Fracture Modeling

[reisi...@gmail.com]

Dear Peter and Glenn,

I am trying to model a system consisting of a fracture located in the middle of a cement matrix (fracture flow with diffusion into the surrounding cement). I‌ want to track the fracture self-sealing or widening.

I would appreciate your advice on the most appropriate modeling approach for this configuration. In particular, I am wondering:

• Is there an example available for 2D fracture modeling?

• Is the multiple-continuum approach limited to 1D problems, or can it also be applied when the fracture is discretized in 2D?

Thank you very much for your guidance.

Best regards,
Fatemeh

[Hammond, Glenn E]

See my comments below in red.

Glenn

From: pflotra...@googlegroups.com <pflotra...@googlegroups.com> on behalf of reisi...@gmail.com <reisi...@gmail.com>
Date: Sunday, February 22, 2026 at 3:28 PM
To: pflotran-users <pflotra...@googlegroups.com>
Subject: [pflotran-users: 8675] Fracture Modeling

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Dear Peter and Glenn,

I am trying to model a system consisting of a fracture located in the middle of a cement matrix (fracture flow with diffusion into the surrounding cement). I‌ want to track the fracture self-sealing or widening.

I would appreciate your advice on the most appropriate modeling approach for this configuration. In particular, I am wondering:

• Is there an example available for 2D fracture modeling? I know of no simple examples for 2D fracture modeling. We have 3D fracture modeling using Voronoi meshes, but the capability is laborious and the level of complexity is beyond what we can support on a user mailing list.

• Is the multiple-continuum approach limited to 1D problems, or can it also be applied when the fracture is discretized in 2D? All PFLOTRAN simulations are inherently 3D problems (i.e., you have to describe the 3D problem in the GRID card). Multi-continuum can be considered a 4^th dimension off the 3D problem (i.e., in/out of rock matrix).

  https://documentation.pflotran.org/theory_guide/multiple_continuum.html
  With multi-continuum, a single multi-continuum grid cell contains pore space that is split between a fracture volume and a matrix volume (the latter being divided in 1D across cells in the secondary continuum [or the 4th dimension]). Your conceptual model has separate primary continuum grid cells that are assigned as fracture and matrix.

Thank you very much for your guidance.

Best regards,
Fatemeh

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[Fatemeh]

Dear Glenn,

Thank you very much for your comments.

Could you please advise on the most appropriate way to model the configuration shown in the attached image? My goal is to track changes in both the fracture and the surrounding matrix simultaneously. For this reason, I would need to discretize the matrix in both the x and y directions.

As I understand it, in the multi-continuum approach the matrix is represented as a 1D secondary continuum per primary cell, without lateral connectivity between matrix blocks (please correct me if I am mistaken). In that case, would you still recommend using the multi-continuum formulation?

Alternatively, would it be more appropriate to construct an explicit 2D model by assigning a thin set of cells as the fracture (with higher permeability and porosity), similar to an example I found in the PFLOTRAN user community discussions?

Thank you very much for your guidance.

Best regards,

Fatemeh

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/BY3PR09MB7555D4A98FD406B3AB7E33689A77A%40BY3PR09MB7555.namprd09.prod.outlook.com.

[Hammond, Glenn E]

See my comments in red below.

Glenn

From: pflotra...@googlegroups.com <pflotra...@googlegroups.com> on behalf of Fatemeh <reisi...@gmail.com>
Date: Monday, February 23, 2026 at 6:23 PM
To: pflotra...@googlegroups.com <pflotra...@googlegroups.com>
Subject: Re: [pflotran-users: 8682] Fracture Modeling

Dear Glenn,

Thank you very much for your comments.

Could you please advise on the most appropriate way to model the configuration shown in the attached image? My goal is to track changes in both the fracture and the surrounding matrix simultaneously. For this reason, I would need to discretize the matrix in both the x and y directions.

As I understand it, in the multi-continuum approach the matrix is represented as a 1D secondary continuum per primary cell, without lateral connectivity between matrix blocks (please correct me if I am mistaken). In that case, would you still recommend using the multi-continuum formulation? Your description of the secondary continuum is correct. It has a disconnected matrix. If you desire matrix-matrix connectivity (i.e., >1D in the matrix), you must mesh up the matrix explicitly.

Alternatively, would it be more appropriate to construct an explicit 2D model by assigning a thin set of cells as the fracture (with higher permeability and porosity), similar to an example I found in the PFLOTRAN user community discussions? I recommend narrowing the conceptual model below to a single column of grid cells for the fracture. I don’t know that using more than one column of grid cells will improve the accuracy that much as you are using Darcy flow for the fracture. If you are looking to plug the fracture through mineral precipitation, the multi-column conceptual model will likely not form mineral at the interface between the fracture and matrix any more than at the center of the fracture. So, just use one column. Once you develop some intuition with a single column, you can increase the complexity of the conceptual model. It is possible that refinement in the fracture will improve accuracy. But I doubt it will improve your ability to capture reality.

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/CACLNKk4sE%3D9FY_TcZ%3DqyGOMd255i%2B58%2BUmXdC3PZEAAGssz0sw%40mail.gmail.com.

[Fatemeh]

Dear Glenn,

Thank you very much for your prompt response. 

I have a follow-up question regarding fracture sealing.

In the PFLOTRAN, is there a way to capture preferential mineral precipitation near the fracture–matrix interface (i.e., precipitation depth across the fracture walls)?

I am trying to understand this process can be represented meaningfully in PFLOTRAN, or whether this would require a different modeling approach.

Thank you very much for your guidance.

Best regards,
Fatemeh

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/BY3PR09MB7555C9146B2DFC23721AD3EC9A74A%40BY3PR09MB7555.namprd09.prod.outlook.com.

[Hammond, Glenn E]

Mineral precipitation can only occur within a cell. Therefore, cells at the fracture-matrix interfaces (assuming you have assigned fracture/matrix to primary continuum grid cells) will experience preferential mineral precipitation if the surface area and affinity factor (a function of species concentration) favor precipitation in those regions. For example, in a calcite precipitation scenario, you could load the matrix with calcium and the fracture with high pH carbonate, resulting in calcite precipitation at the interface. However, this approach involves manipulating the system.

Glenn

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[Fatemeh]

Thank you very much Glenn.

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/BY3PR09MB7555797C5AF6A868318AACE89A75A%40BY3PR09MB7555.namprd09.prod.outlook.com.