INTRAVAL phase 2, test case WIPP-I Modeling brine migration in rock salt

Abstract

During the last decade, a very extensive research program has been carried out, by a number of American research organizations, in deep salt formations near Carlsbad, New Mexico, USA. The program is called Waste Isolation Pilot Plant (WIPP). A number of experiments have dealt with the study of movement of brine in the rock salt under the influence of raised temperatures and under formation conditions. A selected set of data from these experiments are included in the international model validation study INTRAVAL. In brine inflow experiments, the rate of seepage of brine into open boreholes is measured as a function of time. In pressure build-up tests, boreholes, with a diameter of 10 cm, are filled with brine and then closed. As a result of flow of brine into the borehole, the brine pressure starts to go up. The pressure in packer-isolated intervals of the borehole is measured as a function of time. Integrated large-scale experiments are carried out in a horizontal cylinderical room, 2.9 m in diamter and 107 m in length. Both pore pressure and brine inflow measurements are carried out in the room and in the surrounding formation. This report presents preliminary results of studying the brine inflow and permeability tests by RIVM group participating in the INTRAVAL study. It is attempted to employ a single model in order to simulate all experiments carried out at the WIPP site. The numerical model METROPOL-2 is employed to simulate the movement of a fluid in a porous medium under a pressure gradient. The general conclusion is that Darcy's law is applicable to the description of brine movement in te rock salt provided that changes in the structure of rock salt, which may cause variation in porosity and permeability are also modeled.