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

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 includes drilling wellbore integrity / lost returns, drill cuttings disposal, and hydraulic fracture water injection.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 solutions for extreme values of rock and fluid properties and leak-off conditions (with all realistic physical problems lying within these extremes). A comprehensive suite of large-scale laboratory experiments were also conducted and models were used to replicate conditions and results of these experiments. Larger finite element models were then constructed and used to demonstrate applicability to a broad range of realistic oil & gas problems, including 2D and 3D problems with large length scales and long time scales 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 agreement with laboratory experiments for a similar range of conditions. The models scale up from lab to well scales and have shown good applicability for a diverse set of realistic and 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 full 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.