Geology 14

What is the upper limit for the Poisson's ratio? (Hint- look at the formula for the Poisson's ratio) a. 1.0 b. 2.0 c. .5 d. .65 e. .35

.5

How many elastic constants does an isotropic medium have? a. 1 b. 2 c. 5 d. 9 e. 15

2

What is the maximum number of elastic constants for a material that is most anisotropic and obeys linearized relationship between the stress and the strain tensor? a. 5 b. 21 c. 36 d. 9 e. 81

21

Dry gas is defined as the one that contains: a. More than .1 gal/1000 ft3 of water vapor b. Less than .25 gal/1000 ft3 of water vapor c. Less than .3 gal/1000 ft3 of water vapor d. Less than .1 gal/1000 ft3 of water vapor e. More than .15 gal/1000 ft3 of water vapor

Less than .1 gal/1000 ft3 of water vapor

Out of the following, which one you would consider to be a dry gas? a. Ethane b. Butane c. Methane d. Isobutane e. Isopentane

Methane

The effective or equivalent anisotropic properties for a medium that is composed of thin isotropic horizontal layers and a set of oriented vertical fractures is a. Hexagonal b. Triclinic c. Orthorhombic d. Monoclinic e. Isotropic

Orthorhombic

Poststack seismic data are sensitive to the variations in: a. P-wave velocity b. S-wave velocity c. Density d. P-wave impedance (P-wave velocity times density) e. S-wave impedance (S-wave velocity times density)

P-wave impedance (P-wave velocity times density)

Magnetic method of geophysical exploration provides a quick and cost-effective way to delineate structural traps a. True b. False

True

The spontaneous potential (SP) and electric logs could be used in calculating the water saturation a. True b. False

True

Time-lapse or 4D seismology has gained popularity in recent years as allows detection of the movements of the subsurface fluids during production: a. True b. False

True

Electromagnetic (EM) methods of geophysical exploration are sensitive to the variations of which property of the subsurface? a. Density b. Seismic velocity c. Conductivity/Resistivity

Conductivity/Resistivity

What happens to the Poisson's ratio when a 100% brine saturated rock is replaced with 100% gas? a. Decreases b. Increases c. Stays about the same

Decreases

Gravity method of geophysical exploration is sensitive to the variations of what subsurface property? a. Electrical conductivity b. Seismic velocities and density c. Density d. Magnetic susceptibility e. Resistivity

Density

Gamma ray (GR) logs are typically used in discriminating between the sand and shale: a. True b. False

True

What is the meaning of a "stratigraphic unit" used in seismic sequence analysis? a. Strata of different rocks b. A given rock formation that is clearly visible on the seismic reflection records. c. A set of mutually intersecting rock formations visible on the seismic reflections. d. A relatively conformable succession of genetically related strata bounded at its top and base by unconformities

A relatively conformable succession of genetically related strata bounded at its top and base by unconformities

Isotherms are defined as the contours of constant temperature in the subsurface in general. It is observed that they are seldom horizontal. The reason for it is: a. Non-planar geometry of the sediments b. Movement of fluids c. Regional variations in heat flow d. A and B only e. A and C only f. A, B, and C

A, B, and C

Prestack seismic reflection amplitudes as a function of reflection angle are sensitive to the variations in: a. P-wave velocity b. S-wave velocity c. Density d. All of the above

All of the above

What are the criteria for commercial oil (hydrocarbon) accumulation? a. Existence of an organic rich source rock. b. Source rock must be sufficiently heated to yield petroleum c. There must be a reservoir with sufficient porosity and permeability to contain the hydrocarbon d. The reservoir must be seated by an impermeable rock to prevent the hydrocarbon from moving upward e. The source, reservoir, and the seal must be arranged such that the petroleum is trapped f. All of the above

All of the above

What is the primary objective of seismic sequence analysis? a. Interpret different sequence boundaries from seismic reflection data. b. Relate the sequence boundaries with the sedimentary history. c. Study how the basin was formed over the time. d. All of the above.

All of the above.

Both poststack and amplitude-variation with offset (AVO) inversion of seismic data provide a broadband (i.e. the low-frequency background trend and the high-frequency variations without any need for the background trends to be supplied from other information such as the well-logs and/or geology) a. True b. False

False

The gas-hydrates are composed mostly of ethane a. True b. False

False

Salinity of the subsurface water: a. Generally decreases with depth b. Stays nearly constant c. Generally increases with depth

Generally increases with depth

How the density of oil is generally expressed in the oil and gas industry? a. In kg/m3 b. In lb/ft3 c. In API units d. In LB/Gal

In API units

Introduction of geophysical techniques revolutionized the methods of petroleum exploration during the modern era a. True b. False

True

When the P-to-S-wave velocity ratio (Vp/Vs) increases the Poisson's ratio: a. Increases b. Decreases c. Does not change

Increases

Why do you think the prestack waveform inversion (PWI) provide much superior subsurface model compared to poststack or amplitude variation with offset inversion? a. PWI takes much longer time to run than the other two, so it better be good. b. PWI uses complex effects of wave propagation into its algorithm and the other two methods are based on simplified physics. Consequently, PWI produces superior results than the other two. c. PWI needs a parallel computer to run but the other two methods do not.

PWI uses complex effects of wave propagation into its algorithm and the other two methods are based on simplified physics. Consequently, PWI produces superior results than the other two

Neutron logs are sensitive to: a. Formation radioactivity b. Water saturation c. Porosity d. Seismic velocity e. Density

Porosity

To extract P- and S-Wave velocity and density from seismic data, what type of inversion would you use? a. Prestack inversion (either amplitude variation with offset or prestack waveform inversion) b. Poststack inversion (i.e., the inversion of the stacked seismic data)

Prestack inversion (either amplitude variation with offset or prestack waveform inversion)

In the fluid substitution equations, what is the physical explanation of the fact that the rigidity modulus of the fluid-saturated rock (µsat) is equal to that of the dry rock (µdry)? a. Rigidity modulus of the rock matrix and that of fluids is about same such that the shear waves propagate at the same speed through the rock matrix and through the pore fluids. b. Rigidity modulus of the fluids is zero and the shear waves do not propagate through the pores and they propagate only through the rock matrix.

Rigidity modulus of the fluids is zero and the shear waves do not propagate through the pores and they propagate only through the rock matrix.

The most effective geophysical method in petroleum exploration is a. Gravity b. Electromagnetic c. Seismic d. Magnetic e. Electrical Resistivity

Seismic

Combing seismic with electromagnetic (EM) methods are gradually becoming a popular exploration tool. Typically, seismic method provides subsurface velocities (P and S) and to some extent density. EM, on the other hand provides the subsurface resistivity. Keeping this in mind, what in your opinion is the advantage for combining these two methods? a. Seismic velocities are not sensitive to porosity, but the EM resistivity is. Therefore combining them can provide a good control of subsurface porosity. b. There is a direct relationship between seismic velocities and EM resistivity. Therefore, running them together provides a better description of the subsurface reservoir properties compared to using each method individually. c. Seismic velocities are sensitive to porosity but less sensitive to the presence of fluids occupying the pores. EM resistivity, on the other hand is very sensitive to the fluids in the pores. Therefore using seismic and EM together can potentially give not only the porosity, but the fluid content.

Seismic velocities are sensitive to porosity but less sensitive to the presence of fluids occupying the pores. EM resistivity, on the other hand is very sensitive to the fluids in the pores. Therefore using seismic and EM together can potentially give not only the porosity, but the fluid content

In fluid substitutions when you substitute a 100% brine saturate rock to 100% gas, the shear wave velocity (Vs) will a. Drastically decrease b. Stay about the same or slightly increase c. Drastically increase d. Slightly decrease

Stay about the same or slightly increase

Gravity methods of geophysical exploration could be effective in delineating a. Structural traps only b. Stratigraphic traps only c. Structural, stratigraphic, and possibly other types of traps

Structural, stratigraphic, and possibly other types of traps

What is the difference between the bulk modulus of the dry rock (Kdry) and that of the frame (Ko) used in the fluid substitution equation? a. They are exactly the same b. They are not able the same, but approximately equal for all practical purposes c. The frame bulk modulus (Ko) is the average bulk modulus of the minerals that constitute the solid part of the rock while they dry rock bulk modulus (Kdry) is the bulk modulus of the rock where all its pores and empty.

The frame bulk modulus (Ko) is the average bulk modulus of the minerals that constitute the solid part of the rock while they dry rock bulk modulus (Kdry) is the bulk modulus of the rock where all its pores and empty.

Distribution of the gas hydrate in the world oceans suggest that it could be a potential source of energy in the future a. True b. False

True

During the first millennium AD primary use of oil was medication, waterproofing, and warfare a. True b. False

True

Can porosity be calculated from the density and sonic logs? a. Yes b. No

Yes

Does areas of high salinity from the regional isohaline maps indicate possibility of rich oil/gas accumulations: a. Yes b. No

Yes

Does the geothermal gradient depend upon the subsurface lithology? a. Yes b. No

Yes