Characterisation of Natural Fracture Networks by Fluid Flow Modelling: Application of the Parallel Plate Model

Sanderson, D. J., Lonergan, L., Leckenby, R. J.

1 Department of Earth Science & Engineering, Royal School of Mines, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2BP, UK

Robert.Leckenby@ic.ac.uk

By significantly modifying the hydraulic behaviour of otherwise homogeneous porous media, fractures and faults influence many crustal processes such as deformation, mineralisation or fluid migration, both in aquifers and in hydrocarbon reservoirs. A sound understanding of the hydraulic properties of faults and fractures under different stress conditions is therefore fundamental to modelling fluid flow.

The aims of this project are to build realistic 3-Dimensional models of fracture networks at different scales, to produce a catalogue of ‘type’ pressure transient curves for flow through these models using industry software. These curves will be used to refine reservoir characterisation in conjunction with another method presented here.

Using the parallel plate model for flow in fractures, we produced flow heterogeneity maps using examples of natural fracture networks from the Liassic limestones of the north Somerset coast. An example of which is shown in figure 1. We then attempted to correlate flow rates to fracture density in natural fracture systems in order to characterise different structural settings based on their anticipated hydraulic behaviour.

The method used here is easily applicable to any fracture network where aperture measurements have been mapped in detail and allows a fast comparison of fracture flow characteristics in different settings.

It has already been possible to illustrate the heterogeneity of flow in transpressive and extensional examples.

A primary objective of our assessment is to evaluate the applicability of fracture density data as a proxy for permeability in fluid flow modelling. We aim to compare our results with those derived from the parallel plate model.