6Periodic hydraulic experiments were conducted in a five-spot well cluster completed in a single 7 bedding plane fracture. Tests were performed by using a winch-operated slug (submerged solid 8 cylinder) to create a periodic head disturbance in one well and observing the phase shift and 9 attenuation of the head response in the remaining wells. Transmissivity (T) and storativity (S) 10 were inverted independently from head response. Inverted T decreased and S increased with 11 oscillation period. Estimated S was more variable among well pairs than T, suggesting S may be 12 a better estimator of hydraulic connectivity among closely spaced wells. These estimates 13 highlighted a zone of poor hydraulic connection that was not identified by a constant rate test 14 conducted in the same wells. Periodic slug tests appear to be a practical and effective technique 15 for establishing local scale spatial variability in hydraulic parameters. 16 1 Introduction 17 Flow channelization has long been recognized as a hallmark of groundwater flow in fractured 18 bedrock systems [Tsang and Neretnieks, 1998]. The physical nature of the problem is described 19 simply through the cubic law which dictates that water flow rate is related cubically to the local 20 fracture aperture. Prediction of flow in a natural bedrock system is not so simple, however, as 21 the distribution of aperture and its interaction with water flow is highly variable even within a 22 single fracture. Understanding flow in bedrock consequently requires site specific hydraulic 23 characterization to be conducted. 24Typical pumping and slug test configurations are not well suited to bedrock environments. 25Because of the small water storage in bedrock, the hydraulic radius of influence of a pumping 26 well extends rapidly outward implying that only the earliest drawdown contains local 27 information. Early drawdown is often dominated by well-bore storage and formation damage 28 effects in open boreholes. Slug test responses are weighted more toward local hydraulics but are 29 even more sensitive to borehole influences. 30 A periodic hydraulic test potentially overcomes some of the limitations of pumping and slug 31 tests. Periodic (also called harmonic, oscillatory, or sinusoidal) tests are conducted by creating 32 an oscillating head in one well and observing the corresponding oscillatory head response in one 33 or more observation wells. Because the head signal is in a constant state of transience, periodic 34 tests highlight the influence of formation storativity on drawdown response. The repeatability of 35 the transience allow initial effects of well bore storage and pump priming to be isolated. Most 36 interestingly, periodic tests are capable of interrogating different portions of the formation 37without the addition of observations wells. This is because the spatial weighting of hydraulic 38 response to transmissivity (T) and storativity (S) is sensitive to the frequency of the head 39 oscillation [Cardiff et al., 2013;Renner and Messar, 2006]. Periodi...

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We present a new method for measuring wettability or contact angle of minerals at reservoir pressure-temperature conditions using high-resolution X-ray computed tomography (HRXCT) and radiography. In this method, a capillary or a narrow slot is constructed from a mineral or a rock sample of interest wherein two fluids are allowed to form an interface that is imaged using X-rays. After some validation measurements at room pressure-temperature conditions, we illustrate this method by measuring the contact angle of CO 2 -brine on quartz, muscovite, shale, borosilicate glass, polytetrafluoroethylene (PTFE or Teflon), and polyether ether ketone (PEEK) surfaces at 60-718C and 13.8-22.8 MPa. At reservoir conditions, PTFE and PEEK surfaces were found to be CO 2 -wet with contact angles of 1408 and 1278, respectively. Quartz and muscovite were found to be water-wet with contact angles of 268 and 588, respectively, under similar conditions. Borosilicate glass-airbrine at room conditions showed strong water-wet characteristics with a contact angle of 98, whereas borosilicate glass-CO 2 -brine at 13.8 MPa and 608C showed a decrease in its water-wetness with contact angle of 548. This method provides a new application for X-ray imaging and an alternative to other methods.

There is a growing need for disposal of high-level nuclear waste. To reduce uncertainty associated with brine availability to repository excavations in salt formations, a collaboration between Sandia, Los Alamos, and Lawrence Berkeley National Laboratories is performing a series of borehole-scale coupled process tests. Here, we report on the first round of the Brine Availability Test in Salt (BATS) project, a "shakedown" experiment called Phase 1s. Experimental testing included placing a resistive heater, a 260-W radiative heater, and a 750-W radiative heater within previously drilled horizontal boreholes at the Waste Isolation Pilot Plant (WIPP) while monitoring temperature and water inflow. The experiments successfully achieved the targeted temperature of 120 • C when using the 750-W radiative heater. Simulations using FEHM (Finite Element Heat and Mass transfer code) and TOUGH-FLAC (Transport Of Unsaturated Groundwater and Heat-Fast Lagrangian Analysis of Continua) were able to accurately predict the coupled thermo-hydro-mechanical-chemical response of salt, matching the observed temperature and brine production. Due to the extremely low permeability of salt, these systems take many years to reach steady state when perturbed by mining activities. Long-term numerical simulations are used to develop the initial pressure and saturation conditions. The inclusion of a damaged rock zone with higher permeability around the borehole also affects the saturation and pressure distributions and plays an important role in dissipating the potential for thermal pressurization. Knowledge gained from this round of experimentation and simulation will be used to conduct the next BATS project experiment in new boreholes at WIPP.

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