HR: 1340h
AN: U43C-1389    [Abstracts]
TI: Formation Dry-out and Salt Precipitation During Injection of CO2 into Saline Aquifers
AU: * Pruess, K
EM: pruess@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, United States
AU: Müller, N
EM: Nadja.Muller@shell.com
AF: Shell International Exploration and Production, Kessler Park 1, Rijswijk, 2288, Netherlands
AB: Injection of CO2 into a saline aquifer may cause formation dry-out and precipitation of salt near the injection well, which may reduce formation porosity, permeability, and injectivity. This paper uses numerical simulation to explore the role of different processes and parameters in the salt precipitation process, and to examine injection strategies that could mitigate the effects. The main physical mechanisms affecting the dry-out and salt precipitation process include (1) displacement of brine away from the injection well by injected CO2, (2) evaporation of brine into the flowing CO2 stream, (3) upflow of CO2 due to gravity effects (buoyancy), (4) backflow of brine towards the injection point due to capillary pressure gradients that oppose the pressure gradient in the CO2-rich ("gas") phase, and (5) molecular diffusion of dissolved salt. The different mechanisms operate on a range of spatial scales. Simulations in 1-D radial geometry are conducted to resolve multi-scale processes by taking advantage of the similarity property, i.e., the evolution of system conditions as a function of radial distance R and time t depends only on the similarity variable R*R/t. Simulations in 2-D vertical cross sections are used to examine the role of gravity effects. We find that counterflow of CO2 and brine can greatly increase aqueous phase salinity, and can promote substantial salt precipitation even in formations with low dissolved solids. Salt precipitation can accentuate effects of gravity override. We also evaluate the efficacy of injecting a slug of fresh water prior to commencement of CO2 injection, as a means of reducing salt precipitation near the injection well. This work was supported by the Zero Emission Research and Technology project (ZERT) under Contract No. DE- AC02-05CH11231 with the U.S. Department of Energy.
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
SC: Union [U]
MN: 2007 Fall Meeting