Rapidly reducing temperature in cells and MINC problem

Hello,

I'm trying to recreate the simulation of the Coso EGS as published by Kovac et al on the Stanford Geothermal workshop in 2006. I have two questions that I would be grateful to have some replies and thoughts on:

1. The reservoir is of dual porosity and the two rock "types" have different mineralogy. I know how to define the matrix and the fracture with different physical characteristics but cannot get my head around how to define different mineralogies of the two continua.

2. Because of the above problem, I decided to set up the problem in different way just as to be able to run it and have some results to study. Therefore I created a 2 d model with 1 m with, then I have one cell that is 0.1 m (with all the caracteristics of fracture) and the other is 0.9 meters representing the matrix. I introduce a small amount of water into the first fracture cell (0.01 kg/s) of water at 77 C (322 kJ/kg). I then produce on the other end of the column. Finally I apply a little bit of heat to all the matrix cells. However, the temperature of the model decreases rapidly towards zero when I'm injecting. Can anyone please tell me why this could happen?

Thanks