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Open Access Publications from the University of California

Scholarly Works (12 results)

  • Article
LBL Publications (2006)
A common method used to detect leakage from a natural gas storage reservoir includes measuring fluid pressures and watching for pressure increases in the formation above the reservoir. Here we investigate the sensitivity of these pressure measurements for detecting leakage from underground geological formations used for CO2 storage. Calculations are made regarding the rate and extent of pressure buildup associated with different rates of leakage. The number of observation wells needed to detect specified leakage rates are estimated for a range of hydrogeological parameters. In addition, the magnitude of pressure buildup caused by leakage is compared to common forms of "noise" in the pressure data, namely, pressure fluctuations associated with earth tides, barometric pressure variations, precipitation, and instrument resolution and drift. Based on a comparison between the magnitude of the pressure response and the "noise" in the pressure signal, an assessment of the utility of pressure measurements for monitoring leakage from geological storage projects is provided.
    Cover page: Sensitivity of Pressure Measurements for Detecting Leakage of Carbon Dioxide From Geological Storage Sites
    • Article
    LBL Publications (2004)
      Cover page: Determination of moisture diffusivity for unsaturated fractured rock surfaces
      • Article
      • Peer Reviewed
      LBL Publications (2006)

      Sampling of fluids in deep boreholes is challenging because of the necessity to minimize external contamination and maintain sample integrity during recovery. The U-tube sampling methodology was developed to collect large volume, multiphase samples at in situ pressures. As a permanent or semi-permanent installation, the U-tube can be used for rapidly acquiring multiple samples or it may be installed for long-term monitoring applications. The U-tube was first deployed in Liberty County, TX to monitor crosswell CO2 injection as part of the Frio CO2 sequestration experiment. Analysis of gases (dissolved or separate phase) was performed in the field using a quadrupole mass spectrometer, which served as the basis for determining the arrival of the CO2 plume. The presence of oxygen and argon in elevated concentrations, along with reduced methane concentration, indicate sample alteration caused by the introduction of surface fluids during borehole completion. Despite producing the well to eliminate non-native fluids, measurements demonstrate that contamination persists until the immiscible CO2 injection swept formation fluid into the observation wellbore.

        Cover page: Real-time quadrupole mass spectrometer analysis of gas in borehole fluid samples acquired using the U-Tube sampling methodology
        • Article
        • Peer Reviewed
        LBL Publications (2024)
        Correction to: Transport in Porous Media (2024) 151:55–84https://doi.org/10.1007/s11242-023-02033-0. There are three numbers in Table 2 of the original paper that were incorrect. Specfically, the value of the density of hydrogen (H2) for the DB model and the values of density and viscosity of H2 for the TOUGH2 model listed in Table 2 of the original paper were incorrect. (Table presented.) Properties of the H2-water upconing system for comparison against the DB model. Property DB model Used for TOUGH2 Gas cap thickness, total reservoir thickness, and radial extent (outer radius) of the reservoir Infinite, infinite, infinite 50 m, 100 m (with open boundary at bottom), 100 m (open boundary condition) Porosity (ϕ) 0.10 0.10 Permeability (kH) 1.0 × 10−12 m2 1.0 × 10−12 m2 Permeability (kV) 1.0 × 10−12 m2 1.0 × 10−12 m2 Relative permeability (krel) Not applicable Linear with Slr = 0.99 Distance from well to H2-water interface (d) 10 m 10 m Extraction rate of rate of H2 (Qm) − 5.5 kg s−1 − 5.5 kg s−1 Density of water 996 kg m−3 996 kg m−3 Density of H2 7.32 kg m−3 7.87 kg m−3 Viscosity of water 6.54 × 10−4 Pa s 5.11 × 10−4 Pa s Viscosity of H2 9.31 × 10−6 Pa s 9.53 × 10−6 Pa s A corrected Table 2 is shown below. The erroneous values in Table 2 were not used in any of the modeling and simulation. Accurate values for density and viscosity in the modeling and simulation come from CoolProp for the DB model and from EOS7CH for the TOUGH2 simulations.
          Cover page: Correction: Water Upconing in Underground Hydrogen Storage: Sensitivity Analysis to Inform Design of WithdrawalCreative Commons 'BY-ND' version 4.0 license
          • Article
          • Peer Reviewed
          LBL Publications (2023)
          The gas–water interface in Underground Hydrogen Storage (UHS) reservoirs creates the possibility that water will upcone to the well during hydrogen (H2) withdrawal with detrimental impacts. We study the upconing of water to a hydrogen injection/withdrawal (I/W) well using both an analytical solution and numerical simulation. We carried out sensitivity analyses of the engineered properties (e.g., distance of well bottom to gas–water interface, withdrawal rate) and the intrinsic properties (e.g., reservoir permeability, porosity) of an idealized UHS system. Horizontal permeability is the main parameter controlling the height of upconing. Daily I/W cycles to some degree mitigate upconing because injection pushes down the gas–water interface. Sampling-based global sensitivity analyses show clearly that reservoirs with large horizontal permeability are preferred for avoiding upconing. Minimizing withdrawal rate and maximizing either the distance from well to gas–water interface or the length of the perforated well interval are important engineering controls to minimize upconing.
            Cover page: Water Upconing in Underground Hydrogen Storage: Sensitivity Analysis to Inform Design of WithdrawalCreative Commons 'BY' version 4.0 license
            • Article
            LBL Publications (2004)
              Cover page: The Frio Brine Pilot CO2 Sequestration Test - Comparison of Field Data and Predicted Results
              • Article
              LBL Publications (2005)
              Injection of supercritical CO2 into deep, brine-filled reservoirs may be used to slow the effect that greenhouse gas emissions have on global warming. During injection, the large contrast in fluid densities and viscosities causes immiscible displacement of the brine by CO2, resulting in a two-phase system. We performed a series of tracer tests during the Frio CO2 sequestration pilot program to study immiscible and miscible fluid displacement through the Frio sandstone, a deep saline reservoir located beneath the Gulf Coast Region of Texas. A two-well tracer test was initially performed to evaluate miscible fluid displacement in the single-phase, brine-filled reservoir. A dipole flow field was first established by pumping brine from a well penetrating the reservoir and then injecting it back into the same formation using a second well. A tracer, added to the injected water and monitored at the pumping well, allowed us to evaluate interwell travel times and tracer-breakthrough curves. These results are compared to CO2 travel times and gas-tracer-breakthrough curves obtained from immiscible displacement of brine by CO2, collected during a subsequent single-well CO2 flood (radial divergence test). CO2 breakthrough was faster than model predictions, and sweep efficiencies were relatively small, suggesting that gas movement occurred along preferential pathways. Estimates of formation dispersivity, porosity-thickness products and brine saturation provide further insight into the nature of these pathways.
                Cover page: Field Characterization of Reservoir Flow Paths Using Miscible and Immiscible Tracer Tests
                • Article
                LBL Publications (2005)
                  Cover page: The U-Tube: A Novel System for Sampling and Analyzing Multiphase Borehole Fluid Samples during the Frio Brine Pilot Test
                  • Article
                  • Peer Reviewed
                  LBL Publications (2005)

                  A novel system has been deployed to obtain geochemical samples of water and gas, at in situ pressure, during a geologic CO2 sequestration experiment conducted in the Frio brine aquifer in Liberty County, Texas. Project goals required high-frequency recovery of representative and uncontaminated aliquots of a rapidly changing two-phase (supercritical CO2-brine) fluid from 1.5 km depth. The data sets collected, using both the liquid and gas portions of the downhole samples, provide insights into the coupled hydro-geochemical issues affecting CO2 sequestration in brine-filled formations. While the basic premise underlying the U-Tube sampler is not new, the system is unique because careful consideration was given to the processing of the recovered two-phase fluids. In particular, strain gauges mounted beneath the high-pressure surface sample cylinders measured the ratio of recovered brine to supercritical CO2. A quadrupole mass spectrometer provided real-time gas analysis for perfluorocarbon and noble gas tracers that were injected along with the CO2. The U-Tube successfully acquired frequent samples, facilitating accurate delineation of the arrival of the CO2 plume, and on-site analysis revealed rapid changes in geochemical conditions.

                    Cover page: The U-Tube: A Novel System for Acquiring Borehole Fluid Samples from a Deep Geologic CO2 Sequestration Experiment
                    • Article
                    • Peer Reviewed
                    UC Berkeley Previously Published Works (2015)
                    The dissolution of CO2 in water leads to a pH decrease and a carbonate content increase in affected groundwater, which in turn can drive the mobilization of metals from sediments. The mechanisms of metal release postulated in various field and laboratory studies often differ. Drawing primarily on previously published results, we examine contrasting metal mobilization behaviors at two field tests and in one laboratory study, to investigate whether the same mechanisms could explain metal releases in these different experiments. Numerical modeling of the two field tests reveals that fast Ca-driven cation exchange (from calcite dissolution) can explain the release of most major and trace metal cations at both sites, and their parallel concentration trends. The dissolution of other minerals reacting more slowly (superimposed on cation exchange) also contributes to metal release over longer time frames, but can be masked by fast ambient groundwater velocities. Therefore, the magnitude and extent of mobilization depends not only on metal-mineral associations and sediment pH buffering characteristics, but also on groundwater flow rates, thus on the residence time of CO2-impacted groundwater relative to the rates of metal-release reactions. Sequential leaching laboratory tests modeled using the same metal-release concept as postulated from field experiments show that both field and laboratory data can be explained by the same processes. The reversibility of metal release upon CO2 degassing by de-pressurization is also explored using simple geochemical models, and shows that the sequestration of metals by resorption and re-precipitation upon CO2 exsolution is quite plausible and may warrant further attention.
                      Cover page: On the mobilization of metals by CO2 leakage into shallow aquifers: exploring release mechanisms by modeling field and laboratory experiments
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