Petrophysical Techniques; Geology/Geophysics 449
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Questions on Petrophysical Log Interpretation will not appear in the following exam. Log questions are published under a separate section.
Go to: Midterm II | Well Log Interpretation
Geology (GLGY 449-UCAL) Midterm I
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Question 1 |
A | Very thin formation; |
B | Shale; |
C | Highly radioactive formation; |
D | Highly non-radio active formation; |
E | Coal; |
Question 2 |
A | ...the neutron radiation omitted by the formation nuclei. |
B | ...the radiation omitted by inelastic collisions between the neutron and the formation nuclei. |
C | ...the radiation that was not absorbed by the formation. |
D | ...the radiation omitted by elastic collisions between the neutron and the formation nuclei. |
Question 3 |
A | Fast mudcake buildup with very deep mud filtrate. |
B | It all depends on the type of mud used for the drilling process. |
C | Slow mudcake buildup with very shallow mud filtrate. |
D | Slow mudcake buildup with very deep mud filtrate. |
E | Fast mudcake buildup with very shallow mud filtrate. |
Question 4 |
A | The Well-I most likely surrounded by a lithology that is very porous and permeable than Well-II; hence faster mudcake build up have lead to smaller invaded zone. |
B | The Well-II most likely surrounded by a lithology that is very porous and permeable than Well-I; hence the faster mud flow resulted in a large invaded zone. |
C | The Well-I most likley surrounded by a lithology that poor in porosity and permeability than Well-II; hence faster mudcake build up have lead to smaller invaded zone. |
D | The Well-II most likley surrounded by a lithology that poor in porosity and permeability than Well-II; hence the faster mud flow resulted in a large invaded zone. |
Question 5 |
A | Thin mud film between the casing and the formation. |
B | Mudcake itself surrounding the borehole. |
C | Hydrostatic pressure of the formation. |
D | Lithostatic and hydrostatic pressure of the formation. |
E | Lithostatic pressure of the formation. |
Question 6 |
A | Carbonates |
B | Organic content poor shale |
C | Mudstone |
D | Black shale |
E | Clean coal |
F | Clean sand |
Question 7 |
A | As bulk density. |
B | As matrix density. |
C | As neutron density. |
D | As a difference between bulk and fluid density. |
E | As fluid density. |
Question 8 |
A | Caliper logs |
B | Neutron logs |
C | Gamma ray logs |
D | Spontaneous potential logs |
E | Density logs Hint: Nope, that's an indicator of porosity. |
Question 9 |
A | The density can be used to calculate porosity of formations. |
B | The density logs can be used to resolve extremely thin formations and transitional zones. |
C | A high log value of density indicates a very good reservoirs. |
D | It can help determine the type of drill bit to use to cut into the formations. |
E | It provides an overview of the lithological formations (for example, quartz from calcite). |
Question 10 |
A | About 15 minutes |
B | About a day |
C | About 4 hours |
D | About 10 hours |
E | About 2 years |
Question 11 |
A | ...a response close to the calibrated zero position. |
B | ...a very high positive response. |
C | ...a very low negative response. |
D | ...no response at all (at zero level). |
Question 12 |
A | It is dependent on what type of logging tool is used. |
B | It is that of the surface. |
C | It is that of the formation. |
D | It is that of the drilling mud. |
Question 13 |
A | ~ 15% |
B | ~ 45% |
C | ~ 35% |
D | ~ 5% |
E | ~ 20% |
Question 14 |
A | gradual increase in density |
B | sudden increase in density |
C | high natural radiation levels |
D | gas effect |
Question 15 |
A | Improved logging tools. |
B | Improved speeds of drilling. |
C | Improved cost efficiency (low cost). |
D | Improved logistics due to smaller equipment. |
E | Improved drill bits. |
Question 16 |
A | In the electronics bay. |
B | In the logging equipment casing. |
C | Outside of the borehole; in the data collection truck. |
D | In the bottom hole assembly |
E | Inside the equipment pads. |
Question 17 |
A | 30o to 50o Celsius per meter of depth. |
B | 20o to 30o Celsius per kilometer of depth. |
C | 20o to 30o Celsius per meter of depth. |
D | 30o to 50o Celsius per kilometer of depth. |
E | 15o to 50o Celsius per kilometer of depth. |
F | 15o to 25o Celsius per kilometer of depth. |
Question 18 |
A | 15 - 20 cm |
B | 25 - 35 cm |
C | 10 - 40 cm |
D | 40 - 50 cm |
E | 0 - 10 cm |
Question 19 |
A | 35% |
B | 34% |
C | 3.0% |
D | 2.9% |
E | 29% |
porosity = (2.80 - 2.25) / (2.80 - 1.20) = 0.34 = 0.34%
Question 20 |
A | Higher formation porosity allowing more gamma rays to penetrate the formation. |
B | Lower formation density resulting fewer gamma rays being absorbed. |
C | Higher formation fluid content allowing gamma rays to penetrate the formation. |
D | Higher formation density resulting more gamma rays being absorbed. |
E | Higher radioactivity within the formation allowing gamma rays to interact with minerals within the formation. |
Question 21 |
(START) Dirty/used mud return to...
I. Distiller
II. Mud storage and settling tubs
III. Annulus spit out
IV. Desander
V. Shale shaker
VI. Mud pumps
A | V --> IV --> I --> II --> VI --> III |
B | III --> V --> I --> II --> VI --> V |
C | II --> V --> I --> III --> VI --> V |
D | I --> III --> VI --> IV --> V --> II |
E | I --> V --> VI --> II --> IV --> III |
F | I --> V --> IV --> II --> VI --> III |
Question 22 |
A | Spontaneous potential tools |
B | Neutron tools |
C | Caliper tools |
D | Density tools |
E | Gamma ray tools |
Question 23 |
A | ~ 65 o C |
B | ~ 43 o C |
C | ~ 55 o C |
D | ~ 49 o C |
E | ~ 45 o C |
Question 24 |
A | All-oil based mud because it is the cheapest and can overcome the environmental cleanup costs. |
B | Oil-based mud because oils do not react with evaporates and the mud can be formulated to not to react with subsurface formations. |
C | Synthetic-based mud because the mud can be engineered to be inactive with the evaporate formations and reduce the environmental impact. |
D | Water-based mud because it the most effective way to reduce the environmental impact. |
Question 25 |
A | Caliper logs |
B | Gamma ray logs |
C | Spontaneous potential logs |
D | Spectral gamma ray logs |
E | Density logs |
F | Neutron logs |
Question 26 |
A | No porosity loss within shale sequence due to shale being already compacted by the time of burial. |
B | Rapid loss of porosity within the sandstone sequence due to sandstone having higher permeability. |
C | Lower porosity loss in clay sequence compared to sandstone and shale due to clay being very dry in nature. |
D | Lower rate of porosity loss within the shale sequence due to tightly packed ionic bonds in shale. |
E | Increased rate of friction between clay particles due to overburden pressure. |
Question 27 |
A | The Na+ ion diffuse because it is much smaller in size than Cl-. |
B | The Cl- ion diffuse because Na+ attracts more water molecules. |
C | The Cl- ion diffuse because it has a stronger charge (attraction) than Na+. |
D | The Na+ ion diffuse because it has a stronger charge (attraction) than Cl-. |
E | The Na+ ion diffuse because Cl- attracts more water molecules. |
F | The Cl- ion diffuse because it is much smaller in size than Na+. |
Question 28 |
A | 10 - 15 cm |
B | 5 - 10 cm |
C | 20 - 30 cm |
D | 40 - 50 cm |
E | 60 - 70 cm |
Question 29 |
A | Very low density where fewer gamma rays are absorbed hence increasing the propagation distance. |
B | Low radioactive formations hence less destructive interference. |
C | Very high density allowing gamma rays to bounce off from atom to atom deep into the formation. |
D | High radioactive formations hence with more constructive interference. |
E | Formations that naturally produce very high rates of gamma rays hence allowing the artificial gamma rays to be amplified. |
Question 30 |
A | To allow cutting to be transported to the surface. |
B | To prevent mud filtrate from reaching inner parts of the formation of interest. |
C | To balance the hydrostatic pressure of the formation to prevent borehole collapses. |
D | To increase the speed of the drilling by applying pressure to the drill bit. |
E | To balance the lithostatic pressure of the formation to prevent borehole collapses. |
Question 31 |
A | Fractures of cements and minerals. |
B | Dissolution of early diagenetic cements. |
C | Break up of mineral compounds causing in situ porosity. |
D | Dissolution of grains at the grain to grain contact boundaries. |
Question 32 |
A | Use fracking to fracture the formations to increase permeability. |
B | Use horizontal drilling. |
C | Use high pressured drilling mud. |
D | Use larger boreholes and wider cutting tools. |
Question 33 |
Depth of Investigation: 15 -25 cm
Resolution: 50 cm
-Very high readings when shales or coals detected
A | Spontaneous Potential log |
B | Density log |
C | Neutron log |
D | Caliper log |
E | Gamma Ray or Special Gamma Ray long |
Question 34 |
A | 40 - 50 cm |
B | 5 -10 cm |
C | 20 - 30 cm |
D | 60 - 70 cm |
E | 10 - 15 cm |
Question 35 |
A | 25 - 30 cm |
B | 40 - 50 cm |
C | 0 - 10 cm |
D | 15 - 20 cm |
E | 30 - 35 cm |
Question 36 |
A | Analysis of grain volumes and grain characteristics of formation. |
B | Identification of non-radioactive clays and dolostones. |
C | Calculate the volume of shale to sand ratio. |
D | Calculate the bulk porosity of formation. |
E | Primary depth control. |
Question 37 |
A | Subsurface formation waters as trace substance. |
B | In radioactive natural deposits of uranium as a by product. |
C | In stable minerals such as phosphates. |
D | Within clay minerals such as illite and smectite. |
Question 38 |
A | ...the contrast between the nearby formations and the resolved formation is higher. |
B | ...the porosity and permeability of formations are higher. |
C | ...the radioactivity of the formations are much higher. |
D | ...the distance between formations are lower. |
E | ...the depth of investigation is much higher than expected hence increasing the vertical minimum bed resolution. |
Question 39 |
A | The invaded zone is larger in low porosity and permeability formations because slower flow result in slow build up of mudcake. |
B | The invaded zone is larger in high porosity and permeability formations because faster flow result in slow build up of mudcake. |
C | Larger invaded zones provides the best resolutions of LWD logs because it allow the waves/signals to be penetrated deep into the formation. |
D | The mid invasion is enhanced by the fast build up of mudcake. |
Question 40 |
A | Dissolution of early diagenetic cements |
B | Disintegration of minerals |
C | Organic activity |
D | Dissolution of cemented materials due to high temperature and pressure |
E | Fracture development |
Question 41 |
A | Porous formations filled with water. |
B | High vibrations caused by drilling tools. |
C | Porous formations filled with oil or gas. |
D | Fractures formed due to drilling itself (non-natural fractures). |
Question 42 |
A | Gamma rays do not react with any chemical components in the natural world. |
B | Gamma rays travel faster than other rays. |
C | Gamma rays are more penetrative than the others. |
D | Gamma rays produce a much higher energy difference that can be easily measurable by logging tools. |
E | Gamma rays are not naturally produced in the subsurface hence removes the uncertainty factor. |
Question 43 |
A | Compton scattering |
B | Radioactive capture |
C | Natural gamma rays |
D | Gamma ray bouncing effect |
E | Pair production |
Question 44 |
A | As basic solutions. |
B | As a part of hydrous minerals. |
C | In the chemical structures of clay. |
D | Within water molecules. |
E | As saline solutions. |
Question 45 |
A | clean limestones |
B | clean coal |
C | clean clay |
D | clean sandstones |
E | clean shale |
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End |
Credits: Based on the excellent class notes provided by, Dr. Rudi Meyer during Fall 2014.
FAQ | Report an Error
If you are a company or an organization willing to donate copies of well logs, please contact me. I really appreciate your contributions.
Type of tool |
DOI | Resolution | Used for… | Processes | Notes |
Caliper | NA | NA | -Borehole size and shape |
Spring loaded arms |
2 arm = diameter 4 arm = shape, orientation |
Gamma Ray |
10 – 15 cm | ~40 cm | -Lithology(vol. Shale/Sand often due to high K), geosteering, facies, depth control |
-Photoelectric effect (dom) -Compton scattering -Pair production -Scintillation counter + photomultiplier |
High (right kick): -Shale line -Organic content -K-Feldspars Low (left kick): -Clean sand -Carbonates -Clean coals |
Spectral Gamma Ray |
-Radioactive anomalies -Clay types -Volume of shale(clay) |
-Same as GR, but much better/larger scintillator | |||
Density & Photoelectric Factor |
< 10 cm | 11 – 40 cm | -Porosity, general lithology, min ids | ||
Neutron | 15 – 25 cm | ~50 cm | -Fluid, porosity, density, cross-over gas effect -Meassures porosity; used for calulating density |
Hydrogen | High (left kick): -Shales and coals Low (right kick): -Gas breaing fm./rocks Use Dphi & Nphi chart *Decreased with increased permeability |
Spontaneous Potential |
Depends | Depends | -Permeability(even small), lithology, facies, shale volume(not so much) |
Natural potential differences between fms. caused by: -Diffusion -Mambrane or shale potential |
Important: -Salinity of drilling fluid to fm. -Conductive drilling fluid -Constrasting permeability in adj. beds -Surface electrode(earth) No absolute scale(relatove +/-) Positive kick (relative): -Clean sand or sand stone, shaly sand Negative kick (relative): -Shale *Decreased with increased permeability |