Water Challenges for Geologic Carbon Capture and Sequestration

Carbon capture and sequestration (CCS) has been proposed as a means to dramatically reduce greenhouse gas emissions with the continued use of fossil fuels. For geologic sequestration, the carbon dioxide is captured from large point sources (e.g., power plants or other industrial sources), transported to the injection site and injected into deep geological formations for storage. This will produce new water challenges, such as the amount of water used in energy resource development and utilization and the “capture penalty” for water use. At depth, brine displacement within formations, storage reservoir pressure increases resulting from injection, and leakage are potential concerns. Potential impacts range from increasing water demand for capture to contamination of groundwater through leakage or brine displacement. Understanding these potential impacts and the conditions under which they arise informs the design and implementation of appropriate monitoring and controls, important both for assurance of environmental safety and for accounting purposes. Potential benefits also exist, such as co-production and treatment of water to both offset reservoir pressure increase and to provide local water for beneficial use

Physical properties and velocity measurement comparison for sediments from DSDP Holes 92-597B and 92-597C

The bulk and grain densities, porosity, water content, and ultrasonic compressional- and shear-wave velocities of 25 basalt samples from DSDP Holes 597B and 597C were measured. The velocities were measured at in situ pore and confining pressures. The bulk densities of the samples vary between 2.690 and 3.050 g/cm**3. Porosities of selected samples vary between 2.4 and 9.3%. The grain densities vary between 2.993 and 3.117 g/cm3, a range that suggests that bulk density differences are due primarily to variations in porosity. Compressional-wave velocities range from 5.70 to 6.81 km/s, and shear-wave velocities range from 1.66 to 3.84 km/s. The variation in compressional velocity appears to be due primarily to variations in grain size and the associated greater density of grain-boundary cracks for samples with a smaller average grain size. On the basis of these results we would expect compressional and shear velocities to increase with increasing depth in the shallow crust, primarily as the result of the effects of confining pressure on crack density

Permeability Versus Depth in the Upper Oceanic Crust\u27 In Situ Measurements in DSDP Hole 504B, Eastern Equatorial Pacific

In situ permeabilities measured within the upper kilometer of oceanic crust in hole 504B on the south flank of the Costa Rica Rift decrease exponentially from 10-13 to 10-14 m2 in layer 2A (the upper 150m) to 10 -15 to 10-17 m2 in layer 2B (150-550 m into basement), and to 10-17 m2 and lower in layer 2C (deeper than 550 m). We estimate the permeability (k) versus depth (z) to vary as k(z)=0.11e(-z/50)x 10-12 m2. If this permeability versus depth function is representative of the oceanic crust in general, then hydrothermal convection would be vertically stratified, with the most vigorous circulation confined to the shallowest pillow basalt layers of the crust. The use of a full suite of geophysical logs (including borehole televiewer imagery; multichannel, full waveform sonic; nuclear; and variable spacing electrical resistivity logs) allows the characterization of the scale and interconnectedness of fractures, and the degree of infilling of these fractures by alteration minerals. At hole 504B, we observe a relationship between permeability and fracture porosity, determined from the geophysical logs. If fractures with similar aspect ratios are encountered at other oceanic sites, then prediction of the permeability of the oceanic crust to within an order of magnitude is possible from geophysical logs. At hole 395A in the Atlantic, for example, in situ permeability measurements yielded values similar to those predicted by the logging relationships established at hole 504B

UCRL-JC-135091 PREPRINT Electrical Resistance Tomography Using Steel Cased Boreholes as Long Electrodes Electrical resistance tomography using steel cased boreholes as long electrodes

Abstract Electrical resistance tomography (ERT) using multiple electrodes installed in boreholes has been shown to be useful for both site characterization and process monitoring. In some cases, however, installing multiple downhole electrodes is too costly (e.g., deep targets) or risky (e.g., contaminated sites). For these cases we have examined the possibility of using the steel casings of existing boreholes as electrodes. Several possibilities can be considered. The first case we investigated uses an array of steel casings as electrodes. This results in very few data and thus requires additional constraints to limit the domain of possible inverse solutions. Simulations indicate that the spatial resolution and sensitivity are understandably low but it is possible to coarsely map the lateral extent of subsurface processes such as steam floods. The second case uses an array of traditional point borehole electrodes combined with long-conductor electrodes (steel casings). Although this arrangement provides more data, in many cases it results in poor reconstructions of test targets. Results indicate that this method may hold promise for low resolution imaging where steel casings can be used as electrodes but the merits depend strongly on details of each application. Field tests using these configurations are currently being conducted