Abstract

Analysis of fluid flow through 2-D fracture networks using GIS and Matlab

By

Carlos Molina

This study describes a general purpose computer program for analyzing water flow through fractured rock blocks as a two-dimensional simulation model.

This model is based on a discrete network simulation analysis performed by Priest (1993) who used a mathematical approach to predict fluid flow behavior based on the fracture geometry and data on the transmissivity of individual fractures. It works by modeling flow in each fracture and ensuring conservation of fluid mass at fracture intersections (nodes), and a matrix is formed from the equations and then solved to determine the distribution of hydraulic head at all points in the fracture network.

The computer program was written with MATLAB, which is a mathematical computer program designed mainly for dealing with matrices and vectors. The advantage of this program is its easy interaction with the user and the applicability to more than one pattern of fractures. The user is required to scan the image containing the fracture network and to import it into Arcview (a GIS software package). From Arcview the user determines the intersections in the fracture network, which will be considered as nodes later by the MATLAB program. In addition, the program requires information such as hydraulic head of the known boundary nodes in the network, individual fracture apertures, and a .dat file, that can be written in excel, containing a list of unknown internal nodes with their surrounding nodes.

The program will return a list with the hydraulic head for the internal nodes and the total flow into and out of the network in millimeters and any lateral flow if it exists. Finally, the program shows the percentage error during the calculation.