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Published byWillis Simon Modified over 9 years ago
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EXPLORATION GEOPHYSICS
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EARTH MODEL
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NORMAL-INCIDENCE REFLECTION AND TRANSMISSION COEFFICIENTS WHERE: 1 = DENSITY OF LAYER 1 V 1 = VELOCITY OF LAYER 1 2 = DENSITY OF LAYER 2 V 2 = VELOCITY OF LAYER 2 DENSITY 1 VELOCITY V 1 DENSITY 2 VELOCITY V 2 REFLECTION COEFFICIENT TRANSMISSION COEFFICIENT
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SEISMIC ACQUISITION
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GEOPHONE STRUCTURE
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GEOPHONE TYPES & FREQUENCY
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SOURCE TRUCKS
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3D-SEISMIC COVERAGE
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CDP & FOLD STACK
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MARINE SEISMIC CABLE LAYOUT
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MULTIPLE RAYPATH
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FACTORS AFFECTING AMPLITUDE
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ATTENUATION TECHNIQES
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SEISMIC DATA PROCESSING
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PROCESSING FLOWCHART
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OBJECTIVE OF PROCESSING REAL EARTH EARTH PROPERTIES PULSE SEISMIC TRACE PROCESSING MODEL EARTH
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EFFECT OF STACKING ON NOISE SIGNAL PLUS RANDOM AT SIX-DETECTOR ARRAY SIGNAL SIGNAL + NOISE NOISE SIGNAL + NOISE EACH RECEIVER SUMMED OUTPUT
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SEISMIC-WELL TIES PURPOSE: TO COMBINE TWO DATA SETS FOR A MORE COMPLETE INTERPERATION SEISMIC DATA TWO WAY TIME SEISMIC VELOCITY SEISMIC IMPEDENCE SEISMIC SEQUENCES SEISMIC FACIES STRUCTURE WELL DATA LINEAR DEPTH VELOCITY DENSITY GEOLOGIC AGE LITHOLOGY FAULT ORIENTATION
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ACOUSTIC STRUCTURE OF EARTH LAYERED EARTH SONICDENSITYRC
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CONVOLUTION
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DETAILED SYNTHETIC SEISMOGRAM
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POST-STACK PROCESSING RESIDUAL STATICS DISPLAY ENHANCEMENT MIGRATION ATTRIBUTE ANALYSIS INVERSION TIME-DEPTH CONVERSION
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SUMMARY OF SEISMIC PROCESSING DATA ARE GATHERED AND CMP-ORDERED GATHERS ARE FORMED VELOCITY ANALYSIS IS PERFORMED ON SELECTED GATHERS THE GATHERS ARE MOVEOUT CORRECTED, STACKED, AND PLOTTED STACKING MAY BE FOLLOWED BY ADDITIONAL PROCESSING
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VELOCITY ANALYSIS NORMAL MOVEOUT (NMO) X TXTX = T X - T 0 IMAGE POINT WHERE T 0 = ZERO OFFSET TIME T0T0 T0T0
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NMO-ISOTROPIC LAYER A X C Z IMAGE POINT B D WHERE THEREFORE
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MULTI-LAYER CASE FOR LAYER 1: FOR LAYER 2: V NMO = NORMAL MOVEMEOUT VELOCITY ASSUMED RAYPATH FOR V NMO CALCULATION X T X,1 Z V1V1 T 0,1 T 0,2 T X,2 ACTUAL RAYPATH
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HOW IS VNMO DETERMINED? FOR EACH TRACE T AND X VALUES ARE DETERMINED
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VELOCITY ANALYSIS HYPERPOLA PLOTS AS A STRAIGHT LINE ON T 2 - X 2 GRAPH T 2 - X 2 PLOT X2X2 OFFSET 2 t2t2 Y=b+mX WHERE
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VMNO CORRECTION KNOWING THE VNMO, T AND OFFSET, THE TIME CORRECTION NECESSARY TO SHIFT EACH TRACE CAN BE CALCULATED
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INTERVAL VELOCITY DETERMINATION FROM SEISMIC FROM VELOCITY ANALYSIS, WE KNOW VNMO 1,T 0,1 VNMO 2, T 0,2 SUBTITUTING THESE VALUES INTO THE DIX EQUATION
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MIGRATION EFFECTS FLAT HORIZONS REMAIN UNCHANGED IF THERE ARE NO VELOCITY ANOMALIES ABOVE DIPPING HORIZONS BECOME STEEPER, SHALOWER, AND MOVE LATERALLY UPDIP SYNCLINES BECOME BROADER, WITH ANY BOW TIES ELIMINATED ANTICLINES BECOME NARRWER DIFRACTIONS COLLPSE TO POINTS
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RAY PATH MIGRATION WHERE = TRUE DIP OF REFLECTOR = APPERENT DIP OF REFLECTOR V= VELOCITY REFLECTION REFLECTOR x t
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WHY MIGRATE? IF BEDS ARE DIPPING, APPERENT POSITION OF EVENTS ON A STACKED SECTION DIFFERS FROM THEIR TRUE POSITION DEPTH MODEL DEPTH TIME ARRIVAL TIMES 7 KFT/SEC 11 KFT/SEC 9 KFT/SEC
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ASSUMPTION UNDERLYING MIGRATION ALL EVENTS ARE PRIMARIES- NO NOISE, NO MULTIPLES, NO SHEAR WAVES ALL EVENTS COME FROM THE PLANE VERTICALLY BENEATH THE SEISMIC LINE- NO SIDEWIPE VELOCITY ARE KNOWN EVERY WHERE
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MIGRATION MOVES DIPPING HORIZONS
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FOCUSING EFFECT OF A SHARP SYNCLINE
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DEFOCUSING EFFECT OF AN ANTICLINE
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FOCUSING EFFECT OF A SYNCLINE
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3-D MIGRATION ELIMINATES ASSUMPTION OF 2--D MIGRATION THAT ALL DATA COMES FROM WITHIN PLANE OF SECTION REQUIRES 3-D DATA COLLECTION TO INSURE CLOSELY SPACED TRACES IN BOTH X, Y DIRECTIONS MOVES ENERGY IN BOTH INLINE AND CROSSLINE DIRECTIONS INLINES AND CROSSLINES TIE AFTER 3-D MIGRATION MAP MIGRATION IS AN ALTERNAIVE FOR COARSE GRID OF 2-D LINES
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TIME VS. DEPTH SECTIONS
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CDP GATHER AFTER DEMULTIPLEXING
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CDP GATHER AFTER AMPLITUDE CORRECTION
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CDP GATHER AFTER DECONVOLUTION
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VELOCITY ANALYSIS
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CDP GATHER AFTER NMO CORRECTION
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CDP GATHER AFTER MUTING STRETCHED ZONES
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CDP STACKED SECTION
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CDP STACKED SECTION WITH TVF FILTER
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