velocity estimation of friendswood’s weathering zone using fermat’s interferometric principle by...
DESCRIPTION
Motivation An accurate velocity distribution of the weathering zone is very important for accurately imaging the subsurface structure.TRANSCRIPT
Velocity Estimation of Velocity Estimation of Friendswood’s Friendswood’s
Weathering Zone using Weathering Zone using Fermat’s Fermat’s
Interferometric Interferometric PrinciplePrinciple
By Chaiwoot BoonyasiriwatBy Chaiwoot BoonyasiriwatUniversity of UtahUniversity of Utah
OutlineOutlineMotivation
Goals: Estimate Velocity Distribution
Problem and Solution
Results
Conclusion
Future work
MotivationMotivation
An accurate velocity distribution of the weathering zone is very important for accurately imaging the subsurface structure.
GoalsGoalsTo determine the horizontal velocity distribution of the weathering zones of the Friendswood field data.
To test the power of the Fermat’s interferometric principle.
OutlineOutlineMotivation
Goals: Estimate Velocity Distribution
Problem and Solution
Results
Conclusion
Future work
ProblemProblemGiven:
VSP gathers of the Friendswood field data
Find:
Horizontal velocity distributions of the weathering zones
Friendswood VSP Acquisition Friendswood VSP Acquisition GeometryGeometry
Shot
Geo-phone
24 Shots
98 Geophones
0 m0 m 92 m92 m
2.2 km/s2.2 km/s 3.6 km/s3.6 km/s
4300 ft/s4300 ft/s 6900 ft/s6900 ft/s
30 ft30 ft
1000 ft1000 ft25 ft25 ft 600 ft600 ft
CDPCDP
(Sen Chen et al, 1991)(Sen Chen et al, 1991)
WETWET
Friendswood TomogramsFriendswood Tomograms RTRT
Fermat’s Interferometric Fermat’s Interferometric PrinciplePrinciple
g”g”
ssgg
xx
Specular Ray
gg’’
x’x’
Diffraction Ray
0diff spec
''gsx'''gg ''sg0)( ''gsx '''gg ''sg
)(min''g ''gsx''sg'''gg
Velocity EstimationVelocity Estimation
where 22 ZXL
s g
/2LV ref
OutlineOutlineMotivation
Goals: Estimate Velocity Distribution
Problem and Solution
Results
Conclusion
Future work
Results: Shallow Results: Shallow ReflectorReflector
220
23522352 23522352 576576
)(min''g ''gsx''sg'''gg
''gsx''sg'''gg
Numbers of DataNumbers of Data
Results: Deep ReflectorResults: Deep Reflector
310
OutlineOutlineMotivation
Goals: Estimate Velocity Distribution
Problem and Solution
Results
Conclusion
Future work
ConclusionConclusion• Fermat’s interferometic principle is fast and
simple
• Horizontal velocity distributions of two reflectors in the weathering zones have been estimated
• The resulting velocities might not be accurate due to the inaccurate ghost arrivals and the simple method used to compute the velocities.
Future WorkFuture Work
• Use full reflection tomography to compute the horizontal velocity distribution.