Computer-implemented method and system for small cave recognition using seismic reflection data

A computing system apparatus programmed to perform a set of operations of a computer-implemented method for small cave recognition using seismic reflection data, comprising:

• a computer system device for inputting, setting, selecting, outputting, and performing the operations of retrieving, computing, generating, invoking, determining, converting, and correcting;
• a memory resource, for storing data corresponding to the operations of inputting, generating and retrieving, a surface seismic reflection data in time-domain, a well log data represented in time-domain, a final migration velocity model, a source wavelet, a final reverse time migration image gather in depth-domain, a final reverse time migration image gather in time-domain, a final root-mean-square velocity model in time-domain, a residual normal moveout corrected image gather, a residual normal moveout corrected image gather, a final flattened image gather, an initial intercept volume, an initial gradient volume, a final intercept volume, a final gradient volume, a small cave identification model, a user-defined flatness value, an initial migration velocity model, an initial Kirchhoff pre-stack depth migration image gather, a set of initial moveout curves, a Kirchhoff pre-stack depth migration stacking image, a final reflector dip-angle image, a tomographic inversion model, a final Kirchhoff pre-stack depth migration gather, a generated flatness value, a current time-step value, a maximum time-step value, a source wavelet, a forward source-wavefield, a set of source propagated-angles for every source-wavefield, a backward receiver-wavefield, a set of receiver propagated-angles for every receiver-wavefield, a current image gather, a corrected image gather, a final root-mean-square velocity, a set of positive and negative residual normal moveout curves, an initial image gather, a set of relative time shifts for all seismic traces, and a trim statics correction time shift method;
• a non-transitory program storage computer-readable memory for performing the operations of inputting, setting, selecting, outputting, retrieving, computing, generating, invoking, determining, converting, and correcting;
• a computer system output device for outputting the operations of retrieving, computing, generating, invoking, determining, converting, and correcting;
• and
• a system computer, coupled to a computer system input device, coupled to a memory resource, coupled to a non-transitory computer readable memory device, and couple to the computer system output device, for performing the operations of:
• retrieving a surface seismic reflection data represented in time-domain, comprising data from seismic traces, acquired from a plurality of field receiving sensors;
• retrieving a well log data represented in time-domain, from a well hole containing a small cave;
• computing a final migration velocity model from the retrieved surface seismic reflection data and the retrieved well log data;
• retrieving a generated final migration velocity model from the computed final migration velocity model from the computed initial migration velocity model;
• computing a source wavelet from the retrieved surface seismic reflection data;
• generating the source wavelet from the computed source wavelet;
• retrieving the source wavelet from the generated source wavelet;
• computing a final reverse time migration image gather, using the retrieved surface seismic reflection data, the retrieved final migration velocity model, and the generated source wavelet, employing a finite difference method;
• retrieving the final reverse time migration image gather in depth-domain from the computed final reverse time migration image gather;
• converting the retrieved final reverse time migration image gather, from the depth-domain to the time-domain;
• generating a final reverse time migration image gather in time-domain from the converted final reverse time migration image gather;
• retrieving the final reverse time migration image gather in time-domain from the generated final reverse time migration image gather in time-domain;
• computing an initial root-mean-square velocity model in time-domain from the retrieved final migration velocity model;
• generating a final root-mean-square velocity model in time-domain from the computed initial root-mean-square velocity model;
• retrieving the final root-mean-square velocity model in time-domain from the generated initial root-mean-square velocity model;
• computing a residual normal moveout corrected image gather from the retrieved final reverse time image gather;
• retrieving a residual normal moveout corrected image gather from the computed residual normal moveout corrected image gather;
• computing a final flattened image gather from the retrieved residual normal moveout corrected image gather, employing trim statics correction method;
• retrieving the generated final flattened image gather from the computed final flattened image gather;
• computing a final intercept volume and a final gradient volume using the retrieved final flattened image gather;
• retrieving a generated final intercept volume and a generated final gradient volume from the computed final intercept volume, and the computed final gradient volume;
• computing a multiplication of the final intercept volume and the final gradient volume;
• and
• generating a small cave identification model from the multiplied intercept and gradient volumes.