Hello,

I am currently performing simulations of a simplified geothermal doublet system consisting of a reservoir and a single fracture.

I am trying to investigate the effect of variations in the aperture/permeability of the fracture, however I am not sure if my implementation is correct because my results do not seem to make sense.

I ran one simulation with no fracture present as a base case. Then, using the relationship permeability, k = a^2/12 (where a is the hydraulic aperture), I ran simulations with 5 values for permeability and the corresponding aperture. I expected that as the fracture permeability decreases toward that of the matrix, the production temperature curves would also shift toward the base case of no fracture. All other variables were kept the same, however when I looked at the temperature curves, they all plotted on basically the same line.

I attached the plot. The matrix case is the dark blue line and all other values show very little variation although the permeability varies over 5 orders of magnitude. I also attached an example of one of the .mmp files because maybe there is something that I am missing.

Cheers,

Ariel

res4_pt3.mmp (638 Bytes)

## ···

From my understanding, the aperture of the fracture is set to $GEOMETRY_AREA in the .mmp file and the fracture permeability set to the keyword $PERMEABILITY_TENSOR.

Hi,

The .mmp file looks ok. Have you checked fluid velocity in the fracture while varying the permeability?

n

## ···

On 06/26/2016 09:10 PM, Ariel Thomas wrote:

Hello,

I am currently performing simulations of a simplified geothermal doublet

system consisting of a reservoir and a single fracture.

I am trying to investigate the effect of variations in the

aperture/permeability of the fracture, however I am not sure if my

implementation is correct because my results do not seem to make sense.

From my understanding, the aperture of the fracture is set to

$GEOMETRY_AREA in the .mmp file and the fracture permeability set to the

keyword $PERMEABILITY_TENSOR.

I ran one simulation with no fracture present as a base case. Then,

using the relationship permeability, k = a^2/12 (where a is the

hydraulic aperture), I ran simulations with 5 values for permeability

and the corresponding aperture. I expected that as the fracture

permeability decreases toward that of the matrix, the production

temperature curves would also shift toward the base case of no fracture.

All other variables were kept the same, however when I looked at the

temperature curves, they all plotted on basically the same line.

I attached the plot. The matrix case is the dark blue line and all other

values show very little variation although the permeability varies over

5 orders of magnitude. I also attached an example of one of the .mmp

files because maybe there is something that I am missing.

Cheers,

Ariel

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Norihiro Watanabe, Dr.-Ing.

Department of Environmental Informatics (ENVINF)

Wissenschaftler

Helmholtz-Zentrum für Umweltforschung GmbH - UFZ

Helmholtz Centre for Environmental Research GmbH - UFZ

Permoserstraße 15 / 04318 Leipzig / Germany

norihiro.watanabe@ufz.de / http://www.ufz.de

Telefon +49 341 235 1806

Sitz der Gesellschaft: Leipzig

Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703

Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus

Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch

Administrativer Geschäftsführer: Dr. Heike Graßmann

I did not check the velocities but I can …I only output the ELE velocities for the base case and for the others I was mainly interested in temperature. I tried to output the velocity at the monitor point as well but this output file returned no values.

I performed similar test with high permeability. In this case I considered several values of permeability log normally distributed around the mean, 8.33e-10. I saw the expected variation in the production profile as can be seen in the attached plot…(blue line is the matrix case). However the same test for a mean of 8.33e-12 showed no spread. I ran around 50 simulations with varying values around the mean and they all plotted on the same line…

Is there some limiting case when the fracture permeability is too close to the medium permeability?

## ···

On Monday, June 27, 2016 at 8:03:51 AM UTC+2, Norihiro Watanabe wrote:

Hi,

The .mmp file looks ok. Have you checked fluid velocity in the fracture while varying the permeability?

n

On 06/26/2016 09:10 PM, Ariel Thomas wrote:

Hello,

I am currently performing simulations of a simplified geothermal doublet

system consisting of a reservoir and a single fracture.

I am trying to investigate the effect of variations in the

aperture/permeability of the fracture, however I am not sure if my

implementation is correct because my results do not seem to make sense.

From my understanding, the aperture of the fracture is set to

$GEOMETRY_AREA in the .mmp file and the fracture permeability set to the

keyword $PERMEABILITY_TENSOR.

I ran one simulation with no fracture present as a base case. Then,

using the relationship permeability, k = a^2/12 (where a is the

hydraulic aperture), I ran simulations with 5 values for permeability

and the corresponding aperture. I expected that as the fracture

permeability decreases toward that of the matrix, the production

temperature curves would also shift toward the base case of no fracture.

All other variables were kept the same, however when I looked at the

temperature curves, they all plotted on basically the same line.

I attached the plot. The matrix case is the dark blue line and all other

values show very little variation although the permeability varies over

5 orders of magnitude. I also attached an example of one of the .mmp

files because maybe there is something that I am missing.

Cheers,

Ariel

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Norihiro Watanabe, Dr.-Ing.

Department of Environmental Informatics (ENVINF)

Wissenschaftler

Helmholtz-Zentrum für Umweltforschung GmbH - UFZ

Helmholtz Centre for Environmental Research GmbH - UFZ

Permoserstraße 15 / 04318 Leipzig / Germany

norihiro...@ufz.de / http://www.ufz.de

Telefon +49 341 235 1806

Sitz der Gesellschaft: Leipzig

Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703

Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus

Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch

Administrativer Geschäftsführer: Dr. Heike Graßmann

Unfortunately the velocity output at particular points is not supported or not reliable in OGS. I normally calculate it from the element velocity using ParaView (extract only fracture elements and then apply "Cell data to point data" filter to get velocity in fractures).

Concerning the temperature breakthrough curve, you will see the fracture permeability influence on it only when heat transport is dominated by advection along the fracture. If flow velocity along the fracture is not sufficiently high, heat conduction in surrounding rocks becomes dominant and you will see no effects with varying the fracture permeability. Heat conduction gets more influence, e.g. when permeability in the fracture is not so high compared to the rock permeability, or the fracture aperture is too small, or thermal conductivity of the rock is high. So if you lower the rock permeability or the rock thermal conductivity, you should be able to see some variations even for a mean of 8.33e-12.

Best,

Nori

## ···

On 27/06/16 15:34, Ariel Thomas wrote:

I did not check the velocities but I can ..I only output the ELE

velocities for the base case and for the others I was mainly interested

in temperature. I tried to output the velocity at the monitor point as

well but this output file returned no values.

I performed similar test with high permeability. In this case I

considered several values of permeability log normally distributed

around the mean, 8.33e-10. I saw the expected variation in the

production profile as can be seen in the attached plot..(blue line is

the matrix case). However the same test for a mean of 8.33e-12 showed no

spread. I ran around 50 simulations with varying values around the mean

and they all plotted on the same line..

Is there some limiting case when the fracture permeability is too close

to the medium permeability?

On Monday, June 27, 2016 at 8:03:51 AM UTC+2, Norihiro Watanabe wrote:

Hi,

The .mmp file looks ok. Have you checked fluid velocity in the

fracture while varying the permeability?

n

On 06/26/2016 09:10 PM, Ariel Thomas wrote:

> Hello,

>

> I am currently performing simulations of a simplified geothermal

doublet

> system consisting of a reservoir and a single fracture.

>

> I am trying to investigate the effect of variations in the

> aperture/permeability of the fracture, however I am not sure if my

> implementation is correct because my results do not seem to make

sense.

>

> From my understanding, the aperture of the fracture is set to

> $GEOMETRY_AREA in the .mmp file and the fracture permeability set

to the

> keyword $PERMEABILITY_TENSOR.

>

> I ran one simulation with no fracture present as a base case. Then,

> using the relationship permeability, k = a^2/12 (where a is the

> hydraulic aperture), I ran simulations with 5 values for permeability

> and the corresponding aperture. I expected that as the fracture

> permeability decreases toward that of the matrix, the production

> temperature curves would also shift toward the base case of no

fracture.

> All other variables were kept the same, however when I looked

at the

> temperature curves, they all plotted on basically the same line.

>

> I attached the plot. The matrix case is the dark blue line and all

other

> values show very little variation although the permeability varies

over

> 5 orders of magnitude. I also attached an example of one of the .mmp

> files because maybe there is something that I am missing.

>

> Cheers,

> Ariel

>

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Norihiro Watanabe, Dr.-Ing.

Department of Environmental Informatics (ENVINF)

Wissenschaftler

Helmholtz-Zentrum für Umweltforschung GmbH - UFZ

Helmholtz Centre for Environmental Research GmbH - UFZ

Permoserstraße 15 / 04318 Leipzig / Germany

norihiro...@ufz.de <javascript:> / http://www.ufz.de

Telefon +49 341 235 1806

Sitz der Gesellschaft: Leipzig

Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703

Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus

Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch

Administrativer Geschäftsführer: Dr. Heike Graßmann

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Norihiro Watanabe, Dr.-Ing.

Department of Environmental Informatics

Helmholtz-Zentrum für Umweltforschung GmbH - UFZ

Helmholtz Centre for Environmental Research GmbH - UFZ

Permoserstraße 15 / 04318 Leipzig / Germany

Telefon +49 341 235 1806

norihiro.watanabe@ufz.de / www.ufz.de

Sitz der Gesellschaft: Leipzig

Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703

Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus

Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch

Administrativer Geschäftsführer: N.N.

Ahh yes that makes sense, I was thinking something along those lines but your articulated much better than I had it in my mind.

Thank you very much.

## ···

On Monday, June 27, 2016 at 5:47:44 PM UTC+2, Norihiro Watanabe wrote:

Unfortunately the velocity output at particular points is not supported

or not reliable in OGS. I normally calculate it from the element

velocity using ParaView (extract only fracture elements and then apply

“Cell data to point data” filter to get velocity in fractures).

Concerning the temperature breakthrough curve, you will see the fracture

permeability influence on it only when heat transport is dominated by

advection along the fracture. If flow velocity along the fracture is not

sufficiently high, heat conduction in surrounding rocks becomes dominant

and you will see no effects with varying the fracture permeability. Heat

conduction gets more influence, e.g. when permeability in the fracture

is not so high compared to the rock permeability, or the fracture

aperture is too small, or thermal conductivity of the rock is high. So

if you lower the rock permeability or the rock thermal conductivity, you

should be able to see some variations even for a mean of 8.33e-12.

Best,

Nori

On 27/06/16 15:34, Ariel Thomas wrote:

I did not check the velocities but I can …I only output the ELE

velocities for the base case and for the others I was mainly interested

in temperature. I tried to output the velocity at the monitor point as

well but this output file returned no values.

I performed similar test with high permeability. In this case I

considered several values of permeability log normally distributed

around the mean, 8.33e-10. I saw the expected variation in the

production profile as can be seen in the attached plot…(blue line is

the matrix case). However the same test for a mean of 8.33e-12 showed no

spread. I ran around 50 simulations with varying values around the mean

and they all plotted on the same line…

Is there some limiting case when the fracture permeability is too close

to the medium permeability?

On Monday, June 27, 2016 at 8:03:51 AM UTC+2, Norihiro Watanabe wrote:

```
Hi,
The .mmp file looks ok. Have you checked fluid velocity in the
fracture while varying the permeability?
n
On 06/26/2016 09:10 PM, Ariel Thomas wrote:
> Hello,
>
> I am currently performing simulations of a simplified geothermal
doublet
> system consisting of a reservoir and a single fracture.
>
> I am trying to investigate the effect of variations in the
> aperture/permeability of the fracture, however I am not sure if my
> implementation is correct because my results do not seem to make
sense.
>
> From my understanding, the aperture of the fracture is set to
> $GEOMETRY_AREA in the .mmp file and the fracture permeability set
to the
> keyword $PERMEABILITY_TENSOR.
>
> I ran one simulation with no fracture present as a base case. Then,
> using the relationship permeability, k = a^2/12 (where a is the
> hydraulic aperture), I ran simulations with 5 values for permeability
> and the corresponding aperture. I expected that as the fracture
> permeability decreases toward that of the matrix, the production
> temperature curves would also shift toward the base case of no
fracture.
> All other variables were kept the same, however when I looked
at the
> temperature curves, they all plotted on basically the same line.
>
> I attached the plot. The matrix case is the dark blue line and all
other
> values show very little variation although the permeability varies
over
> 5 orders of magnitude. I also attached an example of one of the .mmp
> files because maybe there is something that I am missing.
>
> Cheers,
> Ariel
>
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> an email to ogs-users+...@googlegroups.com <javascript:>
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```

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Norihiro Watanabe, Dr.-Ing.
Department of Environmental Informatics (ENVINF)
Wissenschaftler
Helmholtz-Zentrum für Umweltforschung GmbH - UFZ
Helmholtz Centre for Environmental Research GmbH - UFZ
Permoserstraße 15 / 04318 Leipzig / Germany
norihiro...@ufz.de <javascript:> / [http://www.ufz.de](http://www.ufz.de)
```

```
Telefon +49 341 235 1806
Sitz der Gesellschaft: Leipzig
Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703
Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus
Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch
Administrativer Geschäftsführer: Dr. Heike Graßmann
```

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Norihiro Watanabe, Dr.-Ing.

Department of Environmental Informatics

Helmholtz-Zentrum für Umweltforschung GmbH - UFZ

Helmholtz Centre for Environmental Research GmbH - UFZ

Permoserstraße 15 / 04318 Leipzig / Germany

Telefon +49 341 235 1806

norihiro...@ufz.de / www.ufz.de

Sitz der Gesellschaft: Leipzig

Registergericht: Amtsgericht Leipzig, Handelsregister Nr. B 4703

Vorsitzender des Aufsichtsrats: MinDirig Wilfried Kraus

Wissenschaftlicher Geschäftsführer: Prof. Dr. Georg Teutsch

Administrativer Geschäftsführer: N.N.