Simulation Study On Volumetric Fracturing Capacity Of Horizontal Wells In Tight Reservoirs

China has tremendous unconventional tight oil resources which are widely distributed in lots of petroliferous basins. The exploiation of tight oil has important strategic meaning to remit energy sources shortage, change energy sources structure and guarantee energy sources security. However, the storage space in tight oil reservoir is mainly nanoscale connected pore throat, difficult to meet the needs of economic development. The effective way to realize effective exploitation of tight oil reservoir is "horizontal well+volume fracturing", which can creat complex fracture network and realize the comprehensive transformation of reservoir in three-dimensional direction. This technology increases the contact area between fracture faces and reservoir, improves the seepage condition and then achieves industrial oil flow. In order to maximize the exploitation profit, it's necessary to optimize fracturing design and predict production after volume fracturing. Due to the micro fractures generally development in tight oil reservoir, fracture extension is affected by natural fracture distribution and the existing process, which makes the geometry of fracture networks very complex, resulting in extremely complex fluid flow progress. At present, the most of existing productivity models of volume fracturing all simplify the distribution of natural fractures as well as the geometry of fractures network, which can't completely reflect the reality. Therefore, volume fracturing production prediction for horizontal well in tight formation is needed to perfect and develop.Embarking from the basic principle of seepage flow mechanics, according to the tight reservoir geological characteristics as well as considering the actual situation of fracture network, a volume fracturing productivity prediction model was established. This model was based on the equivalent continuous model of fractured medium, and was solved with finite difference method. The mathematical model with full tensorial permeability also took start-up pressure gradients and pressure sensitivity into account; it can simulate all kinds of irregular fractures effects on production performance.Numerical simulation researches were carried out for both orthogonal network and non-orthogonal network in this paper. Series of varying parameters of formation and fracture network were preseted to simulate production performance, and then optimized the volume fracturing design program and predicted the productivity. Different influence factors of fracturing effect were discussed, including fracture distribution schemes, fracture length, fucture density, fracture aperture and formation permeability, etc. Meaningful conclusions were drawn after comparative analysis of simulation results, which provided a theoretical guidance for the on-site fracturing operation.