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Active CO2 Reservoir Management: Combining Brine Extraction, Desalination, and Residual-Brine Reinjection with CO2 Storage in Saline Formations

Speaker: Thomas A. Buscheck and Thomas J. Wolery, Lawrence Livermore National Laboratory
Series: EEWR Brown Bag Seminars
Location: Bowen Hall Auditorium
Date/Time: Friday, November 19, 2010, 12:00 p.m. - 1:00 p.m.

Abstract:

In order to stabilize atmospheric CO2 concentrations for climate change mitigation, CO2 capture and storage (CCS) implementation must be increased by several orders of magnitude over the next two decades. For industrial-scale CO2 injection in saline formations, pressure increase is a limiting factor in storage capacity and risk mitigation because it drives CO2 and brine migration. We consider managing both pressure and the migration of CO2 and brine, using Active CO2 Reservoir Management (ACRM), contrasting it with the conventional CCS approach, which we call Passive CO2 Reservoir Management. Combining brine extraction/treatment and residual-brine reinjection with CO2 injection causes “push-pull� manipulation of the CO2 plume, exposing less of the caprock seal to CO2 and more of the storage formation to CO2, with a greater fraction of the storage formation utilized for trapping mechanisms. ACRM reduces pressure buildup, which increases CO2 storage capacity and reduces brine migration. If the net extracted volume of brine is equal to the injected CO2 volume, pressure buildup is minimized, reducing the Area of Review by as much as two orders of magnitude, as well as reducing the risks of induced seismicity, fault activation, and leakage up abandoned wells. The volume of rock over which brine may migrate is reduced by an even greater extent (up to three orders of magnitude), reducing the impact of uncertainty on reservoir analyses of brine migration. Because ACRM allows CO2 and brine migration to be unaffected by neighboring CCS operations, planning, assessing, and conducting each CCS operation within a basin can be carried out independently.

Extracted brine is available as a feedstock for desalination technologies, such as Reverse Osmosis (RO), and, depending on temperature, for geothermal energy production. Geothermal electricity production can defray the cost of CO2 storage, and freshwater production can satisfy the increased water demand from CO2 capture. Geothermal heat recovery is also useful for RO treatment, because the lifetime of RO membranes is greater when brine temperature is 40-50C or less. The feasibility of brine extraction is constrained by brine composition and treatability. Treatment becomes more difficult (and expensive) with increasing total dissolved solids (TDS), ranging from a lower (regulatory) limit of 10,000 mg/L up to about 400,000 mg/L. Specific brine composition does matter, but is less significant. We calculate the result of removing water from brines during RO, focusing on mineral precipitation and increasing osmotic pressure of the residual brine. The rise in the latter is more limiting on practical water extraction. Brines in the TDS range 10,000-40,000 mg/L are prime candidates for RO treatment, using a process used for seawater. Brines in the TDS range 40,000-85,000 mg/L may be treatable by RO alone, but with lower recovery. Above 85,000 mg/L, less conventional methods are necessary, such as NF (nanofiltration) + RO or multi-stage RO. Above 300,000 mg/L, brines are probably untreatable. Data for various western states (e.g., Colorado, Wyoming, and California) show large areas with brine in the 10,000-85,000 mg/L range, indicating ACRM is feasible with respect to brine treatability. The situation is less attractive in other states (e.g., Mississippi and Illinois), where brine salinity is greater.

Brine extraction wells can also function as monitoring wells, providing valuable information about plume movement and hydrogeological heterogeneity, support history matching and model calibration, and later be converted to CO2-injection wells. Altogether, these benefits can reduce the cost of CO2 storage, satisfy the increased water demand from CO2 capture, streamline permitting, and increase public acceptance.

Biography:

Dr. Thomas Buscheckis Group Leader of Geochemical, Hydrological, and Environmental Sciences in the Atmospheric, Earth, and Energy Division at Lawrence Livermore National Laboratory (LLNL). His research involves scientific/engineering model analyses of nonisothermalreactive flow and transport phenomena in fractured porous media, across a range of energy and environmental applications, including underground coal gasification, geologic CO2storage, geothermal energy, and radioactive waste management. He received a Ph.D. in Civil and Geological Engineering from the University of California at Berkeley (UCB) in 1984, an M.S. in Civil Engineering from UCB in 1978, and a B.S. in Civil Engineering from Lafayette College in 1976.

Dr. Thomas Woleryis a geochemist in the Geochemical, Hydrological, and Environmental Sciences in the Atmospheric, Earth, and Energy Division at Lawrence Livermore National Laboratory (LLNL). He is a Principal Investigator on E Program projects, across a range of energy and environmental applications, including geologic CO2storage, geothermal energy, and radioactive waste management. He is the author of the software package EQ3/6, which is widely used at universities and research institutions around the world. He received a Ph.D. in Geological Sciences from Northwestern University in 1978, an M.S. in Geology in 1973 and B.S. in Geochemistry in 1971 from Bowling Green State University.