Geoelectrics

Pregunta 1 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 2 de 58

1

What are the types of current flow?

Selecciona una de las siguientes respuestas posibles:

Electronic, Ionic
Metallic, Aqueous

Explicación

Pregunta 3 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 4 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 5 de 58

1

What is an inductive response

Selecciona una de las siguientes respuestas posibles:

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.

Explicación

Pregunta 6 de 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?

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 7 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

Galvanic Response
Inductive Response
Dielectric Constant
Permitivity of the material

Explicación

Pregunta 8 de 58

1

The electrical properties of the rocks depend on...

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 9 de 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)

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 10 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 11 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 12 de 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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 13 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 14 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 15 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 16 de 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

Selecciona una de las siguientes respuestas posibles:

The relaxation time
Intrinsic time
Extrinsic time

Explicación

Pregunta 17 de 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.

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 18 de 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:

Selecciona una de las siguientes respuestas posibles:

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.

Explicación

Pregunta 19 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 20 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 21 de 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:

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 22 de 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) ??

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 23 de 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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 24 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 25 de 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%

Selecciona una de las siguientes respuestas posibles:

Porosity
Crack
Joint

Explicación

Pregunta 26 de 58

1

The electric permittivity is defines as...

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 27 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 28 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

Water and Soil
Basalt, Coal Dolomite
Limestone, Granite Quartz

Explicación

Pregunta 29 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 30 de 58

1

The longitudinal resistivity is always greater than the transverse resistivity.

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 31 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 32 de 58

1

Types of anysotropy

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 33 de 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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 34 de 58

1

Select the main uses of the SP method

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 35 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

SP
IP
ITS
Seismic Refraction
Gravity
GPR

Explicación

Pregunta 36 de 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

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 37 de 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?

Selecciona una o más de las siguientes respuestas posibles:

Massive ore bodies
Disseminated ore bodies
Geothermal research
Hydrogeological research

Explicación

Pregunta 38 de 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.

Selecciona una de las siguientes respuestas posibles:

Electrolytic
Electronic
Dielectric

Explicación

Pregunta 39 de 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)

Selecciona una de las siguientes respuestas posibles:

Electrokinetic Potential
Background Potential
Diffusion Potential
Mineral Potential

Explicación

Pregunta 40 de 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.

Selecciona una de las siguientes respuestas posibles:

Electrokinetic potential
Diffusion potential
Mineral potential
Background potential

Explicación

Pregunta 41 de 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?

Selecciona una o más de las siguientes respuestas posibles:

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."

Explicación

Pregunta 42 de 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.

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 43 de 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))

Selecciona una de las siguientes respuestas posibles:

Electrokinetic or Streaming potentials
Diffusion
Electrolytic

Explicación

Pregunta 44 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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)

Explicación

Pregunta 45 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

Static array
Fixed Spacing
Fixed Electrode

Explicación

Pregunta 46 de 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).

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 47 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 48 de 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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 49 de 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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 50 de 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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 51 de 58

1

SP can be easily executed on Ice.

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 52 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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

Explicación

Pregunta 53 de 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.

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 54 de 58

1

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

Selecciona una o más de las siguientes respuestas posibles:

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).

Explicación

Pregunta 55 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 56 de 58

1

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

Selecciona una de las siguientes respuestas posibles:

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

Explicación

Pregunta 57 de 58

1

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

Selecciona uno de los siguientes:

VERDADERO
FALSO

Explicación

Pregunta 58 de 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.

Selecciona uno de los siguientes:

VERDADERO
FALSO

	Creado por Vanerahal hace más de 9 años

Exam1

Geoelectrics

Pregunta 1 de 58

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

Selecciona uno de los siguientes:

Explicación

Pregunta 2 de 58

What are the types of current flow?

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 3 de 58

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

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 4 de 58

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

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 5 de 58

What is an inductive response

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 6 de 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?

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 7 de 58

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

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 8 de 58

The electrical properties of the rocks depend on...

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 9 de 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)

Selecciona uno de los siguientes:

Explicación

Pregunta 10 de 58

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

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 11 de 58

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

Selecciona uno de los siguientes:

Explicación

Pregunta 12 de 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

Selecciona uno de los siguientes:

Explicación

Pregunta 13 de 58

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

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 14 de 58

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

Selecciona uno de los siguientes:

Explicación

Pregunta 15 de 58

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

Selecciona uno de los siguientes:

Explicación

Pregunta 16 de 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

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 17 de 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.

Selecciona uno de los siguientes:

Explicación

Pregunta 18 de 58

Selecciona una de las siguientes respuestas posibles:

Explicación

Pregunta 19 de 58

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

Selecciona uno de los siguientes:

Explicación

Pregunta 20 de 58

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

Selecciona una o más de las siguientes respuestas posibles:

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