Introduction to Petroleum Geology

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Geology (GLGY 577-UCAL) Midterm Exam

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Question 1

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

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

Question 2

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 reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates.
C	Natural gas produced from reservoir rocks that are interbeded with alternating permeable and non-permeable layers.
D	Natural gas produced from reservoirs that are under very high pressures making it tight and easier to extract.

Question 3

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

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

Question 4

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

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

Question 5

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

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

Question 6

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

Question 7

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

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

Question 8

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

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

Question 9

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

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

Question 10

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

Question 10 Explanation: 

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

Question 11

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

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

Question 12

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

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

Question 13

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

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

Question 14

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

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

Question 15

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

Question 16

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

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

Question 17

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

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

Question 18

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

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

Question 19

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

Question 20

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

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

Question 21

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

A	Rmc
B	Ro
C	Rm
D	Rt
E	Rw

Question 22

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

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

Question 23

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

A	0.09
B	0.08
C	1.08
D	0.65
E	1.00

Question 23 Explanation: 

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

Question 24

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

Question 25

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

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

Question 26

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	Well diversion trajectory angles.
D	Porosity and permeability of the core.

Question 27

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

Question 27 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.

Question 28

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 limit of the lower boundary (red line above) and So maximum is obtained from the upper boundary (green line above).
B	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).
C	You cannot take these measurements from a Pickett Plot. You must use a well log to determine such properties.
D	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).
E	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).

Question 29

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

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

Question 30

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

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

Question 31

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

A	Exploration
B	Development
C	Reserves Growth
D	Appraisal
E	Production

Question 31 Explanation: 

This is supposed to be an easy question.

Question 32

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

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

Question 32 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 33

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

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

Question 34

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

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

Question 34 Explanation: 

R_H = 1/C_H

Question 35

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	It measures the true density of the material.
C	Typically, silicon has a higher neutron reading than carbon.
D	A typical tool uses uranium as the energy source.
E	The thermal phase of the tool uses energy at around 10 eV

Question 36

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

Question 37

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

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

Question 38

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

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

Question 39

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	~ 3.50
D	~ 0.20
E	~ 4.00

Question 39 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 40

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

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

Question 41

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

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

Question 42

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	~ 0.20
C	~ 1.76
D	~ 0.71
E	~ 2.81

Question 42 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 43

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

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

Question 44

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

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

Question 45

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

Question 46

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 47

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 where common petroleum system characteristics exists, while the prospect is an area where the hydrocarbons can be extracted economically.
C	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.
D	The play is an area of interest for petroleum exploration and a prospect is the lowest point on the trap which can hold petroleum.
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 48

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

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

Question 49

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

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

Question 50

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

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

Question 51

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

Question 51 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 52

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

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

Question 53

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

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

Question 53 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 54

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

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

Question 55

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

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

Question 56

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

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

Question 57

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

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

Question 58

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

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

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