Investigations into the coupled fluid flow and mechanical creep closure behavior of waste disposal rooms in bedded salt

This paper presents the results of numerical simulations of a Waste Isolation Pilot Plant (WIPP) disposal room. In particular the results show: (1) that an initially empty disposal room will consolidate in 195 years to less than 10% of is initial volume, (2) that if waste, backfill, and gas generation are allowed to generate backstress, room consolidation ceases at about 9--10 MPa backstress and room expansion can occur with backstress slightly higher than 9--10 MPa, (3) that reducing the gas generation potentials and rates by a factor of five, drops the maximum room pressure from about 22 MPa to about 18 MPa and decreases the minimum room porosity from about 0.30 to 0.09, (4) that for two-phase fluid flow, brine and gas are driven out of the disposal room into the nonhalite interbeds and that pressures build in these interbeds near the disposal room, and (5) that the interbed pressurization shown in the two-phase flow can exceed lithostatic pressure of 14.8 MPa, which has the potential of opening preexisting fractures between disposal rooms in about 270 years. This work demonstrates the complex interdependent interactions of creep closure affecting void volume, gas pressurization, brine flow, gas generation, and interbed fracture dilation.more » Finally, work aiming at achieving greater coupling in the simulations of WIPP disposal rooms is discussed.« less