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

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

Question 2

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

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

Question 3

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

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

Question 4

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	Average grain size and grain size sorting.
C	Both amount of porosity and type of lithology.
D	Magnitudes of both porosity and permeability.

Question 5

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

A	19
B	44
C	-2
D	10
E	12

Question 6

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	Rmc, Rxo, Ri, Rt
C	Rm, Rmc, Ri, Rw
D	Rxo, Rs, Rm, Rmc
E	Rxo, Rmc, Rm, Ri

Question 7

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

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

Question 8

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

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

Question 9

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

A	0.08
B	1.00
C	1.08
D	0.65
E	0.09

Question 10

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. = 15 m and D.I. = 5 m
C	Vert. Res. = 2 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 11

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

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

Question 12

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

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

Question 13

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

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

Question 13 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.

Question 14

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

Question 15

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

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

Question 16

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

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

Question 17

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

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

Question 18

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

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

Question 19

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

Question 20

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

Question 21

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

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

Question 22

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

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

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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.