A NUMERICAL WELL TEST MODEL FOR MULTI-FRACTURED HORIZONTAL WELLS BASED ON DISCRETE-FRACTURE MODEL AND ITS APPLICATION

Horizontal well fracturing technology has become a key technology in the development of low permeability oil and gas reservoir, shale gas and tight gas and other unconventional reservoirs. This paper developed a numerical well test model for multi-fractured horizontal wells based on discrete-fracture model which simplifies the fractures as lines. The finite element method was applied to solve the mathematical model and get the type curves and pressure profiles. The log-log type curve of bottom hole pressure can be divided into seven stages: wellbore storage, fractures linear flow, fractures-formation bilinear flow, fractures interacting flow, formation linear flow, radial flow, and boundary domain flow. Among them, the fractures-formation bilinear flow and fractures interacting flow are the two typical features. The effect of fractures’ numbers, distance of fractures, asymmetry of fractures, fractures with unequal length, and some fracturing failure on the transient pressure and derivative responses were also studied. The analysis results showed that the number of fractures and the spacing between fractures have the greatest influence on the type curves. More fractures, fractures with larger distance, symmetrical fractures with equal length were propitious to reduce the flow resistance of bottom hole and increase production capacity. The multi-fractured well test model proposed in this paper was applied in the interpretation of build-up tests of multi-fractured horizontal wells. The results of a field case in Sichuan Basin shown that the model matched with the tested data very well. The developed numerical well test model can be used to obtain the parameters of reservoirs and fractures, and to provide technical support for the design and evaluation of hydraulic fracturing.