2451502
Pregunta 1
Pregunta
Is the amount of pore space the most important factor controlling electrical conductivity?
Respuesta
- True
- False
Pregunta 2
Pregunta
What are the types of current flow?
Respuesta
-
Electronic, Ionic
-
Metallic, Aqueous
Pregunta 3
Pregunta
What are the two mechanisms by which we recognise the presence of an electrical inhomogeneity in the
Earth?
Respuesta
-
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 di ferent electrical properties.
-
By generating currents that not penetrate the boundary between two regions with different electrical properties
Pregunta 4
Pregunta
The penetration of an electromagnetic field into the earth depends on:
Respuesta
-
Frequency of oscillation
-
Conductivity of the earth
-
Depth of investigation
-
Current flow paths
Pregunta 5
Pregunta
What is an inductive response
Respuesta
-
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.
Pregunta 6
Pregunta
Specific exploration problems are characterised by speci c ranges in depth of interest leading to dif erent preferred frequencies. What are the range of depths and frequencies used in Oil and Gas exploration?
Respuesta
-
Frequency range: 1-10^-4 Hz Depths 10-1000 m
-
Frequency range: 100-10^-1 Hz Depths 10-100 m
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Frequency range: 10-10^-3 Hz Depths 1-100 m
Pregunta 7
Pregunta
How is called a measure of how easy it is to produce an electrical polarisation within a material?
Respuesta
-
Galvanic Response
-
Inductive Response
-
Dielectric Constant
-
Permitivity of the material
Pregunta 8
Pregunta
The electrical properties of the rocks depend on...
Respuesta
-
The constituent minerals
-
Their mineral associations
-
Rock porosity
-
Fluid content
-
Permitivity
-
Dielectric constant
Pregunta 9
Pregunta
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)
Respuesta
- True
- False
Pregunta 10
Pregunta
The materials can be classified according to their conductivity into groups. Select the groups:
Respuesta
-
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
Pregunta 11
Pregunta
Mostly, the conduction nature in rocks is mainly electronic (Metallic conduction and/or Electronic semi-conductors)
Respuesta
- True
- False
Pregunta 12
Pregunta
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
Respuesta
- True
- False
Pregunta 13
Pregunta
In terms of Metallic conduction, it can be said that the conductivity in metals depends on:
Respuesta
-
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
Pregunta 14
Pregunta
Fluid conductivity depends also upon temperature because the mobility of the ions in solution decreases with temperature.
Respuesta
- True
- False
Pregunta 15
Pregunta
Metallic conductors resistivity depends on temperature. When the temperature increases the conductivity of the metal decreases.
Respuesta
- True
- False
Pregunta 16
Pregunta
When an external electric fi eld is applied the electrons accelerate along the fi eld 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
Respuesta
-
The relaxation time
-
Intrinsic time
-
Extrinsic time
Pregunta 17
Pregunta
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.
Respuesta
- True
- False
Pregunta 18
Pregunta
Electronic semi-conductors need a signi cant 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:
Respuesta
-
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.
Pregunta 19
Pregunta
It is possible to obtain movement of ions within a solid due to imperfections
Respuesta
- True
- False
Pregunta 20
Pregunta
In terms of Aqueous Electrolytes, the conductivity will depend on:
Respuesta
-
Amount of water present
-
Salinity
-
Temperature
-
Connectivity
-
Archie's law
-
Cementation factor
Pregunta 21
Pregunta
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:
Respuesta
-
An empirically defined constant
-
the cementation factor
-
Resistivity of the Aqueous solution
-
Porosity
-
Rock's bulk resistivity
-
Formation factor
Pregunta 22
Pregunta
What happens to Archie's law when part of the pore space is filled by air, natural gas, carbon dioxide or petroleum (insulators) ??
Respuesta
-
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
Pregunta 23
Pregunta
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
Respuesta
- True
- False
Pregunta 24
Pregunta
The diminution ratio is the division between the cross-section area of the crack and the cross-section total area
Respuesta
- True
- False
Pregunta 25
Pregunta
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%
Respuesta
-
Porosity
-
Crack
-
Joint
Pregunta 26
Pregunta
The electric permittivity is defines as...
Respuesta
-
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
Pregunta 27
Pregunta
The relative dielectric constant (Er or K) can be defined as...
Respuesta
-
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
Pregunta 28
Pregunta
What are the most important values in terms of relative dielectric constant
Respuesta
-
Water and Soil
-
Basalt, Coal Dolomite
-
Limestone, Granite Quartz
Pregunta 29
Pregunta
When the current flows more easily in some direction than in others is called Anisotropy
Respuesta
- True
- False
Pregunta 30
Pregunta
The longitudinal resistivity is always greater than the transverse resistivity.
Respuesta
- True
- False
Pregunta 31
Pregunta
The anisotropy coefficient SQRT(RT/RL) >= 1
Respuesta
- True
- False
Pregunta 32
Pregunta
Types of anysotropy
Respuesta
-
Azimuthal anisotropy (Dipping layers, Dominant set of vertical fractures)
-
Depth dependant anisotropy (the nature of the fracture fill changes with depth)
-
Transverse
-
Longitudinal
Pregunta 33
Pregunta
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
Respuesta
- True
- False
Pregunta 34
Pregunta
Select the main uses of the SP method
Respuesta
-
Presence of massive ore bodies
-
Sulphide mineralization
-
Groundwater
-
Geothermal
-
Geological mapping
-
Chargeability
Pregunta 35
Pregunta
What is the cheapest and simplest method to apply? (In terms of near-surface geophysics)
Respuesta
-
SP
-
IP
-
ITS
-
Seismic Refraction
-
Gravity
-
GPR
Pregunta 36
Pregunta
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
Respuesta
-
Sulphide ore bodies, Graphite ore bodies, Magnetite, coal and manganese
-
Quartz veins, pegmatites
Pregunta 37
Pregunta
In mineral exploration the components of the SP are called the Mineral Potential and the "Background potential" What are the uses of the latter?
Respuesta
-
Massive ore bodies
-
Disseminated ore bodies
-
Geothermal research
-
Hydrogeological research
Pregunta 38
Pregunta
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.
Respuesta
-
Electrolytic
-
Electronic
-
Dielectric
Pregunta 39
Pregunta
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 ef ects (human activities may also produce SP signals)
Respuesta
-
Electrokinetic Potential
-
Background Potential
-
Diffusion Potential
-
Mineral Potential
Pregunta 40
Pregunta
How is the called one of the main groups of SP that occur in regions of anomalous concentrations of sul fide ores (also near graphite) and
can be of the order of hundreds of mV or even V.
Respuesta
-
Electrokinetic potential
-
Diffusion potential
-
Mineral potential
-
Background potential
Pregunta 41
Pregunta
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?
Respuesta
-
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."
Pregunta 42
Pregunta
The SP potentials tend to increase in positiveness with the direction of water flows as the electric charge flows in the opposite direction.
Respuesta
- True
- False
Pregunta 43
Pregunta
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))
Respuesta
-
Electrokinetic or Streaming potentials
-
Diffusion
-
Electrolytic
Pregunta 44
Pregunta
In practice, to ensure good ground contact in the field and to obtain reliable measurements, What sort of actions should be taken?
Respuesta
-
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)
Pregunta 45
Pregunta
There are diff erent possible arrangements in which the equipment can be deployed?
Respuesta
-
Static array
-
Fixed Spacing
-
Fixed Electrode
Pregunta 46
Pregunta
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).
Respuesta
- True
- False
Pregunta 47
Pregunta
The major advantage of using a fixed spacing SP survey is that generally needs to operators to moves the system
Respuesta
- True
- False
Pregunta 48
Pregunta
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
Respuesta
- True
- False
Pregunta 49
Pregunta
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
Respuesta
- True
- False
Pregunta 50
Pregunta
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
Respuesta
- True
- False
Pregunta 51
Pregunta
SP can be easily executed on Ice.
Respuesta
- True
- False
Pregunta 52
Pregunta
Problems associated with acquiring SP data and things that must be taken into account:
Respuesta
-
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
Pregunta 53
Pregunta
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 in finite space.
Respuesta
- True
- False
Pregunta 54
Pregunta
Consider a vertical, infinite length, ellipsoidal ore body. Sketch the expected SP anomaly profile over this body
Respuesta
-
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).
Pregunta 55
Pregunta
For a tilted ore body how can you determine the depth to the sink
Respuesta
-
From the half-width of the anomaly profile x1/2=h0.73
-
From the half-width of the anomaly profile x1/2=h0.766
Pregunta 56
Pregunta
For a Vertically ore body (finite length l) how can you determine the depth to the sink
Respuesta
-
From the half-width of the anomaly profile x1/2=h0.73
-
From the half-width of the anomaly profile x1/2=h0.766
Pregunta 57
Pregunta
Is the method of the ratio and the method of the Vmin give the true position of the ore body
Respuesta
- True
- False
Pregunta 58
Pregunta
When the profi le 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.
Respuesta
- True
- False
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