Numerical scheme to simulate flow through anisotropic rocks in TOUGH2

•We have implemented in TOUGH2 and tested a new scheme to deal with anisotropic permeabilities.•With the new scheme the axes of the anisotropy can be oblique to the connections between grid blocks.•We have tested the program against the analytical Theis solution for anisotropic transmissivity.•We have tested the program against another groundwater flow program (Aqua3D).•We also have tested our program with various meshes: hexagonal, rectangular and irregular.

A new numerical scheme for fully tensorial treatment of anisotropic flow within model layers (2D) has been designed and implemented into the TOUGH family of simulators. The new scheme has been rigorously tested against a simple theoretical solution to Darcy's law as well as a more complicated example solved by numerical software packages with anisotropic flow capabilities. In all cases, a good agreement with the new scheme has been found.