Fracture Treatment Simulations Using a Modified Discrete Element Model (MDEM)
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Hydraulic fracturing is a widely used well-stimulation technique and one of the primary engineering tools for enhanced well productivity. To improve the understanding of how untouched rock mass reacts to stimulation, SINTEF Petroleum Research has developed a simulator called Modified Discrete Element Method (MDEM). In this thesis, MDEM simulations are compared to literature and established truths to better understand the mechanisms in the reservoir. The main focus will be on investigating the effects of natural fractures and shear-dilation during fracture treatments. Both features are known to increase the stimulated area. After fracture treatments, shear-dilation can also help in maintaining the enhanced conductivity. Numerical studies have been conducted to look at fracture propagation in naturally fractured reservoirs and the final effect of shear-dilation on fracture treatments. Also, an attempt was done to mimic altered fluid viscosity in the simulator, and fall-off tests were carried out to investigate the possibility of using MDEM to estimate fracture properties. The direction of natural fractures, both on a global (meters) and a local (centimeters) scale, showed to have great impact on the induced fractures half lengths. Natural fractures must therefore be taken into account when fracture stimulations are planned. Shear-dilation showed little relative effect on fracture aperture during injection, but was found to be of great importance after the treatment was ended and the fractures had closed.