FESTNINGEN - PART 2
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Sedimentological and petrophysical logging
Svalex:
Locality: Festningen – Part 2: Sedimentology and petrophysics exercise.
34/10-14
22.03.01 11:41:17
0.
6.
6.
GR (API)
CALI (inch)
BS (UNKNOWN)
DEPTH
100. M 0.2
16.
0.2
16.
0.2
0.2
0.2
LLD (ohm.m)
ILD (ohm.m)
LLS (ohm.m)
MSFL (ohm.m)
RT (UNKNOWN)
20. 1.95
20. 0.45
20. -0.75
20. 0.4
RHOB (gm/cc)
NPHI (dec)
DRHO (gm/cc)
PHIF (UNKNOWN)
DT (uSec/ft)
SAND (UNKNOWN)
2.95 140.
40. 4.
0.
KLH ()
0.01
20000.
SW ()
0.25
1.
0.
-0.15
-0.2
20.
1:100
1925
Typical geological sedimentological log with legend (left) and petrophysical log (right) (Not from the same
interval). Note the grain size scale at the bottom of the lithological log.
1. Learning Goals:
1. Show how petrophysical logs illustrate changes in sedimentology, rock types and fluid types.
2. Make a visual and mental connection between rock properties as you can see them in nature and how
they will appear on petrophysical well logs like neutron, density, gamma ray, resistivity and acoustic.
2. Topics to be presented in the field:
3. Sedimentological part: Make a sedimentology log.
4. Back on the ship: Petrophysics part: Make petrophysical logs from the sedimentological log. The logs
must be readable from 10 meters distance
3. Questions to be answered:
Geology:
5. Make a sedimentological log profile through the formation given to you – often this is Geer Vally
formation at Festningen (Alternatives to Geer vally is Ymerbukta or the Festningen sandstone area).
Start and end points and fluid contacts in the formations will be given. Typically what goes into such a
log is lithology types, grain sizes, thicknesses, sedimentary structures, facies types, fossils.
6. Also keep in mind that you shall use this information as basis for drawing petrophysical logs.
File: Case_Festningen_Part-2_Petrophysics_Sedimentology_Ver-8.docx
FESTNINGEN - PART 2
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Sedimentological and petrophysical logging
Petrophysics:
7. Back on the ship: Construct petrophysical logs from the observations you make in the field. Try to
illustrate trends in the data like upward fining/coarsening, sorting etc. Normally what you do in an oil
company is the opposite – you go from logs to rock properties. This exercise trains your mind in
relating rocks to log response.
8. Try to evaluate from your knowledge of the logging tools how thin layers the different tools may see. A
section of thin oil bearing layers in between shale layers – how will they look on the logs? Use the
group competence and find out how different logs would look in the observed formations. If you lack
competence in some field, you can ask the consultants (teachers) present or other groups for assistance.
If thin layer shale-sand-zones with oil are interpreted to be too shaly – while they are not – you may lose
a lot of producible hydrocarbons… How can you identify such zones? What kinds of logs may be
needed?
a. Gamma log
b. Resistivity logs – micro log and deep resistivity. The fluid contacts will be shown in the field. Evaluate
on the basis of grain size and sorting how the response will be in the different formations e.g. within an
oil zone. Is there any influence from grain size and sorting on the resistivity response in an oil zone?
Will the water saturation be influenced?
c. Acoustic log (sonic)
d. Density log. Make sure to show changes in grain, pore and fluid properties.
e. Neutron porosity log (May be of special interest in any gas zone – as a gas indicator) Make sure to
show changes in grain, pore and fluid properties.
f. The FMI image log takes 192 sample for each mm of depth. The other logs takes one sample per 15 or
30 cm. How thin layers may an image log find – given that that each measurement electrode has a
diameter of about 1 cm?
All logs are to be drawn at a scale of 1:50. You have to find out how many points – “measurements” – you want to
make per meter.
9. Find N/G (Net to gross ratio shows how large fraction of producible reservoir you have got out of the
total rock volume )
Geophysics.
10. Is it possible to see productive reservoir bodies on the seismic sections in this area?
Drilling:
11. Understanding the geology and log responses: How can these help you to do a better job in your field of
study?
Production:
12. Understanding the geology and log responses: How can these help you to do a better job in your field of
study?
Reservoir engineering:
13. Understanding the geology and log responses: How can this help you to do a better job in your field of
study?
Presentation of results:
14. Two groups will be asked to give a presentations of 4 minutes each of their logs in plenum on the ship.
Make the logs large enough to be seen at 10 meters distance.
You bring: Pencil, rock magnifying lens, meter measure, notebook. The grain size estimates are to be
qualitative…
Responsible teachers: Sverre Ola Johnsen, Mathias Lundmark (geology), Helge Langeland (petrophysics)
File: Case_Festningen_Part-2_Petrophysics_Sedimentology_Ver-8.docx