EXPLORATION GEOPHYSICS

EARTH MODEL

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

SEISMIC ACQUISITION

GEOPHONE STRUCTURE

GEOPHONE TYPES & FREQUENCY

SOURCE TRUCKS

3D-SEISMIC COVERAGE

CDP & FOLD STACK

MARINE SEISMIC CABLE LAYOUT

MULTIPLE RAYPATH

FACTORS AFFECTING AMPLITUDE

ATTENUATION TECHNIQES

SEISMIC DATA PROCESSING

PROCESSING FLOWCHART

OBJECTIVE OF PROCESSING REAL EARTH EARTH PROPERTIES PULSE SEISMIC TRACE PROCESSING MODEL EARTH

EFFECT OF STACKING ON NOISE SIGNAL PLUS RANDOM AT SIX-DETECTOR ARRAY SIGNAL SIGNAL + NOISE NOISE SIGNAL + NOISE EACH RECEIVER SUMMED OUTPUT

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

ACOUSTIC STRUCTURE OF EARTH LAYERED EARTH SONICDENSITYRC

CONVOLUTION

DETAILED SYNTHETIC SEISMOGRAM

POST-STACK PROCESSING RESIDUAL STATICS DISPLAY ENHANCEMENT MIGRATION ATTRIBUTE ANALYSIS INVERSION TIME-DEPTH CONVERSION

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

VELOCITY ANALYSIS NORMAL MOVEOUT (NMO) X TXTX = T X - T 0 IMAGE POINT WHERE T 0 = ZERO OFFSET TIME T0T0 T0T0

NMO-ISOTROPIC LAYER A X C Z IMAGE POINT B D WHERE THEREFORE

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

HOW IS VNMO DETERMINED? FOR EACH TRACE T AND X VALUES ARE DETERMINED

VELOCITY ANALYSIS HYPERPOLA PLOTS AS A STRAIGHT LINE ON T 2 - X 2 GRAPH T 2 - X 2 PLOT X2X2 OFFSET 2 t2t2 Y=b+mX WHERE

VMNO CORRECTION KNOWING THE VNMO, T  AND OFFSET, THE TIME CORRECTION NECESSARY TO SHIFT EACH TRACE CAN BE CALCULATED

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

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

RAY PATH MIGRATION WHERE  = TRUE DIP OF REFLECTOR  = APPERENT DIP OF REFLECTOR V= VELOCITY REFLECTION REFLECTOR x t

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

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

MIGRATION MOVES DIPPING HORIZONS

FOCUSING EFFECT OF A SHARP SYNCLINE

DEFOCUSING EFFECT OF AN ANTICLINE

FOCUSING EFFECT OF A SYNCLINE

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

TIME VS. DEPTH SECTIONS

CDP GATHER AFTER DEMULTIPLEXING

CDP GATHER AFTER AMPLITUDE CORRECTION

CDP GATHER AFTER DECONVOLUTION

VELOCITY ANALYSIS

CDP GATHER AFTER NMO CORRECTION

CDP GATHER AFTER MUTING STRETCHED ZONES

CDP STACKED SECTION

CDP STACKED SECTION WITH TVF FILTER