WHY 3D?
WHY 3D?
SUB SURFACE FEATURES OF INTEREST IN HYDROCARBON EXPLORATION ARE THREE DIMENSIONAL IN NATURE. IN ORDER TO HAVE ADEQUATE AND DETAILED IMAGE OF THE SUBSURFACE, IT IS ESSENTIAL TO USE 3-D IMAGING TECHNIQUE.
ADVANTAGES OF 3D
IMAGING OF SUB SURFACE
RESERVOIR GEOPHYSICS
IMAGING OF SUB SURFACE
DELINEATION OF 3D SUBSURFACE FEATURES USING 2D SURVEYS OFTEN LEADS TO AMBIGUITY.THE SUBSURFACE GENERALLY DIPS IN MANY DIRECTIONS IN AREAS WHERE STRUCTURAL TRAPS ARE BEING EXPLORED.RESERVOIR GEOPHYSICS
RESERVOIR GEOPHYSICS
RESERVOIR GEOPHYSICS
APPLICATIONS OF
3D SEISMIC DATA
RESERVES
VOLUME
WELL/PLATFORM
LOCATIONS
WELL/PLATFORM
LOCATIONS
RECOVERY
STRATEGY
1.bin3D DATA ACQUISITION
PROJECT PLANNING
KEY WORDS
SWATHINLINE /CROSSLINERECEIVER /SHOTLINESRECEIVER / SHOT INTERVAL3D FOLDBIN SIZEKEY WORDS ( CONTD )
MIGRATION APERTUREFRESNEL ZONEEVEN FOLD DISTRIBUTIONEVEN OFFSET DISTRIBUTIONREDUNDANT MULTIPLICITYNON REDUNDENT MULTIPLICITYAZIMUTHFIELD PARTY SET UP
2.binFIELD EQUIPMENT
SEISMIC CABLESGEOPHONESRECORDING INSTRUMENTMAGNETIC TAPESSHOOTING SYSTEMSCOMMUNICATION SETSSHOT HOLE DRILLING ENERGY SOURCESTRANSPORTATIONENERGY SOURCES
DYNAMITE (LAND)VIBROSEIS (LAND)AIRGUN (OFFSHORE)SHOT HOLE DRILLING
MANUAL DRILLING JET BORINGTRUCK MOUNTED RIGSPRE PLANNING
PROGRAMME RECONNAISSANCEPROJECT REPORTPROCUREMENT / COLLECTION OF REQUIRED EQUIPMENTDATABASE
GEOLOGICAL/INTERPRETATIONAL OBJECTIVESGRAVITY ANAMOLY MAPSTOPO SHEETS OF THE AREAPREVIOUS SEISMIC WORK DONE RELEVANT SEISMIC SECTION TIME STRUCTURE MAPSWELL DATA / VSP DATAEXPERIMENTAL WORK
UP HOLE SURVEYSHALLOW REFRACTION SURVEYNOISE ANALYSISFOLD BACK EXPERIMENTFORMULA FOR MULTIPLICITY
MULTIPLICITY =( N*S)/(2*n)N= no. of channels in the spreadS = no. of shot points for the spreadn = no. of stations by which thespread is advanced
EXAMPLE
MULTIPLICITY =( N*S)/(2*n)If N = 48, S = 1, n =1, then M = 24If N = 48, S = 1, n =2, then M = 12If N = 96, S = 1, n =1, then M = 48If N = 96, S = 1, n =2, then M = 24OFFSET DISTRIBUTION
IDEALLY , IT IS DESIRABLE TO HAVE A WIDE SELECTION OF OFFSETS FOR EACH COMMON- CELL GATHER. OTHERWISE SMALL ERRORS IN MOVE OUT CORRECTION MAY CAUSE TRACE TO TRACE CHALTER ON STACKED ON SECTIONS.
EVEN OFF SET DISTRIBUTION
NEAR 12 NEAR MIDDLE 12FAR MIDDLE 12FAR 123D GEOMETRIES
SWATH PATTERNBRICK PATTERNSEIS LOOPSEIS SQARE#1
#60
SWATH 3D GEOMETRY
#61
#120
#121
#180
#181
#240
R1
R2
R3
R4
S4
4 R/L - R1, R2, R3, R4 & S/L - S4
G.I = 50M, SP.I = 100M, BIN SIZE = 25M X 50M
R/L INT.=100M, S/L INT.=100M, NEAR OFFSET = 300 & 350M
#1
#60
BRICK PATTERN 3D GEOMETRY
#61
#120
#121
#180
#181
#240
R1
R3
R5
R7
S5
S6
S7
S8
4 R/L - R1, R3, R5, R7 & 4 S/L - S5, S6, S7, S8
G.I = 50M, SP.I = 100M, BIN SIZE = 25M X 50M
R/L INT.=200M, S/L INT.=100M, NEAR OFFSET = 300 & 350M
SHOOTING DIRECTION
STRIKE LINE SHOOTING45 DEGREE FROM DIP DIRECTIONDIP LINE SHOOTINGMARINE ACQUISITION
THE MOST COMMON MARINE 3D DATA ACQUISITION INVOLVES SHOOTING A NUMBER OF CLOSELY SPACED PARALLEL 2D LINESBIN
A BIN IS A SMALL SUB SURFACE AREA WHICH DEFINES ONE SET OF RECORDED TRACES TO BE STACKED TOGETHER IN PROCESSING.
BIN SIZE = G.I X S.I
MIGRATION
MIGRATION IS THE PROCESS OF MAKING THE REFLECTION SURFACE COINCIDE WITH THE GEOLOGICAL SURFACE BY MOVING OR MIGRATING EACH REFLECTION POINT TO ITS PROPER POSITION IN THE SUB SURFACE.
MIGRATION APERTURE
THE NUMBER OF TRACES TO BE INCLUDED IN THE STACK.
THE SIZE OF THE APERTURE DEPENDS ON DIP, REFLECTION TIME OF THE EVENTS ON THE UNMIGRATED SECTION AND VELOCITY.
MIGRATION APERTURE NEED NOT BE SAME IN ALL DIRECTIONS AS IT DEPENDS UPON THE STEEPNESS OF DIPS AT THAT END.
FRESNEL ZONE
THE CHANNEL SPACING HAS BEARING ON A LATERAL RESOLUTION. REFLECTED ENERGY REPRESENTS SAMPLING NOT FROM A SINGLE POINT, BUT FROM AN AREA ON THE REFLECTING SURFACE. THIS AREA IS CALLED FIRST FRESNEL ZONE. ITS RADIUS R IS GIVEN BY,R= D/2 WHERE D IS DEPTH OF REFLECTING SURFACE AND IS WAVE LENGTH OF REFLECTED ENERGY.S
A
B
/4
FIRST FRESNEL ZONE
R
D
R= D /2
DETERMINATION OF FRESNEL ZONE RADIUS
BASEMENT CONFIGURATION
GEOMETRIC
FRAME WORK
ROCK / FLUID PROPERTIS
FLOW
SUEVEILLANCE
3D SEISMIC DATA
SURVEYOR
DRILLER
FIELD OBSERVER
QCO
PARTY CHIEF
SUPERVISOR