Tight and shale reservoirs are characterized by ultra-low permeabilities that impede the fluids to naturally flow from the reservoir to the wellbore. In such reservoirs horizontal multi-fractured wells are very common to produce at high initial rates to make the reservoir development economical. Numerical Modeling of this type of wells is time consuming since it requires a very refined grid to capture the early transient behavior. Analytical tools are currently used to calibrate and forecast performance for such wells because they mainly produce single phase hydrocarbons. These tools assume homogeneous reservoirs with equally spaced and similar geometry fractures, which imply average fracture dimensions and reservoir properties. Despite simplicity, analytical solutions have some errors in the averaging method that may over-predict the future potential of these horizontal multi-fractured wells. This brings the need to determine the most accurate method to average fracture dimensions and reservoir permeability to calibrate performance and accurately predict future potential. Results using the proposed permeability averaging method in multilayer cases are also presented in this paper.
In this paper several averaging methods are discussed to account for areal and vertical heterogeneity using synthetic numerical models with varying fracture dimensions and reservoir permeability. Results using average properties are compared to those from " full-fractured" models. Type curves are derived from the difference in results from both models, depending on fracture spacing, reservoir permeability and fracture geometry. It is also shown that the commonly used kh average to upscale well's productivity does not properly reproduce the multilayer effects during transient flow. Under these conditions, a more robust permeability average is proposed that not only depends on the flow capacity but also on the conductivity-storability ratio of each layer.