3. Petrophysical applications/3
Abundant dark
conductive patches
interpreted as vuggy
porosity. There is
likely to be good
connectivity in this
example. The bright,
resistive patches are
probably bioclasts.
Porosity typing
4. Petrophysical applications/4
Alternating relatively resistive
and conductive horizons
corresponding to fining-upward
units. Conductive horizons are
the coarser, more porous
packstone-grainstone facies.
Resistive horizons are finer
grained packstone to
wackestone facies.
Permeability heterogeneity
Well laminated horizon
8. Petrophysical applications/8
Static and dynamic
UBI images of deep
marine sandstones
Non-planar feature -
this represents
sandstone remobilised
during dewatering
Net sand
9. Petrophysical applications/10
• What is thick and thin?
• Thin beds & their effect on open hole logs
… or lack of …
• Considerations such as the earth model
where images and core can help
Thin beds
10. Petrophysical applications/11
• What is thick or thin?
• “something that is thinner than the
measurement resolution.”
What is resolution?
Depends who asks?
Geophysicist, geologist, petrophysicist?
Definitions
11. Petrophysical applications/12
Scales of data
Borehole
images
and
dipmeters
15
m
1
cm
Core
10000
100
1
0.01
3D seismic
0.01
1
100
10000
Fault throw (m)
Cumulative
fault
density
(faults
per
km)
Walsh, Watterson
& Yielding 1991
12. Petrophysical applications/13
• Vertical resolution - logging tool
“Thinnest bed in which a true reading can be obtained.”
- bit vague?
Log resolution
• Intrinsic vertical resolution (IVR)
“Width of the tool response
function at half its maximum value.”
“thinnest average bed that can
be distinguished from its
neighbours and responds to
>90% true bed value”
15. Petrophysical applications/16
• Do Standard log measurements
underestimate net pay?
Wireline logs
This is a resolution problem
100 sw 0
The problem
16. Petrophysical applications/17
• Bypassed pay estimation STOIIP or gas
equivalent?
• More accurate reservoir delineation &
producibility perm/thickness (kh)?
• More accurate perforation & testing?
YES!
Does it matter?
17. Petrophysical applications/18
• Do cuttings show pay?
• ‘Spiky’ open hole logs that repeat?
• Vertical facies associations?
• May require tools below standard log
resolution to answer.
– core, image logs, dipmeters
Do we realise we have thin beds?
18. Petrophysical applications/19
• Understand the Geology ( the ‘earth model’)
• Enhance logs using the earth model
Use forward & inverse modelling to better
predict log responses
Adjust Porosity, Rt, Rxo, Sw, Vsh
=> STOIIP
Addressing the problem
29. Petrophysical applications/30
Horizontal or dipping?
Layer cake or injected sands?
Permeability - invasion?
Can lead to complex 2d/3d earth models.
Geological considerations
39. Petrophysical applications/40
High resolution images help us to build the all
important earth model, leading to:
– By passed pay estimation STOIIP?
– Reservoir delineation & producibility
permeability/thickness (Kh)
– Accurate perforation & testing improved
Looking at thin beds
40. Petrophysical applications/41
• Data Acquisition
• Existing tools
• High resolution tools
• Resolution Enhancement
• deconvolution, dual detector, squaring
• Formation Evaluation
• should be same as normal evaluation
Looking at thin beds
61. Petrophysical applications/63
• <2.5 ft Rt and Sw
• <1 ft porosity and lithology
• <3” shaliness
• Use core/image to calibrate at early stage
With thin bed modelling