Designing enhanced geothermal and hydraulic fracturing systems based on multiple stages and proppant
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This report consists of two chapters. In the first chapter, designs of Enhanced Geothermal Systems (EGS) with horizontal wells, multiple stages, and proppant are discussed. In EGS, hydraulic stimulation is used to improve well productivity. EGS is typically performed in a nearly vertical well, in one stage, with no proppant. Horizontal wells, multiple stages, and proppant are not used because they are considered not necessary and/or technically infeasible. We found that an EGS design with multiple stages and proppant could give dramatically improved economic performance relative to current designs. We reviewed the literature in order to assess the technical viability of our proposed design. The proposed design would increase cost but deliver substantial improvements in flow rate (and revenue) per well. The second chapter describes a simulation study of proppant transport with Newtonian fluid in a fully three-dimensional hydraulic fracturing simulator, CFRAC. This model has capability to handle proppant settling due to gravity, proppant migration away from the fracture walls, and fracture closure. In the model, the conservation equations of fluid and proppant are sequentially solved in a first-order finite difference scheme. A special algorithm is applied to handle proppant packing due to fracture closure. Our simulation results show good agreement with results from other recently published proppant modeling studies. Sensitivity analysis was performed in order to investigate the effect fluid viscosity, proppant density, and proppant size. Finally, simulations of the tip-screen out (TSO) were performed.