1. FraC: a DFN conforming meshing approach used to obtain reference simulations for steady-state flow, transport and well-test simulations
T-D. Ngo, A. Fourno, B. Noetinger
IFP Energies Nouvelles, 1 & 4 avenue du Bois Préau, Rueil-Malmaison France
Abstract: Modeling steady-state flow, transport and well-test simulations in fractured media is a numerical challenge. That is due to the geometrical complexity of the discrete fracture network (DFN) and to the input data uncertainties. A FraC approach has already been tested and validated for simulating steady-state flow and transport processes [1]. This work presents some new results for well-test simulations run on FraC meshes. A classical regular fracture network and a complex fracture network from the synthetic Bloemendaal reservoir will be considered. The Bloemendaal field is a 12 ×15 km oil saturated carbonate reservoir that consists in a North/South oriented anticline structure characterized by 3 units, 3 rock types and 3 diffuse fracture sets. In the Bloemendaal reservoir faults are also known to be transversal barriers for fluids. In addition these faults are suspected of being longitudinal drains, which can be modeled using fault-related fractures. Our preliminary results emphasize the effect of these faults on well-test analysis.
Well
Reservoir
DFN model
Objective: Numerical simulations for steady-state flow, transport and well-test on high-resolution 3D DFN meshes.
FraC idea: to decompose each discrete fractures into a set of connected closed contours including each fracture intersection segments. Special focus is put on common fracture boundaries ensuring accurate conforming triangulation. The advantages of the FraC approach is, that the resulting meshes closely respect the DFN geometry and the topology of the intersecting fracture networks.
FraC strategies to model fracture intersections:
Moving existing points (S1) or Adding new points (S2)
Transport numerical benchmark ([1],[2])
(S1)
(S2)
Well-test validation on a regular DFN
(using analytical solution [3])
First results on the Bloemendaal reservoir
DFN mesh
Pressure (~100Bars) ΔP
Pressure (~100Bars)
𝐭 𝛛𝐏 𝛛𝐭
Time (s)
Lx (m)
Ly (m)
Lz (m)
1000
100
Spacing (m)
Conductivity (mD.m)
Aperture (m) 20
250
0.1
Q (m3.s-1)
Pini (Bar)
KH-3D mD.m
KH-2D mD.m
1574
1250
Transmissivity ΔP
𝐭 𝛛𝐏 𝛛𝐭
Time (s)
Conclusion and perspectives : the FraC approach (associated to LaGriT and Dumux open source software) was validated using a transport simulation benchmark ([1], [2]) and transient pressure analytical solution. Applications to the Bloemendaal reservoir are also presented. The next step is to take the matrix into account and to extend the approach to fractured and karst reservoirs.
[1] Ngo, T. D., Fourno, A., Noetinger, B., Modeling of transport processes through large-scale discrete fracture networks using conforming meshes and open-source software. Journal of Hydrology 254, 66–79.
[2] Ahmed, R., Edwards, M.G., Lamine, S., Huisman, B.A., Pal, M., Three dimensional control-volume distributed multi-point flux approximation coupled with a lower-dimensional surface fracture model. J. Comput. Phys. 303, 470–497
[3] Chaumet P., Cours de production tome III. Ecoulements monophasiques des fluides dans les milieux poreux. Editions TECHNIP, pages
[4] Los Alamos Grid Toolbox, Los Alamos National Laboratory. URL:
[5] DuMux, Web site for the computer code DuMux. URL: