Showing papers by "ExxonMobil published in 2009"

Fast full-wavefield seismic inversion using encoded sources

Abstract: Full-wavefield seismic inversion (FWI) estimates a subsurface elastic model by iteratively minimizing the difference between observed and simulated data. This process is extremely computationally intensive, with a cost comparable to at least hundreds of prestack reverse-time depth migrations. When FWI is applied using explicit time-domain or frequency-domain iterative-solver-based methods, the seismic simulations are performed for each seismic-source configuration individually. Therefore, the cost of FWI is proportional to the number of sources. We have found that the cost of FWI for fixed-spread data can be significantly reduced by applying it to data formed by encoding and summing data from individual sources. The encoding step forms a single gather from many input source gathers. This gather represents data that would have been acquired from a spatially distributed set of sources operating simultaneously with different source signatures. The computational cost of FWI using encoded simultaneous-source gathers is reduced by a factor roughly equal to the number of sources. Further, this efficiency is gained without significantly reducing the accuracy of the final inverted model. The efficiency gain depends on subsurface complexity and seismic-acquisition parameters. There is potential for even larger improvements of processing speed.

Modeling elastic properties in carbonate rocks

Abstract: Carbonate (limestone and dolomite) reservoirs account for approximately 50% of oil and gas production worldwide. However, seismic responses in carbonate rocks are poorly understood. In addition, DHI ranking and AVO classification systems developed for clastic rocks are unlikely to be applicable to carbonate rocks. An accurate and physically sound carbonate rock physics model is needed to address these technical issues.

A decision support system for vehicle relocation operations in carsharing systems

Abstract: This paper presents a novel three-phase optimization-trend-simulation (OTS) decision support system for carsharing operators to determine a set of near-optimal manpower and operating parameters for the vehicle relocation problem. Tested on a set of commercially operational data from a carsharing company in Singapore, the simulation results suggest that the manpower and parameters recommended by the OTS system lead to a reduction in staff cost of 50%, a reduction in zero-vehicle-time ranging between 4.6% and 13.0%, a maintenance of the already low full-port-time and a reduction in number of relocations ranging between 37.1% and 41.1%.

Sequence stratigraphy hierarchy and the accommodation succession method

Abstract: We propose a framework for the hierarchy of sedimentary units observed in stratigraphic data that is based entirely on the geometric relationship of the strata. This framework of geometries is assumed to result from repeated successions of accommodation creation and sediment fill (here named accommodation succession). We have modified existing hierarchal frameworks to describe depositional units resulting from accommodation successions of varying magnitude and duration, across a depositional profile. Each full succession consists of component partial succession sets that are, sequentially, lowstand—progradation to aggradational; transgressive—retrogradation; and highstand—aggradation to progradation to degradation. The terms “highstand” and “lowstand” as originally defined to label systems tracts relative to a shelf edge, and with an implied relationship between sea level and systems tracts, have been the root of confusion. We propose that these terms be used in the strict sense of the original definition, because their meaning has been lost when applied to the many depositional settings and high-resolution data sets to which the concepts of sequence stratigraphy are now applied. We propose that the concept of accommodation succession stacking be used in the interpretation of stratigraphic data within a hierarchal framework of depositional sequences, sequence sets, and composite sequences. This will allow an interpreter to accurately categorize observations, provide a basis for predictions away from control points, and develop a framework that allows revisions as higher-resolution data become available.

Morphology-dependent zeolite intergrowth structures leading to distinct internal and outer-surface molecular diffusion barriers.

Abstract: Zeolites play a crucial part in acid–base heterogeneous catalysis. Fundamental insight into their internal architecture is of great importance for understanding their structure–function relationships. Here, we report on a new approach correlating confocal fluorescence microscopy with focused ion beam–electron backscatter diffraction, transmission electron microscopy lamelling and diffraction, atomic force microscopy and X-ray photoelectron spectroscopy to study a wide range of coffin-shaped MFI-type zeolite crystals differing in their morphology and chemical composition. This powerful combination demonstrates a unified view on the morphology-dependent MFI-type intergrowth structures and provides evidence for the presence and nature of internal and outer-surface barriers for molecular diffusion. It has been found that internal-surface barriers originate not only from a 90∘ mismatch in structure and pore alignment but also from small angle differences of 0.5∘–2∘ for particular crystal morphologies. Furthermore, outer-surface barriers seem to be composed of a silicalite outer crust with a thickness varying from 10 to 200 nm. Characterizing the internal architecture of zeolites is crucial for understanding their structure–function relationships, and for acid–base heterogeneous catalysis. Using a unique combination of diffraction and microscopy techniques provides a unified picture of the morphology of intergrowth structures and confirmation of surface barriers for molecular diffusion.

A brief overview of theories of PVC plasticization and methods used to evaluate PVC‐plasticizer interaction

Abstract: This paper reviews the most widely used models for explaining how plasticizers render PVC flexible. These models include the gel, lubricity, and free volume theories; kinetic theories; and mathematical models which predict on the basis of plasticizer structure how much a plasticizer will lower the polymer glass transition in a flexible PVC compound. Since plasticization results from interactions between plasticizer and polymer, methods which have been used to study either the strength or the permanence (or both) of those interactions are also briefly discussed. Tools which have often been used to study plasticizer-PVC interactions include infrared and nuclear magnetic resonance spectroscopy, compression and humid-aging tests, dynamic mechanical analysis, torque rheometer tests, plasticizer-resin clear point temperature measurements, plastisol gelation/fusion by hot stage measurements, and others. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers

Morphodynamic evolution of experimental cohesive deltas

Abstract: [1] Here we describe new techniques for creating river-dominated (birds foot) deltas with strong channelization in the laboratory. The key to achieving strong self-channelization is the addition of a commercially available polymer to the sediment mixture. This polymer enhances the substrate strength increasing the critical erosion stress, an important geomorphic threshold. More importantly it increases the rate of cohesion onset to account for increased rates of morphodynamic evolution in small-scale experiments. A cyclic pattern of delta evolution is observed. The delta “avulsion cycle” begins with channel avulsion, erosion, and channel elongation and ends with channel backfilling and abandonment. This cycle appears to be universal but is subject to a range of controls, including sediment size distribution, sediment concentration, substrate cohesiveness, and Froude number. We propose that the observed depositional cycle is characteristic of an avulsion mechanism that is more complex than current models of fluvial systems, which generally explain avulsion probability as an upstream effect dependent on channel superelevation or levee slope. The experiments suggest that in many distributary channel systems, including deltas, alluvial, and deep water fans, downstream mediated topographic effects or “morphodynamic backwater effects” may dominate over upstream avulsion processes and control the surface mechanics and stratigraphy. The experimental observations are synthesized into a new depositional model for river-dominated deltas which emphasizes the importance of self-organization and feedback in delta surface evolution and stratigraphy.

A dynamic adaptive chemistry scheme for reactive flow computations

Abstract: An on-the-fly kinetic mechanism reduction scheme, referred to as dynamic adaptive chemistry (DAC), has been developed to incorporate detailed chemical kinetics into reactive flow computations with high efficiency and accuracy. The procedure entails reducing a detailed mechanism to locally and instantaneously accurate sub-mechanisms at each hydrodynamic time step of the calculation, and consequently no a priori information regarding simulation conditions is needed. The reduction utilizes an extended version of the directed relation graph (DRG) method in which the edges are weighted by a value that measures the dependence of the tail species (vertex) on the head species. An R-value is then defined at each vertex as the maximum of the products of these weights along all paths to that vertex from an initiating species. Active species are identified by their R-values exceeding a threshold value, eR, using a modified breadth-first search (BFS) that starts from a pre-defined set of initiating species. Chemical kinetics equations are then formulated with respect to the active species, with the inactive species considered only as third body collision partners. The DAC method is implemented into CHEMKIN and tested by simulating homogeneous charge compression ignition (HCCI) combustion using detailed and pre-reduced n-heptane mechanisms (578 species and 178 species, respectively) as the full mechanisms. The DAC scheme reproduces with high accuracy the pressure curves and species mass fractions obtained using the full mechanisms. The on-the-fly mechanism reduction scheme introduces minimal computational overhead and achieves more than 30-fold time reduction in calculations using the 578-species mechanism.

Super‐Resolution Reactivity Mapping of Nanostructured Catalyst Particles

Abstract: For almost a century, heterogeneous catalysts have been at the heart of countless industrial chemical processes, but their operation at the molecular level is generally much less understood than that of homogeneous catalysts or enzymes. The principal reason is that despite the macroscopic dimensions of solid catalyst particles, their activity seems to be governed by compositional heterogeneities and structural features at the nanoscale. Progress in understanding heterogeneous catalysis thus requires that the nanoscale compositional and structural data be linked with local catalytic activity data, recorded in the same small spatial domains and under in situ reaction conditions. Light microscopy is a recent addition to the toolbox for in situ study of solid catalytic materials. It combines high temporal resolution and sensitivity with considerable specificity in distinguishing reaction products from reagents. However, lens-based microscopes are subjected to light diffraction which limits the optical resolution to 250 nm in the image plane. This resolution is far too limited to resolve the nanosized domains on solid catalysts. Nanometer-accurate localization of single emitters can be achieved by fitting a Gaussian distribution function to the intensity of the observed fluorescence spot (point-spread function, PSF). This method has been used to map out diffusion pathways in mesoporous or clay materials under highly dilute conditions. However, for more concentrated systems, several molecules simultaneously located within a diffraction-limited area cannot be distinguished. Separating the emission of the different fluorescent labels in time, for example by selective photoactivation, solves the problem for imaging of static systems, 13–18] but not when looking at the dynamics of a working catalyst. Herein, we used single catalytic conversions of small fluorogenic reactants, which occurred stochastically on the densely packed active sites of the catalyst, to reconstruct diffraction-unlimited reactivity maps of catalyst particles. As successive catalytic reactions do not overlap in time, one can precisely determine the location of reaction sites that show turnovers at different moments in time, even if the distance between them is only 10 nm (or less, depending on the signal-to-noise ratio), and reconstruct images of catalytically active zones with super-resolution. Although fluorogenic substrates are widely used in singlemolecule enzymology, so far only a few studies have reported single-turnover counting using fluorescence microscopy on solid chemocatalysts. 24, 25] Such studies typically use large polycyclic substrates, which cannot enter the micropores of many heterogeneous catalysts. Hence, similar experiments on microporous materials critically depend on identifying a small reagent that is converted to a product detectable at the single-molecule level. Surprisingly, furfuryl alcohol is such a reagent, and it appears that after acid-catalyzed reaction (see the Supporting Information), the pore-entrapped products are sufficiently fluorescent to be individually observed using a standard microscope equipped with a single excitation source (532 nm diode laser) and sensitive CCD camera (for experimental details, see the Supporting Information). We refer to this novel high-resolution reconstruction method based on catalytic conversion of fluorogenic substrates as NASCA microscopy, or nanometer accuracy by stochastic catalytic reactions microscopy. Figure 1a and b show the concept of NASCA microscopy and a 2D fluorescence intensity image of individual product molecules formed by an acid zeolite crystal, respectively. The fluorescence intensity plot of Figure 1c proves how well the intensity of the individual product molecules allows them to be distinguished from background signals, caused by scatter[*] Dr. M. B. J. Roeffaers, Dr. P. Dedecker, Prof. Dr. J. Hofkens Department of Chemistry, Katholieke Universiteit Leuven Celestijnenlaan 200F, 3001 Heverlee (Belgium) Fax: (+ 32)163-2799 E-mail: johan.hofkens@chem.kuleuven.be

Practical methods for measuring the tortuosity of porous materials from binary or gray‐tone tomographic reconstructions

Abstract: Two practical methods are proposed to measure the tortuosity of a porous or permeable material from its tomographic reconstruction. The first method is based on the direct measurement of the shortest distance between two points in the pores, and the second is based on the geodesic reconstruction of the pore or permeation space. Unlike the first method, the second can be directly applied to gray-tone tomograms, without the need of a segmentation step. The methods are illustrated with an electron tomogram of clay/plastic nanocomposite, an X-ray microtomogram of sandstone, and a series of model morphologies consisting of penetrable random spheres. For the latter series, the measured tortuosities compare very well with those derived independently from the theoretical effective diffusion coefficients. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Vertical mantle flow associated with a lithospheric drip beneath the Great Basin

Abstract: Rapid surface uplift or subsidence and voluminous magmatic activity have often been ascribed to regional-scale downwelling of lithospheric mantle. However, because lithospheric drips—sinking plumes of cold and dense lithosphere—are relatively small and transient features, direct evidence of their existence has been difficult to obtain. Moreover, the significant vertical mantle flow that should be associated with such structures has not been detected. Here we integrate seismic anisotropy data with tomographic images to identify and describe a lithospheric drip beneath the Great Basin region of the western United States. The feature is characterized by a localized cylindrical core of cooler material with fast seismic velocities and mantle flow that rapidly shifts from horizontal to vertical. Our numerical experiments suggest that the drip can be generated by gravitational instability resulting from a density anomaly of as little as 1% and a localized temperature increase of 10%. The drip tilts to the northeast—opposite to the motion of the North American plate in the hotspot reference frame—and thereby indicates northeast-directed regional mantle flow. Seismic anisotropy data for the Great Basin region of the western United States, coupled with tomographic images, help delineate a northeast-dipping lithospheric drip. Numerical experiments suggest that the drip could have formed owing to gravitational instability triggered by a density increase of about 1% and a temperature increase of about 10%.

Evidence of Miocene crustal shortening in the North Qilian Shan from Cenozoic stratigraphy of the western Hexi Corridor, Gansu Province, China

Abstract: New sedimentologic, stratigraphie, and compositional data from the Paleogene-Neogene stratigraphie succession exposed in the northwest Hexi Corridor and within the North Qilian Shan, provide evidence to suggest that crustal shortening in the North Qilian Shan fold-thrust belt initiated during die Miocene. The section is composed of four lithostratigraphic units: Oligocene-Miocene fine- to coarse-grained Unit 1, Miocene conglomeratic Unit 2, and Pliocene-Pleistocene conglomeratic Units 3 and 4. Unit 3 lies in angular unconformity over both Units 1 and 2, and Unit 4 contains a progressive unconformity. The onset of conglomerate deposition at the base of Unit 2 suggests an increase in depositional energy, which we interpret as me result of proximal orogenesis in the North Qilian Shan fold and tiirust belt. Supporting evidence includes the appearance of strongly northeast-trending paleocurrents, indicat-ing paleoflow away from the Qilian Shan, clast lidiologies that match sources in the North Qilian Shan, and sandstone with detrital framework modes that indicate a recycled orogen source. In contrast, Unit 1 contains paleocurrent indicators that are variable but generally trend northward and sandstone and clast compositions which are more diagnostic of a continental block source. Detrital zircon age determinations from Unit 1 are also not consistent with a source in the North Qilian Shan; rather, they suggest a provenance in hinterland regions within the South Qilian Shan and North Qaidam terranes. In sum, these results are all consistent with initiation of proximal uplift of the North Qilian Shan during deposition of the gradational transition from Unit 1 to Unit 2, demonstrating shortening in the Qilian Shan before die late Miocene. This comprehensive study tightens our understanding of when far-field stress related to the India-Eurasia continent-continent collision reached the northeastern edge of the Tibetan Plateau.

Low emission power generation and hydrocarbon recovery systems and methods

Abstract: Methods and systems for low emission power generation in hydrocarbon recovery processes are provided. One system includes integrated pressure maintenance and miscible flood systems with low emission power generation. An alternative system provides for low emission power generation, carbon sequestration, enhanced oil recovery (EOR), or carbon dioxide sales using a hot gas expander and external combustor. Another alternative system provides for low emission power generation using a gas power turbine to compress air in the inlet compressor and generate power using hot carbon dioxide laden gas in the expander. Other efficiencies may be gained by incorporating heat cross-exchange, a desalination plant, co-generation, and other features.

Seismic Wave Attenuation in Carbonates

Abstract: [1] The effect of pore fluids on seismic wave attenuation in carbonate rocks is important for interpreting remote sensing observations of carbonate reservoirs undergoing enhanced oil recovery. Here we measure the elastic moduli and attenuation in the laboratory for five carbonate samples with 20% to 30% porosity and permeability between 0.03 and 58.1 mdarcy. Contrary to most observations in sandstones, bulk compressibility losses dominate over shear wave losses for dry samples and samples fully saturated with either liquid butane or brine. This observation holds for four out of five samples at seismic (10–1000 Hz) and ultrasonic frequencies (0.8 MHz) and reservoir pressures. Attenuation modeled from the modulus data using Cole-Cole relations agrees in that the bulk losses are greater than the shear losses. On average, attenuation increases by 250% when brine substitutes a light hydrocarbon in these carbonate rocks. For some of our samples, attenuation is frequency-dependent, but in the typical exploration frequency range (10–100 Hz), attenuation is practically constant for the measured samples.

Elastic wave speeds and moduli in polycrystalline ice Ih, sI methane hydrate, and sII methane-ethane hydrate

Abstract: [1] We used ultrasonic pulse transmission to measure compressional, P, and shear, S, wave speeds in laboratory-formed polycrystalline ice Ih, sI methane hydrate, and sII methane-ethane hydrate. From the wave speed's linear dependence on temperature and pressure and from the sample's calculated density, we derived expressions for bulk, shear, and compressional wave moduli and Poisson's ratio from −20 to −5°C and 22.4 to 32.8 MPa for ice Ih, −20 to 15°C and 30.5 to 97.7 MPa for sI methane hydrate, and −20 to 10°C and 30.5 to 91.6 MPa for sII methane-ethane hydrate. All three materials had comparable P and S wave speeds and decreasing shear wave speeds with increasing applied pressure. Each material also showed evidence of rapid intergranular bonding, with a corresponding increase in wave speed, in response to pauses in sample deformation. There were also key differences. Resistance to uniaxial compaction, indicated by the pressure required to compact initially porous samples, was significantly lower for ice Ih than for either hydrate. The ice Ih shear modulus decreased with increasing pressure, in contrast to the increase measured in both hydrates.

Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

Abstract: [1] Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen availability influences terrestrial carbon sinks and sources in response to changes over the 20th century in global environmental factors including atmospheric CO2 concentration, nitrogen inputs, temperature, precipitation and land use. The two versions of ISAM vary in their treatment of nitrogen availability: ISAM-NC has a terrestrial carbon cycle model coupled to a fully dynamic nitrogen cycle while ISAM-C has an identical carbon cycle model but nitrogen availability is always in sufficient supply. Overall, the two versions of the model estimate approximately the same amount of global mean carbon uptake over the 20th century. However, comparisons of results of ISAM-NC relative to ISAM-C reveal that nitrogen dynamics: (1) reduced the 1990s carbon sink associated with increasing atmospheric CO2 by 0.53 PgC yr 1 (1 Pg = 10 15 g), (2) reduced the 1990s carbon source associated with changes in temperature and precipitation of 0.34 PgC yr 1 in the 1990s, (3) an enhanced sink associated with nitrogen inputs by 0.26 PgC yr 1 , and (4) enhanced the 1990s carbon source associated with changes in land use by 0.08 PgC yr 1 in the 1990s. These effects of nitrogen limitation influenced the spatial distribution of the estimated exchange of CO2 with greater sink activity in high latitudes associated with climate effects and a smaller sink of CO2 in the southeastern United States caused by N limitation associated with both CO2 fertilization and forest regrowth. These results indicate that the dynamics of nitrogen availability are important to consider in assessing the spatial distribution and temporal dynamics of terrestrial carbon sources and sinks.

Experiments on Wedge-Shaped Deep Sea Sedimentary Deposits in Minibasins and/or on Channel Levees Emplaced by Turbidity Currents. Part II. Morphodynamic Evolution of the Wedge and of the Associated Bedforms

Abstract: Rapidly decelerating sediment-laden flows typically emplace confined sedimentary deposits. In the fluvial environment, when sediment-laden rivers reach lakes the decelerating flow emplaces a subaerial delta with distinctive topset, foreset, and bottomset deposits. In the submarine environment, turbidity currents undergoing rapid deceleration commonly emplace sedimentary wedges (i.e., deposits thinning in the downstream direction). Froude-supercritical turbidity currents have an intrinsic self-regulating mechanism for deceleration, in that the faster they flow, the more they incorporate ambient sea water through mixing at their interface. In addition, special topographic configurations, such as the entrance into a zone of much lower slope and/or lateral confinement, or the passage into a confined minibasin, may trigger sudden flow deceleration by forcing a transition to subcritical flow through an internal hydraulic jump. The present paper and its companion present experiments on a generic configuration aimed at studying the emplacement of wedge-shaped sedimentary deposits by continuous supercritical density currents. The deceleration is achieved both by natural entrainment of ambient water and by the presence of an obstructing barrier downstream. Lightweight plastic sediment was used as an analog for sand, and was transported mostly as bedload, but with some suspension, by a saline underflow. The saline underflow served as a surrogate for a turbidity current driven by fine mud that does not easily settle out. The companion paper is focused on the flow patterns associated with the decelerating current. The present paper focuses on the depositional sequences. The decelerating supercritical flows produced a wedge with a distinct pattern of aggradation and progradation. In addition, a foreset-like structure is attributed to the presence of an internal hydraulic jump forced by the downstream barrier. Although they do not reproduce any specific field-scale setting, the experiments are deemed a good generic model for several wedge-shaped submarine deposits in various settings, from slope aprons to deposits in minibasins or on the external flanks of channel levees. The paper also documents the regimes of bedforms associated with the diverse flow regions. It provides the first evidence for the formation of trains of the upstream-migrating sediment waves known as cyclic steps, similar to those commonly observed on channel levees and also along the thalwegs of some steep canyons. In addition, the experiments provide convincing evidence for the formation of downstream-migrating antidunes as well.

Predicting delta avulsions: Implications for coastal wetland restoration

Abstract: River deltas create new wetlands through a continuous cycle of delta lobe extension, avulsion, and abandonment, but the mechanics and timing of this cycle are poorly understood. Here we use physical experiments to quantitatively define one type of cycle for river-dominated deltas. The cycle begins as a distributary channel and its river mouth bar prograde basinward. Eventually the mouth bar reaches a critical size and stops prograding. The stagnated mouth bar triggers a wave of bed aggradation that moves upstream and increases overbank flows and bed shear stresses on the levees. An avulsion occurs as a time-dependent failure of the levee, where the largest average bed shear stress has been applied for the longest time (R 2 = 0.93). These results provide a guide for predicting the growth of intradelta lobes, which can be used to engineer the creation of new wetlands within the delta channel network and improve stratigraphic models of deltas.

Coated oil and gas well production devices

Abstract: Provided are coated oil and gas well production devices and methods of making and using such coated devices. In one form, the coated device includes one or more cylindrical bodies, hardbanding on at least a portion of the exposed outer surface, exposed inner surface, or a combination of both exposed outer or inner surface of the one or more cylindrical bodies, and a coating on at least a portion of the inner surface, the outer surface, or a combination thereof of the one or more cylindrical bodies. The coating includes one or more ultra-low friction layers, and one or more buttering layers interposed between the hardbanding and the ultra-low friction coating. The coated oil and gas well production devices may provide for reduced friction, wear, erosion, corrosion, and deposits for well construction, completion and production of oil and gas.

Finite-difference frequency-domain modeling of viscoacoustic wave propagation in 2D tilted transversely isotropic (TTI) media

Abstract: A 2D finite-difference, frequency-domain method was developed for modeling viscoacoustic seismic waves in transversely isotropic media with a tilted symmetry axis. The medium is parameterized by the P-wave velocity on the symmetry axis, the density, the attenuation factor, Thomsen’s anisotropic parameters δ and ϵ , and the tilt angle. The finite-difference discretization relies on a parsimonious mixed-grid approach that designs accurate yet spatially compact stencils. The system of linear equations resulting from discretizing the time-harmonic wave equation is solved with a parallel direct solver that computes monochromatic wavefields efficiently for many sources. Dispersion analysis shows that four grid points per P-wavelength provide sufficiently accurate solutions in homogeneous media. The absorbing boundary conditions are perfectly matched layers (PMLs). The kinematic and dynamic accuracy of the method wasassessed with several synthetic examples which illustrate the propagation of S-waves excited at t...

Sequence stratigraphy of experimental strata under known conditions of differential subsidence and variable base level

Abstract: Sequence stratigraphy has been applied from reservoir to continental scales, providing a scale-independent model for predicting the spatial arrangement of depositional elements. We examine experimental strata deposited in the Experimental EarthScape facility at St. Anthony Falls Laboratory, focusing on stratigraphic surfaces defined by discordant contact geometries, surfaces analogous to those delineated in the original work on seismic sequence stratigraphy. In this controlled setting, we directly evaluate critical sequence-stratigraphic issues, such as stratigraphic horizon development and time significance, as well as the internal geometry and migration of the bounded strata against the known boundary conditions and depositional history. Four key stratigraphic disconformities defined by marine downlap, marine onlap, fluvial erosion, and fluvial onlap are mapped and vary greatly in their relative degree of time transgression. Marine onlap and downlap contacts closely parallel topographic surfaces (time surfaces) and, prior to burial, approximate the instantaneous offshore topography. These stratal-bounding surfaces are also robust stratigraphic signals of relative base-level fall and rise, respectively. Marine onlap surfaces are of special interest. They tend to be the best preserved discordance, where widespread, allogenic-based onlap surfaces subdivide otherwise amalgamated depositional cycles amidst cryptic stacks of marine foresets; however, local, autogenic-based marine onlap discordances are present throughout the fill. A critical distinguishing feature of allogenic onlap is the greater lateral persistence of the discordance. Surfaces defined by subaerial erosional truncation and fluvial onlap do not have geomorphic equivalence because channel processes continually modify the surface as the stratigraphic horizons are forming. Hence, they are strongly time transgressive. Last, the stacking arrangement of the preserved bounded strata is found to be a good time-averaged representation of the mass-balance history.

Seascape Evolution on Clastic Continental Shelves and Slopes

Abstract: The morphology of clastic continental margins directly reflects their formative processes. These include interactions between plate movements and isostasy, which establish the characteristic stairstep shape of margins. Other factors are thermal and loading-induced subsidence, compaction and faulting/folding, which create and/or destroy accommodation space for sediment supplied by rivers and glaciers. These processes are primary controls on margin size and shape. Rivers and glaciers can also directly sculpt the margin surface when it is subaerially exposed by sea-level lowstands. Otherwise, they deposit their sediment load at or near the shoreline. Whether this deposition builds a delta depends on sea level and the energy of the ocean waves and currents. Delta formation will be prevented when sea level is rising faster than sediment supply can build the shoreline. Vigorous wave and current activity can slow or even arrest subaerial delta development by moving sediments seaward to form a subaqueous delta. This sediment movement is accomplished in part by wave-supported sediment gravity flows. Over the continental slope, turbidity currents are driven by gravity and, in combination with slides, cut submarine canyons and gullies. However, turbidity currents also deposit sediment across the continental slope. The average angle of continental slopes (~4°) lies near the threshold angle above which turbidity currents will erode the seafloor and below which they will deposit their sediment load. Therefore, turbidity currents may help regulate the dip of the continental slope. Internal waves exert a maximum shear on the continental-slope surface at about the same angle, and may be another controlling factor.

Ultra-low friction coatings for drill stem assemblies

Abstract: Provided are drill stem assemblies with ultra-low friction coatings for subterraneous drilling operations. In one form, the coated drill stem assemblies for subterraneous rotary drilling operations include a body assembly with an exposed outer surface including a drill string coupled to a bottom hole assembly or a coiled tubing coupled to a bottom hole assembly and an ultra-low friction coating on at least a portion of the exposed outer surface of the body assembly, wherein the coefficient of friction of the ultra-low friction coating is less than or equal to 0.15. The coated drill stem assemblies disclosed herein provide for reduced friction, vibration (stick-slip and torsional), abrasion and wear during straight hole or directional drilling to allow for improved rates of penetration and enable ultra-extended reach drilling with existing top drives.

Evaluation of Bioaccumulation Using In Vivo Laboratory and Field Studies

Abstract: A primary consideration in the evaluation of chemicals is the potential for substances to be absorbed and retained in an organism's tissues (i.e., bioaccumulated) at concentrations sufficient to pose health concerns. Substances that exhibit properties that enable biomagnification in the food chain (i.e., amplification of tissue concentrations at successive trophic levels) are of particular concern due to the elevated long-term exposures these substances pose to higher trophic organisms, including humans. Historically, biomarkers of in vivo chemical exposure (e.g., eggshell thinning, bill deformities) retrospectively led to the identification of such compounds, which were later categorized as persistent organic pollutants. Today, multiple bioaccumulation metrics are available to quantitatively assess the bioaccumulation potential of new and existing chemicals and identify substances that, upon or before environmental release, may be characterized as persistent organic pollutants. This paper reviews the various in vivo measurement approaches that can be used to assess the bioaccumulation of chemicals in aquatic or terrestrial species using laboratory-exposed, field-deployed, or collected organisms. Important issues associated with laboratory measurements of bioaccumulation include appropriate test species selection, test chemical dosing methods, exposure duration, and chemical and statistical analyses. Measuring bioaccumulation at a particular field site requires consideration of which test species to use and whether to examine natural populations or to use field-deployed populations. Both laboratory and field methods also require reliable determination of chemical concentrations in exposure media of interest (i.e., water, sediment, food or prey, etc.), accumulated body residues, or both. The advantages and disadvantages of various laboratory and field bioaccumulation metrics for assessing biomagnification potential in aquatic or terrestrial food chains are discussed. Guidance is provided on how to consider the uncertainty in these metrics and develop a weight-of-evidence evaluation that supports technically sound and consistent persistent organic pollutant and persistent, bioaccumulative, and toxic chemical identification. Based on the bioaccumulation information shared in 8 draft risk profiles submitted for review under the United Nations Stockholm Convention, recommendations are given for the information that is most critical to aid transparency and consistency in decision making.

Hydrocarbon detection with passive seismic data

Abstract: Method for using seismic data from earthquakes to address the low frequency lacuna problem in traditional hydrocarbon exploration methods. Seismometers with frequency response down to about 1 Hz are placed over a target subsurface region in an array with spacing suitable for hydrocarbon exploration (21). Data are collected over a long (weeks or months) time period (22). Segments of the data (44) are identified with known events from earthquake catalogs (43). Those data segments are analyzed using techniques such as traveltime delay measurements (307) or receiver function calculations (46) and then are combined with one or more other types of geophysical data acquired from the target region, using joint inversion (308-310) in some embodiments of the method, to infer physical features of the subsurface indicative of hydrocarbon potential or lack thereof (26).