Petrophysical Techniques

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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 I | Well Log Interpretation

Geology (GLGY 449-UCAL) Midterm II

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Question 1

Which of the following is a basic assumption underlying Archie’s equations as applied to sands or sandstone hydrocarbon reservoirs? (ID-P02-04)

A	Clay minerals are only present as discrete laminae.
B	Pressure gradient in the reservoir is the same above and below the oil-water contact.
C	Porosity in the reservoir is the same above and below the oil-water contact.
D	Clay-bearing shale laminae act as insulators between sand layers.
E	Salinity of formation water is the same above and below the oil-water contact.

Question 2

When using NMR, the mercury injection method is used for calculating what purpose? (ID-P02-13)

A	To measure pore throat radii.
B	For evaluating the effective porosity by separating unconnected porous space.
C	To measure water content and saturation in order to identify hydrocarbon bearing zones.
D	To measure permeability and porosity.

Question 3

In petrophysics, why would two Scientists looking at the same log may have two completely different conclusions? (ID-P02-12)

A	Because logging tools are often incarcerate hence interpretation is needed to correct tool errors using core driven data sources.
B	Because logging data have to be correlated with data from several other sources including physical core samples to obtain a near certain or certain conclusions.
C	Because petrophysics is not a cience.
D	Because petrophysics is heavily depend on unknown data sets.
E	Because logging data have to be correlated to with core samples to to obtain a near certain or certain conclusions.

Question 4

Why do standard dipmeter tools require water-based mud? (ID-P02-14)

A	To cool down the tool otherwise would be heated due to friction.
B	To allow electrons from the formations to flow though to the sensor.
C	The hydrogen in water reduces unwanted log responses.
D	To improve responses between electrodes.

Question 5

What are approximate vertical resolution and depth of investigation of the MSFL, respectively? (ID-P02-19)

A	Vert. Res. = 40 m and D.I. = 1.5 m
B	Vert. Res. = 2 m and D.I. = 5 m
C	Vert. Res. = 15 m and D.I. = 5 m
D	Vert. Res. = 5 m and D.I. = 10 m
E	Vert. Res. = 2.5 m and D.I. = 1.6 m

Question 6

When using nuclear magnetic resonance (NMR) tools, which of the following would have the greatest influence on relaxation time, T₂, of protons? (ID-P02-11)

A	Pore size distribution and pore fluid type.
B	Magnitudes of both porosity and permeability.
C	Both amount of porosity and type of lithology.
D	Average grain size and grain size sorting.

Question 7

High permeability reservoir rocks will have which of the following properties? (ID-P02-05)

A	Low value of bulk density.
B	High value of porosity exponent.
C	High value of oil saturation.
D	Low value of Formation Factor.

Question 8

Which of the following porosity modifiers will have the greatest effect on porosity calculated? (ID-P02-10)

A	Clay mineral cement.
B	Quartz cement.
C	Pore filling plagioclase feldspar.
D	Cal mineral lamination.

Question 9

Volumetric flow rate directly proportional to what other variable or condition? (ID-P02-01)

A	Cross sectional area and the height of the fluid column.
B	Cross sectional area.
C	The rate of flow, q.
D	Height of the fluid column.

Question 10

On the following profile of tool-measured resistivities away from the borehole with saline formation water relative to the drilling mud, what is labeled from 1 to 4? Answer is in respective order. (ID-P02-21)

A	Rmc, Ri, Ro, Rt
B	Rxo, Rs, Rm, Rmc
C	Rm, Rmc, Ri, Rw
D	Rmc, Rxo, Ri, Rt
E	Rxo, Rmc, Rm, Ri

Question 11

You observe an Gamma Ray response of API between 800 to 850 on a logging output. This type of response is typically associated with what rock type/lithology? (ID-P02-15)

A	Quartz or calcite-rich
B	Shale or shale-rich
C	Granite or basalt
D	Coals or coal-rich
E	Sandstone or sand-rich

Question 12

Which of the following is the most important fluid property affecting permeability? (ID-P02-03)

A	Dynamic viscosity
B	Salinity gradient
C	Fluid composition
D	Pore geometry

Question 13

Calculate Sw using the data obtained from following interpreted Pickett Plot. (ID-P02-17)

A	0.08
B	1.08
C	0.65
D	0.09
E	1.00

Question 14

Typically Quartz-rich zones will produce about ____ neutron porosity response on a well log. (ID-P02-16)

A	10
B	12
C	19
D	-2
E	44

Question 15

What are approximate vertical resolution and depth of investigation of the ILd, respectively? (ID-P02-02)

A	Vert. Res. = 0.6 m and D.I. = 2.5 m
B	Vert. Res. = 0.6m and D.I. = 1.6 m
C	Vert. Res. = 1 m and D.I. = 1.6 m
D	Vert. Res. = 2.5 m and D.I. = 1.6 m

Question 16

What are approximate vertical resolution and depth of investigation of the ILd, respectively? (ID-P02-09)

A	Vert. Res. = 1 cm and D.I. = 1.6 cm
B	Vert. Res. = 20 cm and D.I. = 30 cm
C	Vert. Res. = 1 cm and D.I. = 5 cm
D	Vert. Res. = 40 m and D.I. = 1.2 m
E	Vert. Res. = 5 cm and D.I. = 10 cm

Question 17

Which of the following is the main assumption underlying Archie’s equation? (ID-P02-06)

A	Oil and gas act as insulators within the formation.
B	Formation is clean and clay free both above and below the oil-water contact.
C	Porosity in the reservoir is the same above and below the oil-water contact.
D	Salinity of formation water is the same above and below the oil-water contact.
E	Porosity type is same above and below the oil-water contact.

Question 18

What would happen if you treat a hydrocarbon-bearing shale sand as clean? (ID-P02-08)

A	Oil saturation and water saturation will be underestimated.
B	Water saturation will be underestimated.
C	Vertical resistivity will be overestimated.
D	Oil saturation and water saturation will be overestimated.
E	Oil saturation will be underestimated.

Question 19

On the following profile of tool-measured resistivities away from the borehole with saline formation water relative to the drilling mud, where is the invaded zone? (ID-P02-22)

A	Section 2
B	Section 4
C	Within the borehole
D	Section 1
E	Section 3

Question 20

What is the effect of clay mineral conductivity on Ro if the formation water is characterized by moderate to high salinity? (ID-P02-18)

A	This will depend on the volume and type of clay minerals.
B	Ro will increase with increasing porosity.
C	Ro will crease with increasing oil saturation (So).
D	Ro will be relatively constant.

Question 21

Which of the following property best reflects a high-permeability reservoir rock for a given formation water? (ID-P02-20)

A	High value of porosity exponent (m).
B	Low value of bulk density.
C	High value of oil saturation (So).
D	None of the listed answers are correct.
E	Low value of the formation factor (F).

Question 22

Which of the following region is closest to the borehole? (ID-P02-07)

A	Invaded zone.
B	Virgin formation.
C	Flushed zone.
D	Mud build up.

Question 22 Explanation: 

There is no such thing called, "mud build up". If one of the given choices was "Mud cake", then it would be the correct answer. The next closest one is Flushed zone.

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Credits: Based on the excellent class notes provided by, Dr. Rudi Meyer during Fall 2014.
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Since most well log images and other materials are copyrighted, I cannot use them on my quizzes. Therefore, no well logs can be found in the following quiz. For the exam, you are expected to be able to interpret well logs. If you are a company or an organization willing to donate copies of well logs, please contact me. I really appreciate your contributions.