Advanced Theoretical and Numerical Models of Failure Mechanism and Fracture Propagation Around the Boreholes in Hydro‐Fracturing Process of Hot Dry Rock Reservoirs

Abstract

This paper describes progress on the development of theoretical models required for studying failure mechanism, crack initiation and growth around the boreholes driven by hydrofracturing processes in Hot Dry Rock (HDR) reservoirs of geothermal energy. Due to the importance of the stress intensity factor concept (K) in Fracture Mechanics, some advanced modeling techniques for accurate and fast determination of K for relevant problems are proposed. Alternative tools to deal with stress intensity factor determination are developed and assessed from the points of view of accuracy and computational cost. We concentrate on residual strength, crack initiation and crack growth as a means to model and understand experimentally observed behaviors. Several modeling methods such as compounding and weight function techniques, and boundary and finite element modeling for stress intensity factor calculation are discussed. Further to reviews of those techniques, work performed included (i) developing alternative solutions to deal with boundary‐to‐boundary interaction when using the compounding technique, (ii) relating the precision of K calculations with the level of precision of the crack opening displacement of a reference solution, in order to assess the precision of weight function technique, (iii) modeling relevant geometries using the finite element method (FEM), (iv) working on the implementation of direct stress intensity factor K determination in the Higher Order Displacement Discontinuity Method (HODDM), and (v) developing tools to deal with residual stress fields around the boundary of the hydraulically pressurized boreholes.

Citation

Hossein Kohsary, A., Fatehi Marji, M. and Hosseini Nasab, H. (2007), "Advanced Theoretical and Numerical Models of Failure Mechanism and Fracture Propagation Around the Boreholes in Hydro‐Fracturing Process of Hot Dry Rock Reservoirs", Multidiscipline Modeling in Materials and Structures, Vol. 3 No. 3, pp. 269-286. https://doi.org/10.1163/157361107781389553