED AT ANALYSIS OF THEIR STRUCTURE SUCH AS AMPLITUDE-VERSUS-OFFSET ANALYSIS HAVE LIMITED RESOLUTION AND ARE EFFICIENT ONLY FOR THE TARGET ZONES OF SIMPLE STRUCTURE. IT IS IMPORTANT TO DEVELOP A HIGH RESOLUTION METHODOLOGY FOR JOINT INVERSION OF MULTI-OFFSET, MULTI-SOURCE SEISMIC DATA FOR THE ESTIMATION OF SEISMIC PARAMETERS OF A MULTI-LAYERED REFLECTING TARGET ZONE IN THE CASES WHEN THE THICKNESSES OF INDIVIDUAL LAYERS MAY BE SMALLER THAN THE WAVE LENGTH. THIS WILL LEAD TO IMPROVED RESOLUTION OF GEOLOGIC STRUCTURES AND MORE EFFICIENT METHODS FOR DETECTION OF OIL AND GAS RESERVOIRS. SPECTRUM-VERSUS-OFFSET (SVO) METHODOLOGY GIVES A HIGH RESOLUTION IMAGING OF THE MULTI-LAYERED TARGET ZONE USING MULTI-OFFSET, MULTI-SOURCE INVERSION OF FREQUENCY-OFFSET FUNCTIONS. IN THIS METHODOLOGY, P AND (OR) S WAVES ARE USED AS INPUT DATA. THE LIST OF ESTIMATED PARAMETERS INCLUDES P AND S VELOCITIES, DENSITIES, AND THICKNESSES OF INDIVIDUAL LAYERS. THIS METHOD INCLUDES THE CALCULATION OF OFFSET-FREQUENCY SPECTRAL FUNCTIONS FREE FROM AN INFLUENCE OF THE SEISMIC SOURCE AND UPPER PART OF THE GEOLOGIC SECTION, FORWARD MODELING, INTERACTIVE INVERSION OF THESE FUNCTIONS, AND HIGH RESOLUTION IMAGING OF THE OUTPUT PARAMETERS. THE PHASE I PROJECT WILL DEVELOP A METHODOLOGY FOR THE ESTIMATION AND HIGH RESOLUTION IMAGING OF SEISMIC PARAMETERS OF A MULTI-LAYERED TARGET ZONE BASED ON ITERATIVE CONSTRAINED INVERSION OF SEISMIC DATA. IN PHASE II, SVO METHODOLOGY WILL BE EXPANDED TO INHOMOGENEITIES. SVO INVERSION OF P AND S WAVES WILL BE DEVELOPED.