Term
| Darcy's law uses ___________ velocity. |
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Definition
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Term
| For Darcy flow, flow always goes from high to low __________. |
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Definition
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Term
| _________ is a better model for porous media flow when the Reynolds number is low. |
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Definition
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Term
| Darcy's law is a better model for porous media flow when the Reynolds number is ______. |
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Definition
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Term
| What are the field units for mu [viscosity] in Darcy's law? |
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Definition
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Term
| Besides the Reynolds number dependence, list 2 situations in which Darcy's law might not apply for flow in porous media.. |
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Definition
1) The mean free path has to be smaller than the pores
2) Anisotropy |
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Term
| List 3 of the most important and fundamental assumptions used to derive the linearized diffusivity equation. |
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Definition
1) conservation of mass
2) compressibility is small and constant
3) viscosity (mu) and permeability (k) are constant |
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Term
| Darcy's law is based on ________ flow rates. |
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Definition
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Term
| Sort these in ascending order (lowest first): k (true average), kH (harmonic or series average), kA (arithmetic or parallel average |
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Definition
| k(harmonic) < k(true) < k(arithmetic) |
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Term
| Sort these in descending order (highest first): k (true average), kH (harmonic or series average), kA (arithmetic or parallel average |
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Definition
| k(arithmetic) > k(true) > k(harmonic |
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Term
| What are 3 examples of reservoir flow that are roughly spherical? |
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Definition
1) flow near tip of perforations
2) the tip of a horizontal well not fully penetrating the reservoir
3) partially penetrated well |
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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? |
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Definition
| less than one, bc the perforations have a much smaller inflow area |
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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) ] |
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Definition
Geometry assumptions: slightly compressible, linear
Compressibility assumptions: small, constant |
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Term
| A reservoir engineer is most concerned with __________. |
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Definition
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Term
| Darcy's law is based on __________. |
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Definition
| superficial reservoir velocity |
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Term
| Economic evaluation of oil and gas fields is usually done by _________. |
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Definition
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Term
| The dimensions of permeability are _________. |
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Definition
Area
(milidarcy is the unit) |
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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 |
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Definition
| c) coarser-grained rocks tend to have high permeability |
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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 |
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Definition
| d) when it is larger, there is an additional inertial pressure drop |
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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 |
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Definition
| a) low pressure gas in a fine-grained sand |
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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 |
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Definition
| b) less than 1 because of the layered nature of reservoirs |
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Term
| The "Klinkenberg effect" would be best suited for _______ pressure gas in a _______ -grained sand |
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Definition
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Term
| For what reason is the vertical to horizontal permeability ratio kv/kh commonly less than 1? |
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Definition
| the layered nature of reservoirs |
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Term
| Why is the Reynolds number, N, useful in reservoir engineering? |
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Definition
| When it is larger, there is an additional inertial pressure drop. |
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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 |
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Definition
| d) greater than the harmonic average and less than the arithmetic average |
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Term
| In general for heterogeneous systems, the effective permeability is _________ than the harmonic average and _________ than the arithmetic average. |
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Definition
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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 |
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Definition
| b) a simple model for heterogeneities and non-ideal behavior in the near-well region |
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Term
Reservoir engineers' main tasks include
a) estimating rock properties
b) predicting rates
c) analyzing well logs
d) separator and facilities configuration |
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Definition
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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 |
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Definition
| c) the facilities are rate constrained |
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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 |
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Definition
| d) the velocity at the center of a pore throat |
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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 |
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Definition
| a) the average crookedness of flow paths at the small scale |
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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 |
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Definition
| d) at high Reynolds numbers |
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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 |
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Definition
b) for a low pressure, low permeability reservoir
(low pressure in small pores causes gas slippage) |
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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 |
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Definition
c) compute the flow direction in reservoirs that have different permeabilities in different directions
--> anisotropy |
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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 |
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Definition
| d) appropriate for parallel flow |
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Term
| Slippage will be most significant for a _______ pressure, ________ permeability reservoir |
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Definition
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Term
| Is non-darcy, inertia-influenced flow most significant at high or low Reynold's numbers? |
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Definition
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Term
| The __________ average is appropriate for parallel flow. |
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Definition
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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 |
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Definition
| d) the additional pressure drop across a zone of altered flow near a wellbore |
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Term
| List exactly three conditions that must be met for Darcy's Law to apply as given on the equation sheet. |
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Definition
1) incompressible fluid
2) single phase flow
3) flow through homogeneous media |
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Term
| If nothing else is known, what is the appropriate numerical approximation for ln(re/rw)? |
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Definition
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Term
| Give a typical value for .. the permeability of a good oil reservoir |
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Definition
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Term
Give a typical value for ..
viscosity of a light, Gulf Coast oil |
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Definition
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Term
Give a typical value for ..
porosity of a good oil reservoir |
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Definition
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Term
Give a typical value for ..
the ratio ln(re/rw) |
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Definition
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Term
| A reservoir engineer is most concerned with ___________ and ____________. |
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Definition
| predicting rates and estimating recovery |
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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 |
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Definition
| a) reservoir properties we are uncertain of |
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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 |
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Definition
| c) the volumetric flow rate at reservoir conditions |
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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 |
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Definition
| a) it varies with rock type and affects permeability |
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Term
| Which varies more, an isotropic formation or an anisotripic formation? |
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Definition
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Term
| Darcy's law is based on the ___________ flow rate at reservoir conditions. |
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Definition
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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 |
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Definition
| a) at Reynolds numbers greater than 3 |
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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 |
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Definition
| b) a low-pressure gas shale reservoir |
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Term
| Due to sedimentary layering, the vertical to horizontal permeability ratio, kv/kh, is commonly _________ than 1. |
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Definition
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Term
| What assumptions does that Navier-Stokes equation make? |
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Definition
that density is a function of pressure only
conservation of mass, momentum, and energy |
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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 |
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Definition
| a) the superficial velocity at reservoir conditions |
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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 |
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Definition
| a) near the well for high-rate wells |
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Term
Flow to a well at any pressure is best calculated using
a) pressure
b) potential
c) pressure-squared
d) the spherical flow formula |
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Definition
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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 |
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Definition
| c) usually greater in the vertical compared to horizontal direction |
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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 |
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Definition
| b) the velocity near pore centers |
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Term
The least convergent flow regime is
a) steady state
b) linear flow
c) compressible flow
d) spherical flow |
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Definition
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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 |
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Definition
| c) the arithmetic average |
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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 |
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Definition
| b) lower surface area open to flow |
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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 |
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Definition
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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 |
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Definition
| b) higher for the damaged well in the near well region (s > 0) |
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