This article describes the development, validation, and application of a fully coupled Finite Element (FE) framework for modeling of hydraulic fractures in the context of a diverse set of oil & gas (O&G) problems. The models have been developed within a fully-implicit non-linear FE solver, and comprise two widely established fracture modeling methods: Cohesive Zone Method or CZM (mesh conforms to a pre-defined fracture path) and eXtended Finite Element Method or XFEM (fracture geometry evolves independent of the finite element mesh).
The models were verified by comparing simulation results with analytical solutions for the four asymptotic regimes of fracture propagation. The models were also experimentally validated, which involved comparing simulations with carefully conducted polyaxial fracturing experiments. For this purpose, a comprehensive set of laboratory-scale polyaxial fracturing experiments were conducted. Then, the finite element models were used to simulate these experiments, and the simulation results were compared with the experimental results.
The applicability of these models spans conventional as well unconventional fracturing problems, including 3D multi-zone injection, diagnostic fracture injection tests, and multi-stage hydraulic fracturing. To demonstrate this, a number of field-scale models are constructed and applied to a broad range of O&G problems involving fracture propagation at large length and time scales. These include a Step Rate Test (SRT), a Produced Water Re-injection (PWRI) problem, and a Cuttings Re-Injection (CRI) simulation. These large length- and time-scale simulations were enabled by a high-performance, massively parallel computing system.
Through the various validation exercises and the field examples discussed in this work, we intend to demonstrate the applicability of the newly developed fracture modeling capabilities in successfully simulating real problems ranging from laboratory-scale to field-scale.