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LSU Reservoir Dynamics exam 1
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Undergraduate 3
02/19/2013

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Term
Darcy's law uses ___________ velocity.
Definition
superficial
Term
For Darcy flow, flow always goes from high to low __________.
Definition
potential
Term
_________ is a better model for porous media flow when the Reynolds number is low.
Definition
Darcy's law
Term
Darcy's law is a better model for porous media flow when the Reynolds number is ______.
Definition
low
Term
What are the field units for mu [viscosity] in Darcy's law?
Definition
centipoise
Term
Besides the Reynolds number dependence, list 2 situations in which Darcy's law might not apply for flow in porous media..
Definition
1) The mean free path has to be smaller than the pores
2) Anisotropy
Term
List 3 of the most important and fundamental assumptions used to derive the linearized diffusivity equation.
Definition
1) conservation of mass
2) compressibility is small and constant
3) viscosity (mu) and permeability (k) are constant
Term
Darcy's law is based on ________ flow rates.
Definition
volume
Term
Sort these in ascending order (lowest first): k (true average), kH (harmonic or series average), kA (arithmetic or parallel average
Definition
k(harmonic) < k(true) < k(arithmetic)
Term
Sort these in descending order (highest first): k (true average), kH (harmonic or series average), kA (arithmetic or parallel average
Definition
k(arithmetic) > k(true) > k(harmonic
Term
What are 3 examples of reservoir flow that are roughly spherical?
Definition
1) flow near tip of perforations
2) the tip of a horizontal well not fully penetrating the reservoir
3) partially penetrated well
Term
Compared to an open-hole (uncased) completion, do you expect a perforated well to have Jd more than, less than, or equal to one? Why?
Definition
less than one, bc the perforations have a much smaller inflow area
Term
What is the geometry and compressibility assumptions for the equation,
q = -[(kA)/(mu c x)] * ln [ (1-c(p(x)-po) / (1-c(p(0)-po) ]
Definition
Geometry assumptions: slightly compressible, linear
Compressibility assumptions: small, constant
Term
A reservoir engineer is most concerned with __________.
Definition
reserves estimation
Term
Darcy's law is based on __________.
Definition
superficial reservoir velocity
Term
Economic evaluation of oil and gas fields is usually done by _________.
Definition
Reservoir engineers
Term
The dimensions of permeability are _________.
Definition
Area
(milidarcy is the unit)
Term
In reservoir engineering, the grain size of sedimentary rock is important because coarser-grained rocks ...
a) tend to be stronger
b) indicate a higher-energy environment of depletion
c) tend to have high permeability
d) are easier to drill
Definition
c) coarser-grained rocks tend to have high permeability
Term
In reservoir engineering, the Reynolds number N is useful because ..
a) when it is small, there is no slippage
b) when it is larger, there is no slippage
c) when it is small, there is an additional inertial pressure drop
d) when it is larger, there is an additional inertial pressure drop
Definition
d) when it is larger, there is an additional inertial pressure drop
Term
The "Klinkenberg effect" would be greatest for
a) low pressure gas in fine-grained sand
b) high pressure gas in a fine-grained sand
c) low pressure gas in a course-grained sand
d) high pressure gas in a course-grained sand
Definition
a) low pressure gas in a fine-grained sand
Term
The vertical to horizontal permeability ratio kv/kh is commonly ..
a) less than 1 because of fracturing
b) less than 1 because of the layered nature of reservoirs
c) greater than 1 because of gravity-density effects
d) greater than 1 because of convergent cylindrical flow
Definition
b) less than 1 because of the layered nature of reservoirs
Term
The "Klinkenberg effect" would be best suited for _______ pressure gas in a _______ -grained sand
Definition
low
fine
Term
For what reason is the vertical to horizontal permeability ratio kv/kh commonly less than 1?
Definition
the layered nature of reservoirs
Term
Why is the Reynolds number, N, useful in reservoir engineering?
Definition
When it is larger, there is an additional inertial pressure drop.
Term
In general for heterogeneous systems, the effective permeability is ..
a) greater than the harmonic average
b) less than the harmonic average
c) greater than the arithmetic average and less than the harmonic average
d) greater than the harmonic average and less than the arithmetic average
Definition
d) greater than the harmonic average and less than the arithmetic average
Term
In general for heterogeneous systems, the effective permeability is _________ than the harmonic average and _________ than the arithmetic average.
Definition
greater
less
Term
The skin factor s, is ..
a) a measure of damage due to drilling fluids
b) a simple model for heterogeneities and non-ideal behavior in the near-well region
c) always negative
d) the inverse of the UV-blocking power, s = 1/SPF
Definition
b) a simple model for heterogeneities and non-ideal behavior in the near-well region
Term
Reservoir engineers' main tasks include
a) estimating rock properties
b) predicting rates
c) analyzing well logs
d) separator and facilities configuration
Definition
b) predicting rates
Term
Uncertainty in permeability may not lead to risk if
a) permeability is low
b) porosity is high
c) the facilities are rate constrained
d) we are in an international setting with a production sharing agreement
Definition
c) the facilities are rate constrained
Term
Within a porous media, the highest velocity is
a) on the pore throat surface
b) the superficial velocity
c) the advance velocity
d) the velocity at the center of a pore throat
Definition
d) the velocity at the center of a pore throat
Term
Tortuosity describes
a) the average crookedness of flow paths at the small scale
b) the ratio of surface area to solid volume
c) the effects of inertia
Definition
a) the average crookedness of flow paths at the small scale
Term
Non-darcy, inertia-influenced flow is most significant
a) the velocity is high
b) when the mean free path of gas molecules is short
c) near the well
d) at high Reynolds numbers
Definition
d) at high Reynolds numbers
Term
Slippage will be most significant
a) at low Reynolds numbers
b) for a low pressure, low permeability reservoir
c) for a high pressure, high permeability reservoir
d) for a low pressure, high permeability reservoir
Definition
b) for a low pressure, low permeability reservoir
(low pressure in small pores causes gas slippage)
Term
The permeability tensor is used to
a) correctly model flow at high Reynolds numbers
b) account for mean free molecular paths that are large compared to pore size
c) compute the flow direction in reservoirs that have different permeabilities in different directions
d) linearize the diffusivity equation
Definition
c) compute the flow direction in reservoirs that have different permeabilities in different directions
--> anisotropy
Term
The arithmetic average is
a) only used to compute horizontal average permeability
b) more sensitive to low values than the harmonic average
c) appropriate for series flow
d) appropriate for parallel flow
Definition
d) appropriate for parallel flow
Term
Slippage will be most significant for a _______ pressure, ________ permeability reservoir
Definition
low
low
Term
Is non-darcy, inertia-influenced flow most significant at high or low Reynold's numbers?
Definition
high
Term
The __________ average is appropriate for parallel flow.
Definition
arithmetic
Term
[change in] Ps is
a) the total pressure drop across a zone of altered flow near a wellbore
b) always positive
c) rarely large
d) the additional pressure drop across a zone of altered flow near a wellbore
Definition
d) the additional pressure drop across a zone of altered flow near a wellbore
Term
List exactly three conditions that must be met for Darcy's Law to apply as given on the equation sheet.
Definition
1) incompressible fluid
2) single phase flow
3) flow through homogeneous media
Term
If nothing else is known, what is the appropriate numerical approximation for ln(re/rw)?
Definition
8
Term
Give a typical value for .. the permeability of a good oil reservoir
Definition
1 darcy
Term
Give a typical value for ..
viscosity of a light, Gulf Coast oil
Definition
1 cp
Term
Give a typical value for ..
porosity of a good oil reservoir
Definition
30%
Term
Give a typical value for ..
the ratio ln(re/rw)
Definition
8
Term
A reservoir engineer is most concerned with ___________ and ____________.
Definition
predicting rates and estimating recovery
Term
In developing oil & gas reservoirs , we are most concerned with
a) reservoir properties we are uncertain of
b) reservoir properties that vary over a wide range
c) reservoir properties that cause significant changes in rate or recovery - that have high sensitivity
d) reservoir properties that have high sensitivities and high variability
Definition
a) reservoir properties we are uncertain of
Term
Darcy's law is based on
a) mass flow rate
b) the flow rate at standard conditions
c) the volumetric flow rate at reservoir conditions
d) the volumetric flow rate at standard conditions
Definition
c) the volumetric flow rate at reservoir conditions
Term
In reservoir engineering, the specific area, av (= pore space surface area / rock grain volume) is important because
a) it varies with rock type and affects permeability
b) it is nearly constant and therefore a usual parameter
c) it is easier to estimate than porosity
d) rocks with a higher av have higher rates and recovery
Definition
a) it varies with rock type and affects permeability
Term
Which varies more, an isotropic formation or an anisotripic formation?
Definition
anisotropic
Term
Darcy's law is based on the ___________ flow rate at reservoir conditions.
Definition
volumetric
Term
We may have inertial (or non-Darcy) effects in porous media flow
a) at Reynolds numbers greater than 3
b) at Reynolds numbers greater than about 2100
c) at any Reynolds number near the well because of convergent flow
d) if the mean free path of gas molecules is short compared to the pore size
Definition
a) at Reynolds numbers greater than 3
Term
Slippage or the "Klinkenberg effect" would be greatest in
a) a high-pressure gas shale reservoir
b) a low-pressure gas shale reservoir
c) conventional moderate permeability gas at low pressure
d) an oil reservoir at any pressure
Definition
b) a low-pressure gas shale reservoir
Term
Due to sedimentary layering, the vertical to horizontal permeability ratio, kv/kh, is commonly _________ than 1.
Definition
less
Term
What assumptions does that Navier-Stokes equation make?
Definition
that density is a function of pressure only
conservation of mass, momentum, and energy
Term
Darcy's law predicts
a) the superficial velocity at reservoir conditions
b) the superficial velocity at standard conditions
c) the mass flow rate at reservoir conditions
d) the volumetric flow rate at standard conditions
Definition
a) the superficial velocity at reservoir conditions
Term
We may have inertial (or non-Darcy) effects in porous media flow
a) near the well for high-rate wells
b) at Reynolds numbers greater than about 2100
c) far from the well for high-rate wells
d) if the mean free path of gas molecules is short compared to the pore size
Definition
a) near the well for high-rate wells
Term
Flow to a well at any pressure is best calculated using
a) pressure
b) potential
c) pressure-squared
d) the spherical flow formula
Definition
b) potential
Term
For sedimentary rocks, the tortuosity is
a) unimportant
b) less than 1
c) usually greater in the vertical compared to horizontal direction
d) isotropic
Definition
c) usually greater in the vertical compared to horizontal direction
Term
The highest velocity in a porous medium is
a) the superficial velocity
b) the velocity near pore centers
c) the velocity near pore walls
d) the average interstitial velocity
Definition
b) the velocity near pore centers
Term
The least convergent flow regime is
a) steady state
b) linear flow
c) compressible flow
d) spherical flow
Definition
b) linear flow
Term
The vertical permeability in an unfractured layered system should be calculated using
a) the geometric average
b) the harmonic average
c) the arithmetic average
d) Green's functions
Definition
c) the arithmetic average
Term
We expect a perforated well may have a positive skin because of
a) slippage
b) lower surface area open to flow
c) linear flow
d) late-time pseudoradial flow
Definition
b) lower surface area open to flow
Term
Compared to an unaltered well, at the same flow rate, the pressure gradient will be
a) the same in the outer region, regardless of s
b) higher for the damaged well in the near well region (s > 0)
c) lower for the stimulated well in the near well region (s < 0)
d) all of the above
Definition
d) all of the above
Term
Compared to an unaltered well, at the same total pressure drop, the pressure gradient will be
a) the same in the outer region, regardless of s
b) higher for the damaged well in the near well region (s > 0)
c) lower for the stimulated well in the near well region (s < 0)
d) all of the above
Definition
b) higher for the damaged well in the near well region (s > 0)
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