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Cavern leaching at SPR associated with 2017 oil sales and exchanges

Chojnicki, Kirsten

In 2017 small-scale drawdowns at the Strategic Petroleum Reserve (SPR) supported oil sales for the Bipartisan Budget Act of 2015 and the 21st Century Cures Act of 2015 as well as exchanges supporting relief efforts for hurricane Harvey. These drawdowns may affect cavern stability and available drawdowns, thus is important to assess the leaching effects on the cavern shape. Cavern shape estimates from the SANSMIC solution mining code suggest the shapes of 28 caverns were altered in 2017 to varying degrees depending on the total volume of water injected, the initial cavern shape and the distance between the hanging string depth and the oil-brine interface depth. A flaring of the cavern floor occurred in 13 caverns, a geomechanically unfavorable outcome that may require operational changes to preserve cavern integrity. Of the three caverns with post-sale sonars, SANSMIC predictions compared favorably to two but underpredicted the third.

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TYPE SAND Report YEAR 2019
DOIDOIOSTIOSTI

Integral Experiment Request 230 CED-2 Summary Report

Harms, Gary A.; Zerkle, Michael L.; Clarity, Justin B.; Heinrichs, David P.

A method is described to test the effect of increased moderation on the 7uPCX critical arrays using the existing assembly hardware. The proposed experiments will allow the exploration of the assembly fuel-to-water ratio out to, and possibly beyond, optimum moderation in the assembly. A significant result reported below is that the total uncertainty in the benchmark keff in some of these experiments is reduced by about a factor of two compared to the uncertainties obtained in the fully-reflected experiments done to date.

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TYPE Other Report YEAR 2019
OSTIDOIOSTI

SCEMA: A high channel density electronics module for fast waveform capture

Journal of Instrumentation

Brown, J.; Brubaker, Erik M.; Steele, J.; Nishimura, K.

The development of fast, highly pixelated photodetectors with single-photon sensitivity has the potential to enable a variety of new radiation detection concepts. Systems that desire to employ these detectors without loss of information demand waveform digitization with high sampling rates. Switched capacitor arrays provide a low-cost, low-power, compact solution to fast readout with high channel density. The Sandia Laboratories Compact Electronics for Modular Acquisition (SCEMA) was developed to meet these demands. A single module employs two domino ring sampling switched capacitor arrays (DRS4) [1] to provide 16 channels of up to 5 GS/s waveform digitization. This paper presents an overview of the board design and function. Calibration procedures for the module are discussed. Finally, temporal resolution tests are presented demonstrating the module's viability as readout for high fidelity temporal measurements of single photons in suitable photodetectors.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus

Hardware MPI message matching: Insights into MPI matching behavior to inform design: Hardware MPI message matching

Concurrency and Computation. Practice and Experience

Ferreira, Kurt B.; Grant, Ryan; Levenhagen, Michael; Levy, Scott; Groves, Taylor

Here, this paper explores key differences of MPI match lists for several important United States Department of Energy (DOE) applications and proxy applications. This understanding is critical in determining the most promising hardware matching design for any given high-speed network. The results of MPI match list studies for the major open-source MPI implementations, MPICH and Open MPI, are presented, and we modify an MPI simulator, LogGOPSim, to provide match list statistics. These results are discussed in the context of several different potential design approaches to MPI matching–capable hardware. The data illustrate the requirements for different hardware designs in terms of performance and memory capacity. Finally, this paper's contributions are the collection and analysis of data to help inform hardware designers of common MPI requirements and highlight the difficulties in determining these requirements by only examining a single MPI implementation.

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TYPE Journal Article YEAR 2019
DOIDOIOSTIOSTI

Quantum dots with split enhancement gate tunnel barrier control

Applied Physics Letters

Rochette, S.; Rudolph, Martin; Roy, A.M.; Curry, Matthew; Eyck, G.A.T.; Manginell, Ronald; Wendt, Joel R.; Pluym, Tammy; Carr, Stephen M.; Ward, Daniel R.; Lilly, M.P.; Carroll, M.S.

We introduce a silicon metal-oxide-semiconductor quantum dot architecture based on a single polysilicon gate stack. The elementary structure consists of two enhancement gates separated spatially by a gap, one gate forming a reservoir and the other a quantum dot. We demonstrate that, in three devices based on two different versions of this elementary structure, a wide range of tunnel rates is attainable while maintaining single-electron occupation. A characteristic change in the slope of the charge transitions as a function of the reservoir gate voltage, attributed to screening from charges in the reservoir, is observed in all devices and is expected to play a role in the sizable tuning orthogonality of the split enhancement gate structure. The all-silicon process is expected to minimize strain gradients from electrode thermal mismatch, while the single gate layer should avoid issues related to overlayers (e.g., additional dielectric charge noise) and help improve the yield. Finally, reservoir gate control of the tunnel barrier has implications for initialization, manipulation, and readout schemes in multi-quantum dot architectures.

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TYPE Journal Article YEAR 2019
DOIDOIOSTIScopusOSTIScopus

Oil and gas flow through fractures and along interfaces in well cement

Stormont, John C.; Taha, Mahmoud R.; Anwar, Ishtiaque; Hatabeigi, Mahya; Chojnicki, Kirsten N.

A number of wells at the Strategic Petroleum Reserve (SPR) have shown sustained, positive pressure (referred to as sustained casing pressure or SCP) in the cemented annulus behind the production casing. To better understand how SCP may develop for SPR conditions, we conducted gas and oil flow tests on cement specimens with flaws including cement fractures and discrete interfaces along a cement-steel contact. Many specimens were tested initially with gas, followed by oil, and finally with gas again to identify how the fluid type may affect the flow through flaws in the well cement. Nitrogen was used as the gas, and silicone oil with properties similar to typical crude oil was used in most tests. One set of measurements were made with crude oil. Composite steel-cement specimen with corroded steel were also tested. For both gas and oil tests, the measured flow test data were used to interpret permeability and, assuming the cubic law for flow between parallel plates, the corresponding hydraulic aperture of the flaw. The hydraulic apertures for the flawed specimens ranged from about 20 to >100 μm, which corresponds to permeabilities of about 10-14 to 10-12 m2, respectively; these hydraulic apertures are consistent with the range of values interpreted from field measurements on leaky wells. Observed differences between the flow of gas and oil were attributed to a number of factors, including non-linear flow of gas, possible blocking of flow paths by solids within the crude oil, two-phase gas and oil flow and the presence of residual oil in the cement flaw. Furthermore, we determined that corroded steel itself is permeable. Using input values consistent with the gas and oil flow measurements, we conducted one-dimensional simulations of gas and oil flow through cemented annulus systems to investigate the role of flaw size and fluid type on the expected response (i.e., pressure build-up) in the annular cement.

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TYPE SAND Report YEAR 2019
DOIOSTI

Compressed Optimization of Device Architectures for Semiconductor Quantum Devices

Physical Review Applied

Ward, Daniel R.; Frees, Adam; Gamble, John K.; Blume-Kohout, Robin; Eriksson, M.A.; Friesen, Mark; Coppersmith, S.N.

Recent advances in nanotechnology have enabled researchers to manipulate small collections of quantum-mechanical objects with unprecedented accuracy. In semiconductor quantum-dot qubits, this manipulation requires controlling the dot orbital energies, the tunnel couplings, and the electron occupations. These properties all depend on the voltages placed on the metallic electrodes that define the device, the positions of which are fixed once the device is fabricated. While there has been much success with small numbers of dots, as the number of dots grows, it will be increasingly useful to control these systems with as few electrode voltage changes as possible. Here, we introduce a protocol, which we call the "compressed optimization of device architectures" (CODA), in order both to efficiently identify sparse sets of voltage changes that control quantum systems and to introduce a metric that can be used to compare device designs. As an example of the former, we apply this method to simulated devices with up to 100 quantum dots and show that CODA automatically tunes devices more efficiently than other common nonlinear optimizers. To demonstrate the latter, we determine the optimal lateral scale for a triple quantum dot, yielding a simulated device that can be tuned with small voltage changes on a limited number of electrodes.

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TYPE Journal Article YEAR 2019
DOIDOIOSTIOSTI
Results 26601–26800 of 101,000
Results 26601–26800 of 101,000
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