Ground-water flow modeling of the Culebra dolomite

Abstract

This hydrogeologicmodeling study has been performed aspart of the regional hydrologiccharacterization of the Waste Isolation PilotPiVant(WIPP) sltein southeastern New Mexico.The studyhasproducedan estimation ofthe transmissivity and Darcy-velocity distributions in the CulebraDolomiteMember of the Permian Rustier Formationatthe WIPP site. The results ofthis studyareintendedtosupport SandiaNational Laboratories performance-assessment calculations. The three-dimensional finite-difference codeSWIFT IIwas employedforthe numerical modeling, usinga variable-fluid-density and single-porosity formulation. The spatial scale ofthemodel,21.3km by 30.6km, was chosento allow simulation ofregional-scale pumping tests conductedat t_he H-3 and H-11 hydropadsand theWIPP-13 borehole, which arelocated south,southeast, and northwest, respectively, ofthe centerofthe WIPP site. The modeledareaincludes and extends beyond thecontrolled areadefined by theWIPP-site boundaries.

Phase II Groundwater Flow Model of Corrective Action Unit 98: Frenchman Flat, Nevada Test Site, Nye County, Nevada, Rev. No.: 0

“…The plots of measured hydraulic conductivities versus depth that are reported in the literature tend to show a relatively large amount of scatter, and thus a large amount of spread about any best-fit line, representing the functional relationship of decreasing permeability or hydraulic conductivity versus increasing depth (e.g., Lavenue et al, 1990;DOE/NV, 1997;Belcher et al, 2001 and. However, utilizing these depth-dependent relationships is a useful approach to assist in parameterizing groundwater flow models because often there are limited data available to characterize the full depth and lateral extent of all HSUs in large regional groundwater flow models.…”

Historical Background on Assessment the Performance of the Waste Isolation Pilot Plant

“…Similarly, the 1990 PA used a two-dimensional finite difference code specifically developed for the WIPP, SECOFL2D (Roache, 1993;Rechard, cd., 1992), and divided the Culebra into either 8 or 13 fixed zones. Uncertainty ranges of transmissivity were developed solely from well measurements from each zone in the first case, or well measurements and pilot points of the calibrated fields from the Supplemental EIS (LaVenue et al, 1990;Lappin et al, eds., 1989). In both years, the ranges of transmissivity distributions did not overlap between zonesandthedistributions ofeachzonewere not correlated.…”

“…Sandia convenedanexpertworkinggroup that met in 1991 and 1992 to provide advice on various ways to propagate the uncertainty represented in the transmissivity fields of the Culebra (Zimmerman and Gallegos, 1993). Based on discussion within this group, the original method of Haug et al (1987) and LaVenue et al. (1990) was automated by 1992, which made the procedure feasible for use in a PA. First, multiple transmissivity fields were generated (using TUBA~aVenue and RamaRao, 1992]) and conditioned on transrnissivity data as in 1991 (but using CONSIM [LaVenue and RamaRao, 1992] (LaVenue et al, 1990).…”

Modification and application of TOUGH2 as a variable-density, saturated-flow code and comparison to SWIFT II results

“…Previous studies simulating steady-state flow in the Culebra have been done. One specific study by LaVenue et al (1990) used the SWIFT II code (Reeves et al, 1986), a single-phase flow and transport code, to develop the steady-state flow field. Because gas may also be present in the fluids from the intrusion borehole, a two-phase code such as TOUGH2 can be used to determine the effect that emitted fluids may have on the steady-state Culebra flow field.…”

“…The region of Culebra Dolomite chosen for simulation coincides exactly with the model of LaVenue et al (1990), who used the SWIFT II code (Reeves et al, 1986). The spatial scale of the model, which includes the WIPP-site boundary, is 21.3 km in the east-west direction by 30.6 km in the north-south direction, for a total area of 651.8 km2.…”