401 Final

Front 1

What are the three types of equations that are combined to form the partial differential equation for fluid flow in porous media?

Back 1

conservation of mass
flow equation (darcys law)
and equation of state

Front 2

The peaceman well flow equation for reservoir simulation relates what?

Back 2

Well flowing bottom hole pressure, grid block pressure, and well flow rate

Front 3

What is the relation between water flooding efficiency and the vertical permeability distribution that is Kv/Kh?

Back 3

for waterflooding to work theres needs to be a high Kv/Kh so that water can flow up instead of sweeping a layer and keeping the oil in that layer

Front 4

At critical rate for coning, what reservoir forces are equal?

Back 4

gravity and viscous forces

Front 5

What does IMPES mean? How is it used to solve the system of porous media flow?

Back 5

Implicit Pressure and Explicit Saturation. We use it to implicity solve for presure and a second explicit equation to solve for saturation to reduce time and memory needed to solve the system of porous media flow.

Front 6

What are the stability characteristics for implicit and explicit equations?

Back 6

explicit = unstable at large delta T
implicit = unconditionally stable

Front 7

During the entire reservoir simulation time span, the timesteps are always kept constant due to its simplicity (t/f)

Back 7

false

Front 8

When someone uses the restart option in a reservoir simulator, the simulator stops the simulation att some specified time, save the last result and set it as initial condition to the next time it will run (T/F)

Back 8

True

Front 9

In this class we used ECLIPSE as the main reservoir simulator and for production optimization in the waterflood lab (T/F)

Back 9

False

Front 10

Although we use reservoir and well properties in designing the simulation grid, the simulation grid is independent of the reservoir and well properties (T/F)

Back 10

true

Front 11

What are the most 5 sources of simulation errors ranked from most uncertain to least uncertain?

Back 11

1) innaccurate reservoir description
2) truncation error
3) Instability
4) Roundoff error
5) Model approximation

Front 12

Why might an orthongal model have a greater recovery per water injected than a parallel model?

Back 12

If the orthogonal model has a straight path to the wells it is less tortous, allowing for better flow.

Front 13

What is history matching?

Back 13

the process of adjusitng the reservoir description until the production and reserves predicted by the dynamic model match the historical production and reserves

Front 14

In a single phase reservoir with only one well, if you constraint the well in the reservoir simulation by well rate, that is, use the same well rate as in the measurement data, you would expect the history match the differences in bottom hole pressure (T/F)

Back 14

True
(constant q -> match BHP
constant BHP -> match Q)

Front 15

In history matching, the slope of the bottomhole pressure curve vs time in a linear time axis is inverserly proportional to permeability whereas the slope of the curve in a semilog plot is inversely proportional to the drainage area (T/F)

Back 15

False
(Perm -> linear portion of semilog plot
Drainage area -> linear portion of cartesian plot)

Front 16

Can symmetry be used every time? (T/F)

Back 16

False

Front 17

In field wide history matching, the best practice is to follow the squence:
A. Match gross Reservoir behavior
B. Match detailed reservoir behavior
(T/F)

Back 17

True

Front 18

In order to match the gross reservoir behavior, describe the sequence of tasks to be performed

Back 18

I) match gross reservoir behavior
match average pressure
match F(a,h,porosity, Sw) + K
match constant movements and build ratios
II) match detailed reservoir behavior
(match regional performance, match individual well performance aka F(a,h,porosity,Sw) + skin)
III) continue to monitor reservoir performance

Front 19

What is included in Well data?

Back 19

Completion data
production and injection data
pressure data (static and flowing)
operational control and constraint information
wellstring and gathering system data

Front 20

The 1-D diffusitivity PDE (in Field units) show above is nonlinear because?

Back 20

Some coefficients of dp/dx are functions of the dependent variable p

Front 21

The diffusitivy equation in radial coordinates is shown below. What are the initial and boundary conditions to solve this PDE?

Back 21

Front 22

What is the type of the finite difference formulation?

Back 22

Central

Front 23

What is the type of finite difference formulation?

Back 23

Backwards

Front 24

What is the type of finite difference formulation?

Back 24

Forwards

Front 25

The forward difference approximation to vole for a new time level pressure and central difference approximation to solve for space derivatives in the flow equation (shown) results in what type of calculation procedure?

Back 25

Explicit

Front 26

The backward difference approximation to solve for a new time level pressure and the central difference approximation to solve for space derivatives in the flow equation (shown) results in what type of calculation procedure?

Back 26

implicit

Front 27

What two reservoir forces are in equilibrium prior to production from a reservoir?

Back 27

gravity and capillary

Front 28

The best way to determine if a numerical solution is stable is to make runs with different time step sizes and note the difference in results (T/F)

Back 28

True

Front 29

Grid orientation effect is most severe for fluid displacement at low mobility ratios (T/F)

Back 29

False

Front 30

To have consistent 3- phase relative permeability data, oil relative permeability should be the same value in the two sets of 2 phase relative permeability data at what saturation conditions?

Back 30

Sg= 0
Sw= Swc

Front 31

Briefly state the primary advantage and disadvantage of iterative methods for solving the matrix equation Ax=d that results from implicit solution of the simulation equations

Back 31

Ad -> do not have to store the entire matrix
Dis -> multiple calculations/passes to get solution

Front 32

List the minimum set of reservoir property maps (array data) that must be entered for CMG to be able to execute

Back 32

Grid top
Grid thickness
Porosity
Permeability

Front 33

The equivalent radius, Ro, in the peaceman flow equation is a function of the grid block dimensions and the grid block porosity (T/F)

Back 33

false

Front 34

One of the disadvantages of gradient based automatic history matching algorithms is that they can get trapped in local minima (T/F)

Back 34

True

Front 35

When should automatic history matching algorithms be terminated?

Back 35

Sum of squared errors is not decreasing
Parameter estimates are not changing significantly

Front 36

Name the two major ranking criteria used to select which reservoir parameters to vary in history matching performance with a reservoir simulator. In other words, parameters to change should be high on both of these lists.

Back 36

Uncertainty
sensitivity

Front 37

In history matching field wide, multiphase reservoir performance: What observed pressure values should be matched first?

Back 37

Field wide average pressure

Front 38

In history matching field wide, multiphase reservoir performance, what type of rate constraint should be used in matching these first pressure vales?

Back 38

total fluid

Front 39

In history matching field wide, multiphase reservoir performance, what parameter(s) should be varied to match these first pressure values?

Back 39

Reservoir volume
total compressibility
aquifer volume

Front 40

In history matching field wide, multiphase reservoir performance,
What observed pressure values should be matched last?

Back 40

Individual well flowing BHP

Front 41

In history matching field wide, multiphase reservoir performance, what parameter(s) should be varied to match these last pressure values?

Back 41

skin factor or well index

Front 42

A good history match is a necessary condition for an accurate future performance project (T/F)

Back 42

True

Front 43

A good history is a sufficient condition for an accurate future performance projection (T/F)

Back 43

False

Front 44

Define net pay thickness

Back 44

The total sand that contains hydrocarbons

Front 45

Define gross thickness

Back 45

The total thickness of a layer

Front 46

Define net sand

Back 46

The total thickness of a reservoir

Front 47

Briefly describe how you would calculate net pay, gross thickness, and net sand from well log data

Back 47

Gross thicness is the top of the formation from the bottom of the formation
Net sand is the addition of each layers in the formation
Net pay is the sum of the sand with hydrocarbons

Front 48

Which do you use in reservoir simulation? Gross Thickness, Net Pay, Net Sand

Back 48

Gross Thickness