Fully-Coupled 3D Hydraulic Fracture Models: Development, Validation, and Application to O&G Problems

Abstract

Abstract This paper describes the development, validation, and application of new 3D finite element models for a diverse set of oil & gas problems involving fluid-driven fractures. Applications described in the paper include borehole integrity and lost returns, drill cuttings re-injection (CRI), and produced water reinjection (PWRI). The models were developed and implemented in a commercially available finite element (FE) software package. The models include both cohesive elements (mesh conforms to pre-defined fracture orientation) and extended finite elements (fracture geometry evolves independent of the finite element mesh). Advantages and disadvantages of each approach will be described. The models were validated through comparisons with published analytical asymptotic solutions for limiting values of rock and fluid properties and leak-off conditions (with practical problems of interest lying within these limits). A comprehensive suite of large-scale laboratory experiments were also conducted and models were used to replicate the conditions and results of these experiments. Larger 2D and 3D finite element models were then constructed and used to demonstrate applicability to a broad range of realistic oil & gas problems, including problems with large length and long time scales. Tractable simulation of these problems was enabled by high-performance, massively parallel computing systems. The models show excellent agreement with published analytical solutions for a broad range of rock and fluid properties and fracturing conditions. The models also show reasonable agreement with laboratory experiments for a similar range of conditions. The models scale up from lab to well scales and have shown practical applicability for a diverse set of challenging oil and gas problems. Most hydraulic fracture models fall into the categories of fast-running but with simplified physics, or complex physics but computationally impractical for full-scale commercial applications. The models described in this paper have been applied at commercial time and length scales, but also provide for full representation of the complex physics of hydraulic fracturing, as demonstrated by the comprehensive validation with analytical solutions and laboratory experiments.