Modeling naturally fractured reservoirs (NFR) is regaining interest in the industry and academia thanks to the revolution in unconventional hydrocarbon and EOR in carbonate fractured reservoirs. This course provides an overview of naturally fractured reservoirs (NFR) and focuses on traditional and advanced methods to model NFR. The course includes: 1) Introduction on NFR: definitions, importance, detection methods, characterization; 2) Single porosity model: multiphase flow, matrix fracture interaction (diffusion, imbibition, infiltration), gridding, limitations; 3) dual porosity/dual-permeability models: derivations, shape factor, transfer functions, limitations; 4) Discrete fractured models; 2D/3D gridding simplifications; S)Advanced methods; Finite Element (FE), Control-Volume FE, Mixed FE; 6) DFN upscaling: static/dynamic upscaling, single-phase/multi-phase upscaling. Note: students are expected to have at least basic familiarity with: Multi phase flow in porous media, and programming in Matlab or Python