Improved Three-dimensional Three-phase Natural Fractured Reservoir Simulation Model

Naturally fractured reservoir is an important kind of hydrocarbon reservoirs, which contains more than twenty percent of the world's oil and gas reserve. But because of the complex fracture networks exist in these reservoirs that can greatly influence the porosity, permeability and flow behavior of the fluids, they are difficult to be developed effectively. Meanwhile, the present of fracture networks also has certain influence on the ultimate recovery rate of these reservoirs. There are so many naturally fractured reservoirs in the west region of our country which have been proved to contain considerable amount of reserve that it is greatly significant for the petroleum industry of China and even of the whole world to go a step forward for reorganization of the flowing mechanism of naturally fractured reservoirs, and improve the accuracy of their numerical simulation to provide reliable predicted information for the effective recovery of such reservoirs.To the present, many scholars have done a great deal of laboratory researches on the recovery mechanisms of naturally fractured reservoirs, including convection, dissolved gas drainage, gravity drainage, imbibition and block-to-block effect, etc., and put out some basic concepts. Thus, the study on the three-phase flow in the porous media mechanisms between the fracture and matrix blocks are gradually deep-going and complete. Reservoir numerical simulations and laboratory experiments are mutually supplementary and verifying on the mechanism study of naturally fractured reservoirs. Many researchers carried out numerical simulations on various presumptions and for different one or several effective mechanisms so as to better understand the roles and influences of every factor contained in these mechanisms. In recent years, with the development of deep-going laboratory studies and great amount of practical simulations, the simulators of naturally fractured reservoirs have been improved and completed. The factors considered in these simulators are more and more comprehensive, and the simulation results are closer to the realistic situations of the objective reservoirs.According to the predecessors' research achievements, and on the base of the flowing laws and recovery mechanisms, the most important and difficult point for the simulations of the fractured reservoirs-accurate description of fracture-matrix interflow rate is emphasized in this dissertation. Several common interflow models are introduced, which are single-block, Warren-Root, Kazemi, Tomas and Litvak model. After analyzing of the influences of different mechanisms on the interflow terms, a improved fracture-matrix interflow model is put forward and the corresponding three-dimension, three-phase fractured reservoir simulator isalso developed. Thus, a complete set of theories and methods for the development and prediction of naturally fractured reservoirs is formed. It is not only an extension to the theories and methods of numerical simulation of naturally fractured reservoirs, but also has certain important guiding significance for the accurate prediction and improvement of the ultimate recovery rate of such reservoirs.