Research On The Theory And Analysis Of Well Test For Multiple-Fractured Horizontal Well In Complex Oil And Gas Reservoirs

Energy is the material basis of human activities. The increasing energy demand and energy pressure have raised our concerns on some unconventional oil and gas resources like tight oil and gas reservoirs, multi-media carbonate reservoirs and shale gas reservoirs. However, vertical wells and horizontal wells can not meet the requirements of efficient resources development due to the low porosity, low (ultra-low) permeability, high flow resistance and poor connectivity of these oil and gas resources. In contrast, multistage fracturing which produces multiple fractures and increases the drainage area can improve the productivity. Thus, multiple-fractured horizontal well has become an inevitable choice for developing such reservoirs. At present, the multiple-fractured horizontal well technology is increasingly mature and has been applied to a large number of domestic oilfields. However, the backward porous flow theory as well as the vague understanding of the fracture network porous flow rules and bottomhole pressure dynamic change rules after multiple-fractured lead to the shortage of theoretical basis about how to efficiently develop the horizontal well after fracturing.Based on the fundamental theory of mechanics of flow through porous media, according to the practical geological traits of tight reservoirs, multi-media carbonate reservoirs and shale gas reservoirs, a series of flow models of multiple-fractured horizontal wells are established, and these models consider practical features of fractures in the strata such as unequal distance between the neighbor fractures, unequal half-length and half-height of each fracture and unequal arbitrary angle. The mathematical models are solved using the theory of point source function and the method of orthogonal transformation, and then the pressure dynamics curves are plotted through computer programming. Besides, the sensitivity characteristics of changing formation parameters and well parameters which affecting the type curves are analyzed thoroughly. The main models are as follows:? Three porous flow models of multiple-fractured horizontal wells in tight sandstone gas reservoirs (infinite conductivity fractures, finite conductivity fractures, two-zone linear composite) are established;? Seven porous flow models of multiple-fractured horizontal wells in multi-media carbonate reservoirs(fractured, porous-vuggy, fractured-vuggy carbonate formations) are established;? Three porous flow models (pseudo-steady diffusion model, transient diffusion model, two-zone linear composite model) of multiple-fractured horizontal wells in shale gas reservoirs are established.. In the end, a systematic complex porous flow theory and well test analysis method for multiple-fractured horizontal wells are obtained. What's more, real case analysis is carried out for four multiple-fractured horizontal wells, and some useful fracture parameters and reservoir parameters are derived. The research results will provide some new porous flow models for the study of tight reservoirs, multi-media carbonate reservoirs and shale gas reservoirs, promote the development of the mechanics of flow through porous media, and lay the theory foundation for efficient development of horizontal wells after multistage fracturing.