The invention is a method for optimizing the development of a fluid reservoir using a fractured medium mesh generated from a first-order balanced octree technique is disclosed. A mesh of a discrete fracture network generated by defining a set of cells for each fracture and then a mesh of the matrix medium is generated by dividing each cell by an octree technique, wherein a cell is divided into eight cells. The transmissivities between the cells of the fracture mesh, transmissivities between the cells of the matrix medium mesh and transmissivities between cells of the fracture mesh and cells of the matrix medium mesh are then determined. Finally, the cells and the transmissivities are used for generating an image of the fluid reservoir from which the development of the fluid reservoir is optimized.
