Naturally fractured oil and gas beds display a nonlinear behaviour under their development. Within the framework of a nonlinear model by Buyevich and Nustrov effective porosity and permeability coefficients of fractured beds can decrease significantly when the reservoir pressure falls down. In the paper nonisothermal filtration processes are considered on the base of this model. Hot fluid injection is used with the purpose of oil recovery increase. Self-similar and numerical solutions are obtained. For example, in the case of instantaneous source the heat is localized in a fixed region. In the general case temperature fields change more sharply than pressure ones. Main temperature changes occur near the well. Temperature waves lag behind from pressure waves. In a linear formation all perturbations evolve more uniformly. When a gas well is put into operation with a fixed production rate temperature changes are generated in a bed. A self-similar solution of governing equations is obtained in the case when the gas viscosity depends insignificantly on the temperature. In the general case computational modelling of the equations is performed. It has been found that the similarity of temperature and pressure fields depends on the nonlinearity of the system. The similarity occurs only in the linear case.