NTNU

SIMULATION EXAPLES OF WATER INJECTION

NTNU

Author: Professor Jon Kleppe

Assistant producers:

Farrokh Shoaei

Khayyam Farzullayev

Simulation Examples of Water Injection

REFERENCES ABOUT EXIT

Five spot model, water injection simulation

Case 1

Coarse grid model

Case 2

Fine grid model

Effect of permeability distribution

Case 1Permeability increases

downwards

Case 2Permeability decreases

downwards

The water can apparently travel through a coarse grid model more quickly than a fine grid model.

The water front becomes smeared causing a prematurely water break through in the coarse grid model.

This effect is called numerical dispersion.

In practice there are other factors contributing to numerical dispersion such as the averaging of relative permeabilities and of saturations.

Characteristics of this model:

A simple quarter five-spot model of oil displacement by water injection.

The oil producer well at the corner was controlled by constant bottom hole pressure (BHP) and the water injector well at the centre was controlled by constant injection rate.

Case 1 : geometry of 5 x 5 x 1

Case 2 : geometry of 50 x 50 x 1





Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Case 1

Animation of Oil Saturation

5 x 5 x 1




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

The movement of water front through the model can be seen better in this view.

Animation of Iso-Surface Oil Saturation




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards


The model structured with large number of gridblocks would be an obvious way to overcome the inaccuracy of numerical dispersion.

Case 2

50 x 50 x 1




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Animation of Iso-Surface Oil Saturation

In the case with a large number of grids we achieve better sweep efficiency and sharper developed front.




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards


As a result of gravity forces, the heavier fluid flows downwards. Since the density of water is normally greater than oil’s, it will always tend to flow to the layers below.

As a general rule of fluid flow in porous media, fluids always flow to the higher permeability layers.

Characteristics of this model:

Two-phase cross-sectional linear simulation model

Geometry: 50 x 1 x 10

Water injection well is located on the left side of the model

Producer is on the right hand side of the model.

Case 1 : Permeability increases downwards

Case 2 : Permeability increases upwards




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Case 1 The injected water tends to flow towards the bottom layers as a result of

gravity and increase of permeability downwards, this leads to early water break through.


Permeability increases downwards




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Water mass flow

As the water displaces oil from the bottom layer, it may leave some zones not displaced due to fast movement of water along the bottom towards the producer well.




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Case 2 The injected water tends to be in the upper layers because of the high

permeability.

On the other hand, gravity also plays its role by pushing the water downwards

The effect of both factors create balance in the sweep of the reservoirAnimation of Oil Saturation

Permeability decreases downwards




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Water mass flow

From this diagram it is possible to see the movement of water to the bottom by gravity from the top layers, while displacing oil.




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Oil saturation profile, highest permeability layer at bottom.

Oil saturation profile, highest permeability layer at top.

Water sweeps the oil with greater efficiency in Case 2 than in case 1.

In this slide both examples discussed before are simulated at the same grid distribution and time interval in order to illustrate the difference in sweep efficiency.




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

References

Kleppe J.: Reservoir Simulation course

Snyder and Ramey: SPE 1645




Case 1

Coarse grid model

Case 2

Fine grid model



downwards


downwards

Title: SIMULATION EXAPLES OF WATER INJECTION

Author: Name: Prof. Jon Kleppe

Address:NTNU

S.P. Andersensvei 15A

7491 Trondheim

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