A General Framework for Fracture Intersection Analysis: Algorithms and Practical Applications

Abstract

The modelling and simulation of fracture networks is a critical component of the assessment of hot dry rock (HDR) geothermal resources and of the design and creation of enhanced geothermal systems (EGS). The production of geothermal energy from an EGS depends on fluid pathways through the HDR and thus connectivity of fractures is essential. One way of assessing and modelling fracture connectivity is by intersection analysis. There is a notable lack of research in this area reported in the published literature probably because of the extreme complexity of three-dimensional fractures in HDR especially with respect to their geometrical characteristics i.e., shapes and orientations and spatial interrelationships in the fracture network.

In this paper we present a framework for threedimensional intersection analysis of fracture networks. The framework includes several robust algorithms for three-dimensional geometrical operations on various data structure configurations. We present two case studies to demonstrate the framework.

The first case study is a stochastic fracture network model generated by Monte Carlo sampling of marked point processes that incorporate the most significant fracture characteristics: location, orientation and shape. The second case study is a database of real measurements of fracture parameters. The proposed framework demonstrates the potential to accommodate any amount of complexity e.g., complicated intersections in a fracture network such as varying intensity, varying geometry and numbers of fractures. The resulting fracture intersection databases can be used for further applications such as statistical and spatial analysis of intersections and connectivity analysis.