B Fractures
Fractures and impedence
Fractures and impedence
direct sources of information on fractures
core analysis
(low core recovery, likely induced if conchoidal or very irregular)
indirect sources of fracture information
well logs
well testing
production history
main log technique for detecting fractures
electrical image logs
3 classifications of fracture fill
open
cemented
induced
4 classifications of fractured reservoirs
1: fractures procide essesntial reservoir porsity and permeability
2: fractures provide the essential reservoir porosity
3: fractures assist permeability
4: fractures provide no porosity or permeability but create significant reservoir boundaries.
what is shear wave splitting
shear waves travelling in two orientations in same direction, one is slowed by fractures in a single orientation-waves are split.
effective pressure vs. lithostatic pressure
effective pressure: the pressure bourne by the framework of the solids of the porous media
lithostatic pressure: the pressure exerted by the total weight of rocks and interstitial fluids at a certain depth
many overpressured rocks are associated with...
this means what for detection...
undercompacted shales, means they can be observed as anomalous low velocities on seismics
porosity density and velocity graphs for undercompaction
.
forward modelleing vs. inverse modelling
Stratigraphic Layered Earth Model - produces - synthetic seismic response - FORWARD modelling Observed Seismic Response - produces – stratigraphic layered Earth model – INVERSE modelling
How do you calculate impedance
Velocity x Density
Attenuation is
amplitude loss
frequency dependent attenuation
.
frequency independent attenuation
.
What is acoustic impedence inversion
The inversion of reflection seismograms into synthetic acoustic impedance sections
benefits of impedence data
(3) +1
rock properties don't tell gradational changes rock properties Impedance (Velocity x Density) is a rock property and not an interface property like reflectivity Wavelet complexity such as tuning is diminished such that interfaces become simpler Acoustic impedance volumes incorporate the gradational changes in rock properties not imaged by seismic reflectivity i.e. focuses attention on layer variations Acoustic impedance is closely related to rock properties of interest such as lithology, porosity and pore fluid fill – we relate them via empirical relationships
two different types of impedence inversion algorithms
trace based
model based
How to measure Q
capture wavelet at two points on a colinear path, use the difference to calculate Q
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Lernkarten
direct sources of information on fractures
core analysis
(low core recovery, likely induced if conchoidal or very irregular)
indirect sources of fracture information
well logs
well testing
production history
main log technique for detecting fractures
electrical image logs
3 classifications of fracture fill
open
cemented
induced
4 classifications of fractured reservoirs
1: fractures procide essesntial reservoir porsity and permeability
2: fractures provide the essential reservoir porosity
3: fractures assist permeability
4: fractures provide no porosity or permeability but create significant reservoir boundaries.
what is shear wave splitting
shear waves travelling in two orientations in same direction, one is slowed by fractures in a single orientation-waves are split.
effective pressure vs. lithostatic pressure
effective pressure: the pressure bourne by the framework of the solids of the porous media
lithostatic pressure: the pressure exerted by the total weight of rocks and interstitial fluids at a certain depth
many overpressured rocks are associated with...
this means what for detection...
undercompacted shales, means they can be observed as anomalous low velocities on seismics
porosity density and velocity graphs for undercompaction
.
forward modelleing vs. inverse modelling
Stratigraphic Layered Earth Model - produces - synthetic seismic response - FORWARD modelling Observed Seismic Response - produces – stratigraphic layered Earth model – INVERSE modelling
How do you calculate impedance
Velocity x Density
Attenuation is
amplitude loss
frequency dependent attenuation
.
frequency independent attenuation
.
What is acoustic impedence inversion
The inversion of reflection seismograms into synthetic acoustic impedance sections
benefits of impedence data
(3) +1
rock properties don't tell gradational changes rock properties Impedance (Velocity x Density) is a rock property and not an interface property like reflectivity Wavelet complexity such as tuning is diminished such that interfaces become simpler Acoustic impedance volumes incorporate the gradational changes in rock properties not imaged by seismic reflectivity i.e. focuses attention on layer variations Acoustic impedance is closely related to rock properties of interest such as lithology, porosity and pore fluid fill – we relate them via empirical relationships
two different types of impedence inversion algorithms
trace based
model based
How to measure Q
capture wavelet at two points on a colinear path, use the difference to calculate Q
