misc 395 Flashcards

0
Q

true or false

sonic log values are reciprocal of avg velocities

A

false

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1
Q

what are 2 properties of ideal wavelet?

A

all frequencies present w equal amplitude

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2
Q
true or false
function of gamma ray log is to measure natural radioactivity of lithologic formations
A

true

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3
Q

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

A

true

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4
Q

true or false

amplitude decay is partly due to spherical divergence

A

true

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5
Q

true or false

traces will properly align after nmo correction even if static shifts are not calculated and applied properly

A

false

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6
Q

true or false

refraction statics is a reflection event based method

A

false refraction based method

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7
Q

what does cvs stand for?

A

constant velocity stack

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8
Q

what does cdp stand for?

A

common depth point

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9
Q

what does vsp stand for?

A

vertical survey profile

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10
Q

what does nmo stand for?

A

normal moveout

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11
Q

name 2 migration algorithms

A

kirchhoff

finite difference

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12
Q

list full name of 3 types of gathers

A

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

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13
Q

definition

impluse response

A

response of filter to input signal

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14
Q

cross correlation

A

comparison with similar traces

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15
Q

definition of migration

A

repositoon of dipping reflector

16
Q

state 2 properties of zero phase wavelet

A

symmetrical

peak at zero

17
Q

formula for comvolution

A

Rc * w(t) = s(t)

18
Q

what are these cariables in the refraction statics formula?

A

Es - elevation of shot
Vw - velocity ofweathering layer
Ds - depth of shot

19
Q

list 3 data types related to seismic frquency spectrum

A

conventional reflection 10-90Hz
hi res seismic 40-120Hz
sonic 10000-30000 hz

20
Q

state 5 problems exploring for deep reflectors

A
s/n deterioration
frequency resolution loss
velocity
isotropy
multiples
21
Q

what are 3 main shear wave sources

A

dynamite - limear charges or rows
anchored horizontal vibrators
directionally alternating horizontal hammer blows (x and y) against an anchored baseplate

22
Q

name the 4 recording instrument units

A

amplifier
logic unit
tape unit
camera unit

23
Q

name 3 reasons for amplitude correction

A

spreading loss
absorption
transmission loss

24
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
25
list 4 data display types
wiggle trace variable area variable area w trace variable density
26
name the 8 displays
``` inline crossline diagonal zigzag time slice horozontal slice perspective cube ```
27
basin dynamics and types of faults
extensional basin - divergent-normal fault compressional basin - convergent- thrust fault pull apart- shear- transform fault
28
describe halo-kinetic structures
salt structure that flows as a result of overburden
29
name 3 geophysical data groups
surface imagery by satellites and aircraft near surface deep penetration imagery
30
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
31
match case study with a fact | foinaven fields, west shetlands UK
inversion of seismic data to impedence
32
match a case study to fact | brent field morthern north sea graben uk
p hydrophone and z ( vert geophone) | 2 C
33
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
34
advantage of multi component data?
using mc sensors and relying on mode comversion at target zone gas clouds can be undershot
35
what's the purpose of coherency interpretation?
structural interpretation