Learning Outcomes:
By the end of the module students should be able to:
Describe the key properties of fractures and fracture systems using terminology appropriate for different application areas.
Describe the different ways that fractures and fracture properties are represented in subsurface models.
Assess the suitability of different fracture modelling approaches as a function of geological scenario and geo-engineering requirement.
Indicative Module Content:
The module consists of a couple of introductory lectures, a day’s fieldwork, and a three-day student driven modelling exercise. An end-of module exam covers material from all of these components.
Lecture 1: Fractured rocks
What is fractured rock: Fractures and stress regimes; Failure envelope and fracture types; Joint sets, spacing, association with folds, Joint swarms; Stratabound and non-stratabound fractures; Shear fractures (faults); Compactive shear bands and stylolites. Modelling Fractures as baffles and conduits: Caine’s conceptual model of the permeability structure of fault zones; Managing low permeability faults in flow models; Managing high permeability fractures in flow models. What are Naturally Fractured reservoir or aquifers: Type 1, Type2 and Type3 reservoirs; Local and reservoir-scale heterogeneity.
Lecture 2: Fractured rock characterisation and modelling
Primary and secondary fracture characteristics. Characterisation from 1D data. Fracture frequency, intensity and dimensionless intensity: Orientation correction of intensity, Fracture intensity and length distribution, Fracture spacing characterisation. Fracture connectivity: Percolation thresholds and dimensionless intensity, Influence of fracture network topology and clustering. Fracture system modelling for flow: Stratabound and non-stratabound system.
Fieldwork
A day will be spent characterising fractures with the granite outcrops at Bullock Harbour (Dublin).
Discrete fracture reservoir modelling
This student-driven exercise is designed to provide experience in modelling workflow definition and execution. The class will be split into pairs of students who must built a 3D discrete fracture network model based on data collected during the fieldwork, for the purpose of assessing the permeability structure of the fractured granite. The students must assess the capabilities of the recourses available against other possible software and make recommendations for how your study could be improved, given other resources and more time. Three full days will be timetabled for the modelling. Assessment of this component will include both teamwork and individual components and will be based on a presentation summarising the work undertaken, as well as a demonstration of the model.