Introduction to Petroleum Geology

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Geology (GLGY 577-UCAL) Midterm Exam

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Question 1

Most neutron tools use which of the following? (ID-PGL-16)

A	Uranium source
B	Thermal phase of the scatter
C	Epi-thermal phase of the scatter
D	Electric energy

Question 2

Which of the following frequency can be used in conduction resistivity measurements? (ID-PGL-21)

A	20 MHz
B	2 kHz
C	2 MHz
D	100 kHz
E	200 Hz

Question 3

Typically which data source would provide the largest area coverage? (ID-PGL-46)

A	3D seismic
B	2D seismic
C	4C seismic
D	4D seismic

Question 4

Which of the following drilling mud has the lowest impact on the environment? (ID-PGL-12)

A	Denial-based mud
B	Oil-based mud
C	Acids-based mud
D	Synthetic mud

Question 5

Typically, what is the depth of investigation for deep induction tools (ILd)? (ID-PGL-30)

A	1 - 5 m
B	2 - 3 m
C	0.5 - 1.5 m
D	0.5 - 2m
E	0.8 - 1.5 m

Question 6

What is the depth of investigation for the deep lateral resistivity log? (ID-PGL-17)

A	~ 1.1 to 2 m
B	~ 26 to 30 cm
C	~30 to 50 cm
D	~ 1.35 to 1.75 m
E	~ 1.2 to 1.25 m

Question 7

Which of the following environment would you expect to find most trace fossils? (ID-PGL-40)

A	Point bars
B	Deep marine
C	Beach marine
D	Tidal flats

Question 8

Which of the following fraction has the highest number of carbons per molecule (highest boiling point)? (ID-PGL-05)

A	Lubricating oil
B	Heavy gas oil
C	Residuum
D	Diesel fuel
E	Kerosene
F	Gasoline

Question 9

Which of the following combination most likely result in formation of crude oil during diagenesis? (ID-PGL-02)

A	Carbohydrates, Proteins and Lipids
B	Proteins and Lipids
C	Carbohydrates and Proteins
D	Proteins and Lignin
E	Lignin and Carbohydrates
F	Lignin, Carbohydrates, Proteins and Lipids

Question 10

The Caesium-137 is commonly used as the source for which of the following well logging tools? (ID-PGL-39)

A	Neutron tools
B	Density tools
C	Gamma Ray tools
D	Resistivity tools

Question 11

Typically when interpreting wireline well logs, the sand zones will produce _____ Gamma Ray (GR) readings, shale zones will produce _____ Gamma Ray (GR) readings and the threshold value for differentiating between sand and shale is ___. (ID-PGL-14)

A	high , low , at 75 API
B	low , high , arbitrary
C	low , high , at 75 API
D	high , low , at 15 API
E	low , high , at 15 API
F	high , low , arbitrary

Question 12

If you have multiple possibilities for the line of Ro on the Pickett Plot, what is the best approach for obtaining Sw? (ID-PGL-25)

A	Calibrate the Ro line with the core or well logs.
B	Generate the most two extreme Ro lines on the Pickett Plot with the maximum Rt and minimum Rt as your reference bounds.
C	Generate several parallel Ro lines on the Pickett Plot.
D	Generate several Ro lines on the Pickett Plot.
E	Use the Ro line that is most centered to the all other Ro lines.

Question 13

The F factor becomes extremely difficult to obtain when... (ID-PGL-26)

A	...the formation is low in clay minerals.
B	...the formation is composed of highly complex pore structures.
C	...the formation is saturated with fresh water.
D	...the formation is concentrated with clay minerals in saline waters.

Question 14

Typically, what is the vertical resolution of Gamma Ray logs? (ID-PGL-38)

A	~ 80 cm
B	~ 40 cm
C	~ 10 cm
D	~ 30 cm

Question 15

Calculate the sand:shale for the interval between 1000 m and 5000 m on the following Gamma Ray (GR) curve. Assume a sand cut-off of 75 API. (ID-PGL-56)

A	~ 3.50
B	~ 2.81
C	~ 0.71
D	~ 1.76
E	~ 0.20

Question 15 Explanation: 

Net sand interval = 3550 m - 1000 m = 2550 m (read off the GR curve)
Net shale interval = 5000 m - 3550 m = 1450 m (read off the GR curve)
Hence, sand:shale = 2550 m/1450 m = 1.7586...

Question 16

Which of the following is true about cementation factor, m? (ID-PGL-24)

A	All or other things being equal, as m increases, the prore geometry become complicated.
B	All or other things being equal, increase in m will result in decrease in a.
C	All or other things being equal, increase in m will result in increase in formation factor, F.
D	Value of m is independent of the surface area of the pores.
E	The m and porosity are directly related to each other.

Question 17

Ideal diagenesis of organic matter will result in... (ID-PGL-04)

A	reservoir.
B	hydrocarbons.
C	kerogen.
D	traps.
E	carbon-oxygen chains.

Question 18

The following is a map section created using the Canadian Dominion Land Survey (DLS) method. What is the location number for the X position? (ID-PGL-43)

A	Section 5
B	Section 4
C	Section 3
D	Section 9
E	Section 10

Question 19

Typically what would you expect to observe on shale conductivity? (ID-PGL-32)

A	Increase with sand interbedding.
B	Decrease with increase in clay interbedding.
C	Decrease with depth.
D	Decrease with increase in hydrocarbon saturation.
E	Becomes almost zero with hydrocarbon saturation.

Question 20

Which of the following statement is true about the neutron wireline tool? (ID-PGL-15)

A	It measures the slow-down length of neutrons when they interacts with atoms.
B	A typical tool uses uranium as the energy source.
C	Typically, silicon has a higher neutron reading than carbon.
D	The thermal phase of the tool uses energy at around 10 eV
E	It measures the true density of the material.

Question 21

Which of the following geophysical data is cheapest to run? (ID-PGL-50)

A	3D seismic data acquisition
B	4D seismic data acquisition
C	Crosswell seismic data acquisition
D	2D seismic data acquisition

Question 22

Fossil fuels are chains of... (ID-PGL-01)

A	carbon-oxygen bonds.
B	carbon-hydrogen bonds.
C	transitional metals and carbons.
D	kerogen.
E	inorganic compounds.

Question 23

Seimic data are difficult to obtain when.... (ID-PGL-48)

A	the beds has no dip, hence almost horizontal.
B	there are multiple sleeply dippinng beds.
C	the seismic signals have to travel through fluids (eg. oceanic seismic).
D	the beds are extremly thick.

Question 24

Which of the following is true (scientifically) regrading fracking? (ID-PGL-37)

A	It will not affect aquifers.
B	It is easier to frack on soft sediments.
C	It is a relatively very new technology.
D	It may result in earthquakes.

Question 25

Which of the following property would adversely effect measurements and operation of well logging tool? (ID-PGL-28)

A	High concentration of formation fluids.
B	Low viscosity mud.
C	Low mud invasion zone.
D	Directionally focused tools.

Question 25 Explanation: 

Low viscosity mud have two major problems. It may not be able to counteract the formation pressures. Secondly, it will most likely penetrate deep into the formation where formation pressures is too low. Most drilling mud are neither high viscous nor low viscous.

Question 26

Calculate Sw using the data obtained from following interpreted Pickett Plot. (ID-PGL-58)

A	1.08
B	0.65
C	1.00
D	0.09
E	0.08

Question 26 Explanation: 

Sw = (Ro/Rt)^(1/2) = (0.6/70)^(1/2) = 0.09258....

Question 27

The best resistivity data used for identification of lithology are obtained from which of the following? (ID-PGL-27)

A	Rmc
B	Rw
C	Rm
D	Ro
E	Rt

Question 28

Which of the following formation factor most likley represent a rock that contains almost all fuild? (ID-PGL-18)

A	F = 0.2
B	F = 0.7
C	F = 0.9
D	F = 2.2
E	F = 0.5

Question 29

How would you obtain Rw and So maximum from a Pickett Plot? You may use the following diagram to answer this question. (ID-PGL-57)

A	Rw is obtained from the upper boundary (green line above) and the Sw is obtained from the upper limit of the lower boundary (red line above).
B	So maximum is the intersect point between the lower boundary (green line above) and read off the x-values straight down (first brown dash line down). The Rw is the x-value of the upper most point and read off the x-axis (second brown dash line).
C	You cannot take these measurements from a Pickett Plot. You must use a well log to determine such properties.
D	Rw is the intersect point between the lower boundary (green line above) and read off the x-values straight down (first brown dash line down). The So maximum is the x-value of the upper most point and read off the x-axis (second brown dash line).
E	Rw is obtained from the upper limit of the lower boundary (red line above) and So maximum is obtained from the upper boundary (green line above).

Question 30

Given C_H = 0.102 what is the R_H? (ID-PGL-20)

A	102.0 Ωm
B	9.80 Ωm
C	120.0 Ωm
D	0.102 Ωm

Question 30 Explanation: 

R_H = 1/C_H

Question 31

Which of the following is true? (ID-PGL-44)

A	Computer algorithms for reservoir characterization models heavily depends on the analytical variables as opposed to empirical variables.
B	In Alberta, we commonly find oil-wet rocks in the subsurface.
C	Typically, as you move closer to mountains, frequency of structural traps increases.
D	Typically, as you move closer to mountains, frequency of stratigraphic traps increases.
E	In Alberta, lens traps are the most common type of hydrocarbon traps.

Question 32

Which of the following condition would increase the invasion of drilling mud filtrate? (ID-PGL-45)

A	Very high permeability in the formation.
B	Very high formation pressures.
C	Very high porosity in the formation.
D	Very low formation pressures.

Question 33

Fining upwards sequence is associated with which of the depositional history? (ID-PGL-54)

A	Deep marine sediments
B	Fluvial point bar deposits
C	Progradating marine shelf
D	Progradating delta deposits

Question 34

Tortuosity factor... (ID-PGL-31)

A	is highly dependent on the formation factor.
B	is directly proportional to the resistivity.
C	varies between 0.35 and 4.5.
D	is most commonly found to be equals to 1.0.

Question 35

What is the difference between a play and a prospect? (ID-PGL-08)

A	None of these answers are correct.
B	The play is an area of interest for petroleum exploration and a prospect is the lowest point on the trap which can hold petroleum.
C	The play is an area where common petroleum system characteristics exists, while the prospect is an area where the hydrocarbons can be extracted economically.
D	The play is an area of interest for petroleum exploration while the prospect is an area within a play that is expected to produce hydrocarbons.
E	The play is a large area where hydrocarbons may be found, while the prospect is an area where there is a current production in hydrocarbons.

Question 36

Which of the following is the most problematic issue with picking a wrong datum? (ID-PGL-51)

A	The calculated net sand volume may be incorrect.
B	The overall assessment of the geology may be completely wrong.
C	The obvious features of the well logs may be ignored.
D	The key well logs features may not be able to correlate further away from the reference wells.
E	The topography of the area may be distorted.

Question 37

What is the first step in petroleum systems "value chain"? (ID-PGL-07)

A	Development
B	Reserves Growth
C	Production
D	Appraisal
E	Exploration

Question 37 Explanation: 

This is supposed to be an easy question.

Question 38

Typically, what is the resolution thickness of deep dual induction tools (ILd)? (ID-PGL-29)

A	~ 50 cm
B	~ 1.5 m
C	~ 3 m
D	~ 2.5 m
E	~ 80 cm

Question 39

Thin areas on isopach maps are indicative of which of the following characteristic? (ID-PGL-42)

A	High net pay regions
B	Low net pay regions
C	High concentration of hydrocarbons
D	Hills or mountains
E	Valleys

Question 40

What is tight gas? (ID-PGL-10)

A	Natural gas produced from reservoirs after the peak production of the play. In other words, low yield gas produced after production has been in place for a period of time.
B	Natural gas produced from reservoirs that are under very high pressures making it tight and easier to extract.
C	Natural gas produced from reservoir rocks that are interbeded with alternating permeable and non-permeable layers.
D	Natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates.

Question 41

Regardless of the scale, what can you derive from the following gamma ray (GR) signature? (ID-PGL-49)

A	Coarsening downward sequence
B	Very high gamma ray kick Hint: You need the scale for this interpretation.
C	Coarsening upward sequence
D	Net sand content Hint: You need the scale for this calculation.

Question 42

Which of the following has the best verticale resolution? (ID-PGL-47)

A	Gamma ray log
B	Caliper log
C	Sonic log
D	Dipmeter log
E	Neuron log

Question 43

Which of the following statement is true about fromation factor, F? (ID-PGL-23)

A	Porosity and formation factor is directly related to each other.
B	Pore stucture is directly related to the formation factor.
C	Formation factor is inversly related to tourtousity factor.
D	Clean granular formations have a lower formation factor than clean carbonate formations.

Question 44

As resistivity ____ the conductivity ____. Answers are in respective order. (ID-PGL-19)

A	increase , increase
B	increases , decrease
C	They are not related to each other.
D	decarses , decrease

Question 45

At what stage during the natural formation of crude oil the cracking take place? (ID-PGL-03)

A	Zone of gas formation
B	Catagenesis
C	Diagenesis
D	Unaltered organic matter
E	Initial burial

Question 46

Which of the following is not an assumption used in Archie equation? (ID-PGL-22)

A	Resistivity of the formation water is same above and below the contact.
B	Proposity must be the same both above and below the oil-water contect.
C	Formation is completely saturacted with fulids.
D	Formation must be clean and free of clay.
E	Oil and gas acts as conduits for electrical signals.

Question 47

Knowing that it is a stratigraphic trap, what is represented by diagram E? (ID-PGL-06)

A	Pinchout trap
B	Fault trap
C	Lens trap
D	Salt dome trap
E	Unconformity trap
F	Anticline trap

Question 48

Generally what is the reference elevation for core samples taken out of a drilling operation? (ID-PGL-11)

A	Lowest point of the hydrocarbon pool
B	Bottom of the major formation
C	Position of the Kelly Bushing
D	Highest point of the hydrocarbon pool
E	Top of the major formation

Question 49

What is the primary purpose of steam injection into a zone of crude oil? (ID-PGL-09)

A	It will reduce viscosity of crude oil hence allowing it to be pumped.
B	Increase pressure within the chamber hence driving the crude oil out of the system.
C	Decrease friction between the pore walls and the crude oil.
D	Increase pressure within the chamber which facilitate extraction.
E	Increase the conductivity between pores.

Question 50

Why would you choose metal casings as opposed to mud casings for top sections of the wells? (ID-PGL-36)

A	To reduce fractures near the neck.
B	To prevent well blowouts.
C	To protect aquifers from contamination.
D	To provide support for the Kelly Bushing.

Question 50 Explanation: 

Usually aquifers are situated close to the surface (relative to the deepest part of the well). Hence using mud may result in cross contamination.

Question 51

Neutron porosity, ΦN is measured to be 15% and the Density porosity, ΦD is measured to be 10% on a sandstone calibrated matrix. It is plotted on the Schlumberger CP-1e as shown below (red circles). What is the true porosity given there is no gas effect in this particular section? (ID-PGL-53)

A	10%
B	12%
C	15%
D	5%
E	6%

Question 52

Which of the following provide the best analytical evidence for specific formation properties (eg. type of rock, porosity, etc)? (ID-PGL-13)

A	Seismic sections
B	Gravity readings
C	Core samples
D	Wireline well logs
E	Geostatistical models such as kriging

Question 53

On the following hypothetical geologic map, the black lines are strike lines. When drawing cross sections, the line in _____ can be used as a dip section plane, the line in _____ can be used as a strike section plane, and the line in ____ can be used as an oblique section plane. Answers are in respective order. (ID-PGL-52)

A	blue , orange , green
B	orange , green , blue
C	blue , green , orange
D	orange , blue , green
E	green , orange , blue
F	green , blue , orange

Question 54

Calculate the net:gross for the interval between 1000m and 5000m on the following Gamma Ray (GR) curve. Assume a sand cut-off of 75 API. (ID-PGL-55)

A	None of the answers are correct.
B	~ 0.64
C	~ 4.00
D	~ 3.50
E	~ 0.20

Question 54 Explanation: 

Gross thickness = 5000 m - 1000 m = 4000 m
Net sand interval = 3550 m - 1000 m = 2550 m (read off the GR curve)
Hence, net:gross = 2550 m/4000 m = 0.6375

Question 55

In order to correct the depth measurements of cores obtained from diverted or horizontal wells, you must obtain which of the following? (ID-PGL-35)

A	Length of the drill string.
B	Total length of the recovered core.
C	Porosity and permeability of the core.
D	Well diversion trajectory angles.

Question 56

Calculate the geothermal gradient given following information. (ID-PGL-33)
BHT (bottom hole temperature) = 255^o F
Surface temperature = 75^o F
Depth which BHT was measured: 11400 ft

A	~ 0.015oF/ft
B	~ 0.028oF/ft
C	~ 0.016oF/ft
D	~ 0.029oF/ft
E	~ 0.018oF/ft

Question 56 Explanation: 

Usually on exams, you will be required to read some of the values from a wireline well log.

Question 57

As a Petroleum Geologist, you often have to make decisions based on limited access to samples and data. Your boss sent you the following image of a core from an unknown location at an unknown depth. Just by looking at the image, which of the following statements would you submit to your boss? (ID-PGL-34)

A	This part of the core is most likely concentrated with bitumen.
B	This part of the core is most likely saturated with organic materials.
C	This part of the core is most likely harder and stronger relative to other areas of the core.
D	This part of the core is most likely have a very high permeability.
E	This part of the core is most likely have a very low permeability.
F	This part of the core is most likely saturated with hydrocarbons.

Question 57 Explanation: 

For this question, multiple answers are possible. You may choose the one with bitumen and hydrocarbons and argue that those answers are correct. However, on multiple choice exams you are expected to choose most suitable answer. Technically you cannot say this is hydrocarbons (HC) or bitumen because by definition, you must satisfy the chemical and physical properties of such materials in order to classify as such. But the term "organic materials" can be used for border range of things including HC and bitumen.

Question 58

Given following information, calculate Net:Gross and Sand:Shale values. (ID-PGL-41)
net sand = 15.5 m
shale = 5.3 m
gross thickness = 26.3 m

A	Net:Gross = 59 and Sand:Shale = 29
B	Net:Gross = 59 and Sand:Shale = 34
C	Net:Gross = 0.59 and Sand:Shale = 2.92
D	Net:Gross = 0.59 and Sand:Shale = 0.34
E	Net:Gross = 0.79 and Sand:Shale = 0.34

Question 58 Explanation: 

On the exam you will most likely be given a well log. You will have to calculate the above given values from the log. You should know how to read logs.

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