Browsing by Subject "Hydraulic fracturing simulation"
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Item Diagnosis of induced hydraulic fractures during polymer injection(2015-05) Ma, Yiwei, M.S.E.; McClure, Mark W. (Mark William); Balhoff, MatthewPolymer transport with complex fluid rheology was implemented into an existing hydraulic fracturing simulator (CFRAC), and the implementation was extensively validated. Shear thinning viscosity was included for polymer fluid flow in both porous media and fractures. Shear thickening viscosity was implemented for flow in the matrix. Polymer injections were simulated to investigate the effect of polymer rheology, including both shear thinning and shear thickening behaviors, on polymer injectivity and on the possibility of induced hydraulic fracturing. The results indicated that shear thickening decreases injectivity and can induce initiation of hydraulic fractures. The hydraulic fractures substantially enhance injectivity, and eliminate the reduction in injectivity due to shear thickening. Pressure fall off tests were simulated to study the effect of polymer rheology on the identification of hydraulic fractures from the shut-in transient after shut-in. The results showed that standard methods from pressure transient analysis can be applied to diagnose the presence hydraulic fracturing by identifying a linear flow regime and fracture closure on a Bourdet derivative plot and a square root of time plot. It was found that these methods are effective regardless of shear thickening and shear thinning rheology. However, the results suggested that if the fracture is small and closes quickly, this could cause difficulty for the diagnosis.Item Integration of microseismic data with geomechanical model(2015-05) Yang, Mingyuan, M.S.E.; McClure, Mark W. (Mark William)Hydraulic fracturing is a technology that is applied to increase production from unconventional resources such as shale gas and tight oil. Many hydraulic fracturing models have been developed in recent years that can be used to predict the performance of a hydraulic fracturing treatment. Inverse modeling involves conditioning simulation models to field data. The solution to the inverse problem provides estimates for formation properties and other model input parameters. The tuned model can then be used for predictive simulations. In this research, we developed a framework that can solve inverse problems using a Gibbs sampler and a radial basis function proxy model. In multidimensional inverse problem, the solution is often not unique, which means that there are multiple combinations of input parameters that can provide matches to the data. The goal of this research is to find a practical algorithm that can find all possible parameter combinations that match the available data, within bounds specified by the user. This is better than obtaining a single solution that matches the data, because it allows us to better account for uncertainty. For finding precise matches to data, our algorithm would be outperformed by other methods. However, our algorithm is very good at efficiently mapping out the global solution space and solving highly nonunique problems. The framework that we propose also allows us to visualize the relationship between input variables in order to better understand the underlying physical processes. In this report, two example cases are presented and discussed. The example cases demonstrate the efficacy of our approach.Item Numerical Modeling of Hydraulic Fracture Propagation Using Thermo-hydro-mechanical Analysis with Brittle Damage Model by Finite Element Method(2013-07-16) Min, KyoungBetter understanding and control of crack growth direction during hydraulic fracturing are essential for enhancing productivity of geothermal and petroleum reservoirs. Structural analysis of fracture propagation and impact on fluid flow is a challenging issue because of the complexity of rock properties and physical aspects of rock failure and fracture growth. Realistic interpretation of the complex interactions between rock deformation, fluid flow, heat transfer, and fracture propagation induced by fluid injection is important for fracture network design. In this work, numerical models are developed to simulate rock failure and hydraulic fracture propagation. The influences of rock deformation, fluid flow, and heat transfer on fracturing processes are studied using a coupled thermo-hydro-mechanical (THM) analysis. The models are used to simulate microscopic and macroscopic fracture behaviors of laboratory-scale uniaxial and triaxial experiments on rock using an elastic/brittle damage model considering a stochastic heterogeneity distribution. The constitutive modeling by the energy release rate-based damage evolution allows characterizing brittle rock failure and strength degradation. This approach is then used to simulate the sequential process of heterogeneous rock failures from the initiation of microcracks to the growth of macrocracks. The hydraulic fracturing path, especially for fractures emanating from inclined wellbores and closed natural fractures, often involves mixed mode fracture propagation. Especially, when the fracture is inclined in a 3D stress field, the propagation cannot be modeled using 2D fracture models. Hence, 2D/3D mixed-modes fracture growth from an initially embedded circular crack is studied using the damage mechanics approach implemented in a finite element method. As a practical problem, hydraulic fracturing stimulation often involves fluid pressure change caused by injected fracturing fluid, fluid leakoff, and fracture propagation with brittle rock behavior and stress heterogeneities. In this dissertation, hydraulic fracture propagation is simulated using a coupled fluid flow/diffusion and rock deformation analysis. Later THM analysis is also carried out. The hydraulic forces in extended fractures are solved using a lubrication equation. Using a new moving-boundary element partition methodology (EPM), fracture propagation through heterogeneous media is predicted simply and efficiently. The method allows coupling fluid flow and rock deformation, and fracture propagation using the lubrication equation to solve for the fluid pressure through newly propagating crack paths. Using the proposed model, the 2D/3D hydraulic fracturing simulations are performed to investigate the role of material and rock heterogeneity. Furthermore, in geothermal and petroleum reservoir design, engineers can take advantage of thermal fracturing that occurs when heat transfers between injected flow and the rock matrix to create reservoir permeability. These thermal stresses are calculated using coupled THM analysis and their influence on crack propagation during reservoir stimulation are investigated using damage mechanics and thermal loading algorithms for newly fractured surfaces.