Geoelectrics

Frage 1 von 58

1

Is the amount of pore space the most important factor controlling electrical conductivity?

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 2 von 58

1

What are the types of current flow?

Wähle eine der folgenden:

Electronic, Ionic
Metallic, Aqueous

Erklärung

Frage 3 von 58

1

What are the two mechanisms by which we recognise the presence of an electrical inhomogeneity in the
Earth?

Wähle eine oder mehr der folgenden:

By the generation of current circulating within a conductive body
By the generation of current not circulating within a resistive body
By generating currents that penetrate the boundary between two regions with diferent electrical properties.
By generating currents that not penetrate the boundary between two regions with different electrical properties

Erklärung

Frage 4 von 58

1

The penetration of an electromagnetic field into the earth depends on:

Wähle eine oder mehr der folgenden:

Frequency of oscillation
Conductivity of the earth
Depth of investigation
Current flow paths

Erklärung

Frage 5 von 58

1

What is an inductive response

Wähle eine der folgenden:

An inductive response occurs when current flows within the conductive region in proportion to its conductivity and the time rate of change of the applied magnetic field
An inductive response occurs when the currents will be distorted by the presence of the anomalously conductive body.

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Frage 6 von 58

1

Specific exploration problems are characterised by specic ranges in depth of interest leading to diferent preferred frequencies. What are the range of depths and frequencies used in Oil and Gas exploration?

Wähle eine der folgenden:

Frequency range: 1-10^-4 Hz
Depths 10-1000 m
Frequency range: 100-10^-1 Hz
Depths 10-100 m
Frequency range: 10-10^-3 Hz
Depths 1-100 m

Erklärung

Frage 7 von 58

1

How is called a measure of how easy it is to produce an electrical polarisation within a material?

Wähle eine der folgenden:

Galvanic Response
Inductive Response
Dielectric Constant
Permitivity of the material

Erklärung

Frage 8 von 58

1

The electrical properties of the rocks depend on...

Wähle eine oder mehr der folgenden:

The constituent minerals
Their mineral associations
Rock porosity
Fluid content
Permitivity
Dielectric constant

Erklärung

Frage 9 von 58

1

The main difference between resistivity-resistance and conductivity-conductance is that the former is related to the material and is a physical property of it (intensive property: does not depend on the system size or the amount of material in the system)

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 10 von 58

1

The materials can be classified according to their conductivity into groups. Select the groups:

Wähle eine oder mehr der folgenden:

Conductors, conductivity less than 10^5 S/m
Semi-conductors 10^-8 S/m < Conductivity < 10^5 S/m
Insulators Conductivity < 10^-8 S/m
Metallic conductivity less than 10^5 S/m
Sulphides 10^-8 S/m < Conductivity < 10^5 S/m
Aislators Conductivity < 10^-8 S/m

Erklärung

Frage 11 von 58

1

Mostly, the conduction nature in rocks is mainly electronic (Metallic conduction and/or Electronic semi-conductors)

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 12 von 58

1

The main difference between Metallic Conduction and Electronic Semiconductors is that the latter needs a much more significant amount of energy (heat) for the electrons to become dissociated from their home atoms

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 13 von 58

1

In terms of Metallic conduction, it can be said that the conductivity in metals depends on:

Wähle eine der folgenden:

the number density of free electrons, the electron charge and the electron mass.
the number density of free electrons, the electron charge, the electron mass and the relaxation time

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Frage 14 von 58

1

Fluid conductivity depends also upon temperature because the mobility of the ions in solution decreases with temperature.

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 15 von 58

1

Metallic conductors resistivity depends on temperature. When the temperature increases the conductivity of the metal decreases.

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 16 von 58

1

When an external electric field is applied the electrons accelerate along the field lines and a current is produced. This
current would increase without limit if the electrons did not occasionally "collide" with the nuclei. The average
time between collisions for a given electron is called

Wähle eine der folgenden:

The relaxation time
Intrinsic time
Extrinsic time

Erklärung

Frage 17 von 58

1

The electronic semi-conductors are metallic materials just as native metals, the only difference is that they have a smaller number of free electrons with lower mobility.

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 18 von 58

1

Electronic semi-conductors need a signicant amount of
energy for the electron to become dissociated from their "home" atoms. One source of this is heat, the number of conduction electrons in these type of material depends on:
Energy required to free an electron, Boltzmann Constant, and the absolute temperature
So it can be concluded that:

Wähle eine der folgenden:

For semiconductors a higher temperature results in more free electrons and therefore a higher conductivity.
For semiconductors a higher temperature results in more free electrons and therefore a lower conductivity.
For semiconductors a higher temperature results in less free electrons and therefore a higher conductivity.
For semiconductors a higher temperature results in less free electrons and therefore a lower conductivity.

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Frage 19 von 58

1

It is possible to obtain movement of ions within a solid due to imperfections

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 20 von 58

1

In terms of Aqueous Electrolytes, the conductivity will depend on:

Wähle eine oder mehr der folgenden:

Amount of water present
Salinity
Temperature
Connectivity
Archie's law
Cementation factor

Erklärung

Frage 21 von 58

1

Archie’s Law: It is a purely empirical law attempting to describe ion flow (mostly sodium and chloride) in clean, consolidated sands, with varying intergranular porosity. Electrical conduction is assumed not to be present within the rock grains or in fluids other than water.
So it can be said that the variables within the equation are:

Wähle eine oder mehr der folgenden:

An empirically defined constant
the cementation factor
Resistivity of the Aqueous solution
Porosity
Rock's bulk resistivity
Formation factor

Erklärung

Frage 22 von 58

1

What happens to Archie's law when part of the pore space is filled by air, natural gas, carbon dioxide or petroleum (insulators) ??

Wähle eine der folgenden:

The equation remains the same
an empirical constant is added
Boltzmann constant is added to the equation
the volume fraction of pores with water power to the saturation exponent is added

Erklärung

Frage 23 von 58

1

The tortuosity is defined by the relation between the average length of the path through the crack and the length of the rock lc/l

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 24 von 58

1

The diminution ratio is the division between the cross-section area of the crack and the cross-section total area

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Frage 25 von 58

1

Is a measure of the void (i.e., "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0 and 100%

Wähle eine der folgenden:

Porosity
Crack
Joint

Erklärung

Frage 26 von 58

1

The electric permittivity is defines as...

Wähle eine der folgenden:

a measure of the degree to which a given material becomes polarized.
electric dipole moment per unit volume
the amount of charge which is separated and the distance through which it has moved

Erklärung

Frage 27 von 58

1

The relative dielectric constant (Er or K) can be defined as...

Wähle eine der folgenden:

the ratio of the material's permittivity to the permittivity of free space
the subtraction of the material's permittivity to the permittivity of free space
the multiplication of the material's permittivity to the permittivity of free space

Erklärung

Frage 28 von 58

1

What are the most important values in terms of relative dielectric constant

Wähle eine der folgenden:

Water and Soil
Basalt, Coal Dolomite
Limestone, Granite Quartz

Erklärung

Frage 29 von 58

1

When the current flows more easily in some direction than in others is called Anisotropy

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 30 von 58

1

The longitudinal resistivity is always greater than the transverse resistivity.

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 31 von 58

1

The anisotropy coefficient SQRT(RT/RL) >= 1

Wähle eins der folgenden:

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FALSCH

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Frage 32 von 58

1

Types of anysotropy

Wähle eine oder mehr der folgenden:

Azimuthal anisotropy (Dipping layers, Dominant set of vertical fractures)
Depth dependant anisotropy (the nature of the fracture fill changes with depth)
Transverse
Longitudinal

Erklärung

Frage 33 von 58

1

The main difference between IP and SP is that the former is mainly used to determine massive ore bodies whereas the latter is mainly used to determine disseminated ore bodies

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 34 von 58

1

Select the main uses of the SP method

Wähle eine oder mehr der folgenden:

Presence of massive ore bodies
Sulphide mineralization
Groundwater
Geothermal
Geological mapping
Chargeability

Erklärung

Frage 35 von 58

1

What is the cheapest and simplest method to apply? (In terms of near-surface geophysics)

Wähle eine der folgenden:

SP
IP
ITS
Seismic Refraction
Gravity
GPR

Erklärung

Frage 36 von 58

1

The sign of the potential is an important diagnostic factor in the interpretation of SP anomalies. What kind of mineral potentials are expected for negative anomalies of hundreds of mV

Wähle eine der folgenden:

Sulphide ore bodies, Graphite ore bodies, Magnetite, coal and manganese
Quartz veins, pegmatites

Erklärung

Frage 37 von 58

1

In mineral exploration the components of the SP are called the Mineral Potential and the "Background potential" What are the uses of the latter?

Wähle eine oder mehr der folgenden:

Massive ore bodies
Disseminated ore bodies
Geothermal research
Hydrogeological research

Erklärung

Frage 38 von 58

1

What type of electric conduction occurs in very weakly conducting materials (or insulators) when an external alternating
current is applied, so causing atomic electrons to be shifted slightly with respect to their nuclie.

Wähle eine der folgenden:

Electrolytic
Electronic
Dielectric

Erklärung

Frage 39 von 58

1

How is called one of the main groups of SP that are generally of the order of mV and mainly arise due to water circulation, small
mineral quantities, biologic and topographic efects (human activities may also produce SP signals)

Wähle eine der folgenden:

Electrokinetic Potential
Background Potential
Diffusion Potential
Mineral Potential

Erklärung

Frage 40 von 58

1

How is the called one of the main groups of SP that occur in regions of anomalous concentrations of sulfide ores (also near graphite) and
can be of the order of hundreds of mV or even V.

Wähle eine der folgenden:

Electrokinetic potential
Diffusion potential
Mineral potential
Background potential

Erklärung

Frage 41 von 58

1

Buried sulphide masses are known to cause SP anomalies. In terms of the effect observed and the physical cause of this effect. Which of the following is true?

Wähle eine oder mehr der folgenden:

Groundwater is thought to be common factor responsible for SP. The potentials are generated by the flow of water by water acting as an electrolyte and as a solvent of different minerals.
A negative anomaly of hundreds of mV is expected
A postive anomaly of hundreds of mV is expected
One proposal can explain all SP observations
1. Above water table: dissolved electrolytes gain electrons from the ore body and are reduced.
2. Below the water table: an oxidation reaction occurs transferring electrons back to the ore body.
3. Electrons are then conducted through the ore body completing the circuit.
It is possible that only the presence of variable redox conditions within the subsurface is required to generate large SP anomalies, without need of a subsurface conductor to "close the circuit."

Erklärung

Frage 42 von 58

1

The SP potentials tend to increase in positiveness with the direction of water flows as the electric charge flows in the opposite direction.

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 43 von 58

1

How is called the mechanism by which SP anomalies are generated that is useful to map subsurface barriers or conduits of flow. (These are generated by the flow of aqueous electrolytes through narrow channels (pores))

Wähle eine der folgenden:

Electrokinetic or Streaming potentials
Diffusion
Electrolytic

Erklärung

Frage 44 von 58

1

In practice, to ensure good ground contact in the field and to obtain reliable measurements, What sort of actions should be taken?

Wähle eine oder mehr der folgenden:

Porous-pot electrodes
Non-porous electrodes
The Resistance of the voltimeter must be large enough 10^8 Ohm
The electrodes should be kept dry and shaded to ensure good ground contact (when the fixed electrode is used)
The electrodes should be kept wet and shaded to ensure good ground contact (when the fixed electrode is used)

Erklärung

Frage 45 von 58

1

There are different possible arrangements in which the equipment can be deployed?

Wähle eine oder mehr der folgenden:

Static array
Fixed Spacing
Fixed Electrode

Erklärung

Frage 46 von 58

1

The advantage of using a fixed spacing SP survey is that you can use a shorter wire and the reduced importance of telluric currents (generally long-wavelength currents induced in the ground by geomagnetic fluctuations).

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 47 von 58

1

The major advantage of using a fixed spacing SP survey is that generally needs to operators to moves the system

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 48 von 58

1

The gridded measurements in the SP fixed spacing survey should ultimately form a closed loop and the sum of all potentials within that loop should equal zero if not the remainder represents an error and should not be distributed among the readings

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 49 von 58

1

The main disadvantage of using a fixed electrode system (sp) is that system include generally more measurement errors and that is not easy to perform by a single operator

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 50 von 58

1

The main advantage of using a fixed electrode system is that the larger separation between electrodes does not allow telluric currents to influence the results

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 51 von 58

1

SP can be easily executed on Ice.

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 52 von 58

1

Problems associated with acquiring SP data and things that must be taken into account:

Wähle eine oder mehr der folgenden:

Electrode polarization
Rain (Ground-contact strength and ground conductivity)
Telluric variations (Daily drift variations)
Artificial sources of electricity in the surroundings (or in the vicinity)
A shift in the equipotential lines in relation to an ore body (current will flow preferentially in the less resistive unit.)
Longness of the wire

Erklärung

Frage 53 von 58

1

the observed current and potential due to a single source in a half space is identical to that from the method of images inspired model of two sources in an infinite space.

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 54 von 58

1

Consider a vertical, infinite length, ellipsoidal ore body. Sketch the expected SP anomaly profile over this body

Wähle eine oder mehr der folgenden:

A vertically body will have no positive anomaly
A vertically body will have a positive anomaly
the anomaly peaks are not simply located above the poles
the anomaly peaks are simply located above the poles
For a dipping body, the negative anomaly associated with the shallower, negative pole is much more pronounced
For a dipping body, the negative anomaly associated with the shallower, negative pole is much less pronounced
A vertically body will have a negative anomaly that will be centered on the negative pole (in an homogeneous medium).
A vertically body will have a positive anomaly that will be centered on the negative pole (in an homogeneous medium).

Erklärung

Frage 55 von 58

1

For a tilted ore body how can you determine the depth to the sink

Wähle eine der folgenden:

From the half-width of the anomaly profile x1/2=h0.73
From the half-width of the anomaly profile x1/2=h0.766

Erklärung

Frage 56 von 58

1

For a Vertically ore body (finite length l) how can you determine the depth to the sink

Wähle eine der folgenden:

From the half-width of the anomaly profile x1/2=h0.73
From the half-width of the anomaly profile x1/2=h0.766

Erklärung

Frage 57 von 58

1

Is the method of the ratio and the method of the Vmin give the true position of the ore body

Wähle eins der folgenden:

WAHR
FALSCH

Erklärung

Frage 58 von 58

1

When the profile is drawn the
reference (zero) potential needs to be set as the value for which the potential becomes constant far from the
body, this process is helped by a good lateral extent of measurements and a low level of noise.

Wähle eins der folgenden:

WAHR
FALSCH

	Erstellt von Vanerahal vor mehr als 9 Jahre

Exam1

Geoelectrics

Geoelectrics

Frage 1 von 58

Is the amount of pore space the most important factor controlling electrical conductivity?

Wähle eins der folgenden:

Erklärung

Frage 2 von 58

What are the types of current flow?

Wähle eine der folgenden:

Erklärung

Frage 3 von 58

What are the two mechanisms by which we recognise the presence of an electrical inhomogeneity in the Earth?

Wähle eine oder mehr der folgenden:

Erklärung

Frage 4 von 58

The penetration of an electromagnetic field into the earth depends on:

Wähle eine oder mehr der folgenden:

Erklärung

Frage 5 von 58

What is an inductive response

Wähle eine der folgenden:

Erklärung

Frage 6 von 58

Specific exploration problems are characterised by specic ranges in depth of interest leading to diferent preferred frequencies. What are the range of depths and frequencies used in Oil and Gas exploration?

Wähle eine der folgenden:

Erklärung

Frage 7 von 58

How is called a measure of how easy it is to produce an electrical polarisation within a material?

Wähle eine der folgenden:

Erklärung

Frage 8 von 58

The electrical properties of the rocks depend on...

Wähle eine oder mehr der folgenden:

Erklärung

Frage 9 von 58

The main difference between resistivity-resistance and conductivity-conductance is that the former is related to the material and is a physical property of it (intensive property: does not depend on the system size or the amount of material in the system)

Wähle eins der folgenden:

Erklärung

Frage 10 von 58

The materials can be classified according to their conductivity into groups. Select the groups:

Wähle eine oder mehr der folgenden:

Erklärung

Frage 11 von 58

Mostly, the conduction nature in rocks is mainly electronic (Metallic conduction and/or Electronic semi-conductors)

Wähle eins der folgenden:

Erklärung

Frage 12 von 58

The main difference between Metallic Conduction and Electronic Semiconductors is that the latter needs a much more significant amount of energy (heat) for the electrons to become dissociated from their home atoms

Wähle eins der folgenden:

Erklärung

Frage 13 von 58

In terms of Metallic conduction, it can be said that the conductivity in metals depends on:

Wähle eine der folgenden:

Erklärung

Frage 14 von 58

Fluid conductivity depends also upon temperature because the mobility of the ions in solution decreases with temperature.

Wähle eins der folgenden:

Erklärung

Frage 15 von 58

Metallic conductors resistivity depends on temperature. When the temperature increases the conductivity of the metal decreases.

Wähle eins der folgenden:

Erklärung

Frage 16 von 58

When an external electric field is applied the electrons accelerate along the field lines and a current is produced. This current would increase without limit if the electrons did not occasionally "collide" with the nuclei. The average time between collisions for a given electron is called

Wähle eine der folgenden:

Erklärung

Frage 17 von 58

The electronic semi-conductors are metallic materials just as native metals, the only difference is that they have a smaller number of free electrons with lower mobility.

Wähle eins der folgenden:

Erklärung

Frage 18 von 58

Wähle eine der folgenden:

Erklärung

Frage 19 von 58

It is possible to obtain movement of ions within a solid due to imperfections

Wähle eins der folgenden:

Erklärung

Frage 20 von 58

In terms of Aqueous Electrolytes, the conductivity will depend on:

What are the two mechanisms by which we recognise the presence of an electrical inhomogeneity in the
Earth?

When an external electric field is applied the electrons accelerate along the field lines and a current is produced. This
current would increase without limit if the electrons did not occasionally "collide" with the nuclei. The average
time between collisions for a given electron is called