misc 395 Flashcards
true or false
sonic log values are reciprocal of avg velocities
false
what are 2 properties of ideal wavelet?
all frequencies present w equal amplitude
true or false function of gamma ray log is to measure natural radioactivity of lithologic formations
true
true or false
constant velocity gather is created by nmo correcting a single cdp gather with a single velocity time pr from tzero to tmax
true
true or false
amplitude decay is partly due to spherical divergence
true
true or false
traces will properly align after nmo correction even if static shifts are not calculated and applied properly
false
true or false
refraction statics is a reflection event based method
false refraction based method
what does cvs stand for?
constant velocity stack
what does cdp stand for?
common depth point
what does vsp stand for?
vertical survey profile
what does nmo stand for?
normal moveout
name 2 migration algorithms
kirchhoff
finite difference
list full name of 3 types of gathers
shot gather- 1 shot all traces
common depth point- all traces by 1 reflector
common receiver gather- all traces by same geoph gr
common offset gather- traces w similar offsets
definition
impluse response
response of filter to input signal
cross correlation
comparison with similar traces
definition of migration
repositoon of dipping reflector
state 2 properties of zero phase wavelet
symmetrical
peak at zero
formula for comvolution
Rc * w(t) = s(t)
what are these cariables in the refraction statics formula?
Es - elevation of shot
Vw - velocity ofweathering layer
Ds - depth of shot
list 3 data types related to seismic frquency spectrum
conventional reflection 10-90Hz
hi res seismic 40-120Hz
sonic 10000-30000 hz
state 5 problems exploring for deep reflectors
s/n deterioration frequency resolution loss velocity isotropy multiples
what are 3 main shear wave sources
dynamite - limear charges or rows
anchored horizontal vibrators
directionally alternating horizontal hammer blows (x and y) against an anchored baseplate
name the 4 recording instrument units
amplifier
logic unit
tape unit
camera unit
name 3 reasons for amplitude correction
spreading loss
absorption
transmission loss
give the 2 displays used to find initial velocity function
CVGather- single velocity time pr to nmo corrected cdp gather.repeat w several velocity time prs
CVStack- velocity from CV Gather - nmo correct several cdp. derive new velocity function
list 4 data display types
wiggle trace
variable area
variable area w trace
variable density
name the 8 displays
inline crossline diagonal zigzag time slice horozontal slice perspective cube
basin dynamics and types of faults
extensional basin - divergent-normal fault
compressional basin - convergent- thrust fault
pull apart- shear- transform fault
describe halo-kinetic structures
salt structure that flows as a result of overburden
name 3 geophysical data groups
surface imagery by satellites and aircraft
near surface
deep penetration imagery
corrections for gravity surveys
free air correction- accounts for ht variations
terrain correction- accounts for hills n valleys
ship’s motion- etvos for marine
bouguer correction - accts for gravity effect of rock layers bet observ site, datum and sea level
match case study with a fact
foinaven fields, west shetlands UK
inversion of seismic data to impedence
match a case study to fact
brent field morthern north sea graben uk
p hydrophone and z ( vert geophone)
2 C
lamond field, central north sea graben uk
leakage of gas into overburden affects imaging
solution is multi component sensors and mode conversion of target zone, gas cliuds can be undershot
advantage of multi component data?
using mc sensors and relying on mode comversion at target zone gas clouds can be undershot
what’s the purpose of coherency interpretation?
structural interpretation
