Abstract:

For low-permeability tight oil/gas reservoirs,economic development is viable only after high-volume hydraulic fracturing which can create multiple fractures and complex network consisting of natural and induced hydraulic fractures.Consequently,fracture arrangement evaluation,prediction of stimulated reservoir volume and well productivity are critical to well stimulation analysis.In combination with the characteristics of tight reservoir and the basics of hydraulic fracture design,we proposed a trillinear flow mathematical model for volume-fractured horizontal wells which can reflect the finite conductivity flow behavior inside hydraulic fractures and massive fractures arrangement.The solution of single fracture at closed boundary condition can be obtained through Laplace transformation.Meanwhile,Stehfest numerical inversion and fracture superposition principle were applied to get formulas of bottom hole pressure and well production for volume-fractured horizontal wells.The model has been valid by using Bakken tight oil production curves.Sensitivity to various para-meters such as fracture arrangement,stimulated reservoir volume,number of fractures have been investigated.The result shows that the pattern of fracture distribution has a great influence on the stimulated reservoir volume;the higher ratio of fracture stage and cluster is,the higher the cumulative oil production of fractured horizontal well is;increasing the numbers of fractures can improve producing efficiency,however,interference between fractures possibly cause the decrease of production.The study results are of great significance for the volume-fracturing design and well productivity evaluation of horizontal wells in tight oil reservoirs.

Key words: fracture arrangement, fractured reservoir volume, volume-fractured horizontal well, trilinear flow model, well productivity prediction