Introduction to Petroleum Geology

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Geology (GLGY 577-UCAL) Midterm Exam

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Question 1

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

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

Question 2

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 = 2.2
D	F = 0.5
E	F = 0.2

Question 3

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

Question 4

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

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

Question 5

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

A	Development
B	Reserves Growth
C	Exploration
D	Appraisal
E	Production

Question 5 Explanation: 

This is supposed to be an easy question.

Question 6

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

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

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	Density tools
D	Gamma Ray tools

Question 8

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

A	0.09
B	1.08
C	0.08
D	1.00
E	0.65

Question 8 Explanation: 

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

Question 9

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

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

Question 10

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

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

Question 11

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 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 low permeability.
E	This part of the core is most likely concentrated with bitumen.
F	This part of the core is most likely saturated with hydrocarbons.

Question 11 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 12

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

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

Question 13

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

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

Question 14

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

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

Question 15

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

Question 16

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

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

Question 17

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

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

Question 18

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 18 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 19

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

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

Question 20

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

A	The play is an area where common petroleum system characteristics exists, while the prospect is an area where the hydrocarbons can be extracted economically.
B	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.
C	None of these answers are correct.
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 an area of interest for petroleum exploration and a prospect is the lowest point on the trap which can hold petroleum.

Question 21

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

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

Question 22

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 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).
B	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).
C	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).
D	You cannot take these measurements from a Pickett Plot. You must use a well log to determine such properties.
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 23

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

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

Question 24

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

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

Question 25

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

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

Question 26

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 27

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

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

Question 28

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 29

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

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

Question 30

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

Question 31

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

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

Question 31 Explanation: 

R_H = 1/C_H

Question 32

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

A	Rt
B	Rm
C	Rw
D	Rmc
E	Ro

Question 33

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

Question 34

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

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

Question 35

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

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

Question 36

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

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

Question 37

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

Question 37 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 38

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

Question 39

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

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

Question 40

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

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

Question 41

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

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

Question 42

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

Question 43

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

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

Question 44

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

Question 44 Explanation: 

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

Question 45

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

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

Question 46

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

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

Question 47

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

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

Question 48

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 directly proportional to the resistivity.
D	is highly dependent on the formation factor.

Question 49

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

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

Question 49 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 50

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

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

Question 51

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

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

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

Question 53

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

Question 53 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 54

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

Question 55

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

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

Question 56

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 56 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 57

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	10%
D	6%
E	5%

Question 58

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

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

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