1. DSSS: Hydraulic Fracturing: Theory – Reality – Uncertainty

    01:40:23

    from LBNL Earth Sciences Division / Added

    188 Plays / / 0 Comments

    ESD welcomes Maurice Dusseault, Ph.D. (Univ. of Waterloo) Hydraulic fracturing (HF) has emerged as an important enabling technique in development of shale oil and shale gas, geothermal energy exploitation, and slurried solids disposal at depth. For example, the City of Los Angeles is injecting biosolids sludge on a trial basis into a depleted reservoir 1350 m deep under HF conditions as a means of treatment, with potential for harvesting generated methane. The challenge facing the geomechanics community is development of a deep understanding and analysis methods for HF in naturally fractured (jointed) rock masses such as igneous rocks, petroliferous carbonates, and shale oil and shale gas reservoirs. Scale is critical: at the tip, local fabric dominates propagation; when fracture length is large, global propagation is dominated by the large-scale principal compressive stresses. Fluid density, viscosity and injection rate affect propagation, and in many cases, induced displacements can change the local principal stress values and lead to secondary fracture arms, an important factor in developing fracture networks. Maurice will discuss what we can and cannot yet do in HF simulation and design. Changes of direction, stress alterations, buoyancy effects, and stress field variations in situ will be discussed. There are no easy answers, the goal of the talk will be to cast some clarity on the physical mechanisms involved in hydraulic fracturing in rock masses with strong fabric, and see what options are available for engineers to pursue in design and implementation of HF technologies.

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    • Constructal Law of Design and Evolution in Nature

      01:27:55

      from LBNL Earth Sciences Division / Added

      170 Plays / / 0 Comments

      www.constructal.org The reoccurring patterns of nature have long puzzled even the most devoted proponents of chance and Darwin’s theory of evolution. But the Constructal Law changes the terms of this debate, and shows that a single law of physics governs the “design” behind everything that moves―whether animate or inanimate. According to the Constructal law, shapes and structures arise because they facilitate movement, in animal design, river basin design, traffic patterns, social dynamics, and technology and sports evolution.

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      • DSSS Enick video

        01:23:45

        from LBNL Earth Sciences Division / Added

        20 Plays / / 0 Comments

        Bob Enick, Ph.D. (University of Pittsburgh). Microorganisms have existed on this planet for more than 3.6 billion years and represent the major drivers for the global biogeochemical cycles. There are about 1030 bacteria in the world, but just 1021 stars in the universe. It is clear that the microbial diversity of the world is a scientific frontier that is not only unexplored, but also of far greater than astronomical dimensions. The microbial ecology of The Arctic is intrinsically fascinating: the low temperatures, extreme seasonality are striking and yet this is a biologically active environment in which nutrients are turned over and pollutants are degraded. The study of the Arctic has gained new urgency as the most rapidly warming region on the planet. The microbial world will mediate much of the anticipated change. There is a ticking “bomb” buried in the Arctic tundra. Enormous quantities of naturally occurring greenhouse gasses are trapped in ice-like structures (clathrates) in the tundra and at the bottom of the seas. The microbial community is central to one of the most disturbing aspects of this warming: the fate of the 400 gigatons of methane locked in the frozen arctic tundra. The microbial community constitutes a lock, currently in a closed position, on these reserves of carbon and the fate of this reservoir. It is correspondingly desirable to understand the nature of this lock, which in turn implies a predictive understanding of the microbial ecology of Arctic soils in our present environment and in a putative and uncertain warmer future.

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        • DSSS: Taking the Fingerprints of Global Sea Level Change

          01:13:22

          from LBNL Earth Sciences Division / Added

          47 Plays / / 0 Comments

          Sea level is a sensitive indicator of climate change, both in the modern world and across geological time. In this regard, all processes that contribute to observed sea-level changes, whether on plate tectonic time scales of millions of years, ice age time scales of thousands of years, or decadal time scales associated with recent global climate change, have distinct geometric signatures. Thus, insight into the underlying processes responsible for sea level change is fundamentally deepened when analyses move beyond simple global averages to consider the detailed geographic variation in geological or geodetic observations. In this talk I will consider examples of this insight from across a broad spectrum of time scales, but I will focus, in particular, on the fingerprints of sea level change in our progressively warming world.

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          • DSSS: Is Brevity the Soul of Soil Models?

            01:08:17

            from LBNL Earth Sciences Division / Added

            37 Plays / / 0 Comments

            ESD welcomes Eric A. Davidson, Ph.D. (Woods Hole Research Center, MA). Soils carbon stocks are 2-4 times greater than atmospheric CO2-C and 3-6 times larger than aboveground plant biomass-C. Potential exists for C sequestration in soils, but there is also a large potential positive feedback to climate change as permafrost thaws and enzymatic decomposition of soil organic matter increases with warming. Enzymatic reaction rates are temperature sensitive when substrate is not limiting. However, substrate supply often, perhaps usually, limits enzymatic reaction rates in soils. Soil microbial community composition varies temporally and spatially, and the reactive properties of extracellular enzymes also can probably be changed by microorganisms in response to environmental cues. The C, N, and P assimilation enabled by extracellular enzyme activity affects the growth of microbial populations, their metabolism, and their enzyme synthesis. Do models need to represent all of these processes in 3-D space and in time? Ideally, the answer would be “yes,” but only if there is a viable approach to testing and validating model structures and parameterizations representing each process. When that is not possible, some aggregation is needed. A modular design enables progress on model components without losing sight of the way that components fit together. Admittedly, the Dual Arrhenius and Michaelis–Menten (DAMM) model does not yet attain all of these lofty goals, but it offers promise to build upon an integrated, modular approach to represent as parsimoniously as possible numerous key interacting processes in a heterogeneous matrix, and to keep making improvements until we get the DAMM thing right.

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            • DSSS: Determining chemical and microbial Fe(II) oxidation kinetics in situ: How well do organisms compete with chemical oxidatio

              01:03:12

              from LBNL Earth Sciences Division / Added

              26 Plays / / 0 Comments

              ESD welcomes George W. Luther, Ph.D. (Univ. of Delaware) The oxidation of aqueous Fe(II) to Fe(III) solids is of great significance to Earth history including banded iron formation (BIFs) and the rise of O2 in waters and the atmosphere. The chemical oxidation of aqueous Fe(II) in air saturated solutions is facile at circumneutral pH, but O2 arises mainly from photosynthetic activity. There are currently three theories on how microbes could have contributed to Fe(III) precipitation: (1) oxygenic photosynthesis, coupled to abiotic Fe oxidation, (2) aerobic (anerobic?) Fe oxidation by iron oxidizing bacteria (FeOB), and (3) anoxygenic photosynthesis, with Fe as an electron donor (photoferrotrophs). Using kinetic data obtained in the field as well as in the laboratory with in situ microelectrode techniques developed in our lab, it is now possible to discriminate between chemical Fe(II) oxidation and these microbially based processes in real time. Field data will be shown from diverse sites including Yellowstone National Park where groundwater, rich in Fe(II) and Mn(II) but with little or no O2, enter oxygenated systems. In the case of FeOB, their importance in Fe(II) oxidation increases at low O2 concentrations. Thermodynamic calculations for the first electron transfer between the metal ions, Fe(II) and Mn(II),with O2 over pH gives insight to the distribution of these metals in BIFs and their biogeochemical behavior.

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              • The vanishing North. How will climate change influence on the microbial genetic resources in Arctic?

                58:02

                from LBNL Earth Sciences Division / Added

                56 Plays / / 0 Comments

                Microorganisms have existed on this planet for more than 3.6 billion years and represent the major drivers for the global biogeochemical cycles. There are about 1030 bacteria in the world, but just 1021 stars in the universe. It is clear that the microbial diversity of the world is a scientific frontier that is not only unexplored, but also of far greater than astronomical dimensions. The microbial ecology of The Arctic is intrinsically fascinating: the low temperatures, extreme seasonality are striking and yet this is a biologically active environment in which nutrients are turned over and pollutants are degraded. The study of the Arctic has gained new urgency as the most rapidly warming region on the planet. The microbial world will mediate much of the anticipated change. There is a ticking “bomb” buried in the Arctic tundra. Enormous quantities of naturally occurring greenhouse gasses are trapped in ice-like structures (clathrates) in the tundra and at the bottom of the seas. The microbial community is central to one of the most disturbing aspects of this warming: the fate of the 400 gigatons of methane locked in the frozen arctic tundra. The microbial community constitutes a lock, currently in a closed position, on these reserves of carbon and the fate of this reservoir. It is correspondingly desirable to understand the nature of this lock, which in turn implies a predictive understanding of the microbial ecology of Arctic soils in our present environment and in a putative and uncertain warmer future.

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