--> Damage Model for Reservoir With Multisets of Natural Fractures and its Application in Hydraulic Fracturing Simulation

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Damage Model for Reservoir With Multisets of Natural Fractures and its Application in Hydraulic Fracturing Simulation

Abstract

Description The continuum damage method is an effective measure for simulation of fracture development caused by stimulation injection. Natural fractures existing in reservoir formations have an important impact on stimulation-induced damage evolution. This work establishes a numerical procedure for the calibration of a damage model with measured information of natural fractures multisets. Image logging data is used. The synthetic value of the damage variable was derived with the work-equivalence principle for the modeling of natural fracture multisets. An example of the procedure illustration is presented. Application The proposed procedure was used to determine the initial value of scalar continuum damage variable of a tight sand reservoir with three sets of natural fractures, and it was further applied during a simulation of hydraulic fracturing of a zipper frac of two horizontal wells in a tight sand oil formation. Results and Conclusions Three sets of natural fractures were identified from image logging data of the given tight sand reservoir formation. There is a value of damage variables for each set of natural fractures. The synthetic value of damage variables was derived, which represent effects of these three sets of natural fractures. Numerical results of the 3D-coupled hydro-mechanical finite element simulation on the zipper frac are presented, which include the (1) contour of initial damage field, (2) total damage distribution between two injection stages after stimulation, (3) distribution of pore pressure and maximum principal strain components, (4) and comparison of damage distribution and stimulated formation volume for two different injection measures. Significance This work provides a workflow for modeling reservoir hydraulic fracturing with multisets of natural fractures using the continuum damage method. Also, it shows that the coupled hydro-mechanical finite element model is an effective tool for estimating stimulated volume in tight sand reservoirs.