The LIGO detection of gravitational waves (GW) from merging black holes in 2015 marked the beginning of a new era in observational astronomy. The detection of an electromagnetic signal from a GW source is the critical next step to explore in detail the physics involved. The Antarctic Survey Telescopes (AST3), located at Dome A, Antarctica, is uniquely situated for rapid response time-domain astronomy with its continuous night-time coverage during the austral winter. We report optical observations of the GW source (GW 170817) in the nearby galaxy NGC 4993 using AST3. The data show a rapidly fading transient at around 1 day after the GW trigger, with the i-band magnitude declining from 17.23 ± 0.13 magnitude to 17.72 ± 0.09 magnitude in ∼ 1.8 hour. The brightness and time evolution of the optical transient associated with GW 170817 are broadly consistent with the predictions of models involving merging binary neutron stars. We infer from our data that the merging process ejected about ∼ 10 −2 solar mass of radioactive material at a speed of up to 30% the speed of light.
Phosphonates are widely used scale inhibitors in oilfields for scale control. In this study, crystalline-phase calcium phosphonate nanomaterials were prepared from amorphous silica-templated calcium phosphonate precipitates that were matured into crystalline phases by a simple diafiltration process. The crystalline solids were further dispersed into a surfactant solution to form a nanomaterial suspension (nanofluid) by ultrasonic treatment to expand their use in the delivery of phosphonate inhibitors into formation core materials for scale control. The physical and chemical properties of the synthesized crystalline nanomaterials were characterized by chemical analysis, electron microscopy, X-ray diffraction, infrared microscopy, and thermogravimetric analysis. The transport of the synthesized nanofluids through calcite and sandstone media was investigated using laboratory column breakthrough experiments. The nanofluids were transported through these media at different breakthrough levels. The experimental transport data were correlated using an advection−diffusion equation, as well as colloid filtration theory, with emphasis on the effect of flow velocity on the particle transport. The maximum transport distance of the nanomaterials in porous media was estimated based on the flow velocity and the particle attachment efficiency.
With the advance of new exploration and production technologies, oil and gas production has gone to deeper and tighter formations than ever before. These developments have also brought challenges in scale prediction and inhibition, such as the prevention of scale formation at high temperatures (150-200 C), pressures (1,000-1,500 bar), and total dissolved solids (TDS) (>300,000 mg/L) commonly experienced at these depths. This paper will discuss (1) the challenges of scale prediction at high temperatures, pressures, and TDS; (2) an efficient method to study the nucleation kinetics of scale formation and inhibition at these conditions; and (3) the kinetics of barite-crystal nucleation and precipitation in the presence of various scale inhibitors and the effectiveness of those inhibitors. In this study, nine scale inhibitors have been evaluated at 70-200 C to determine if they can successfully prevent barite precipitation. The results show that only a few inhibitors can effectively inhibit barite formation at 200 C. Although it is commonly believed that phosphonate scale inhibitors may not work for high-temperature inhibition applications, the results from this study suggest that barite-scale inhibition by phosphonate inhibitors was not impaired at 200 C under strictly anoxic condition in NaCl brine. However, phosphonate inhibitors can precipitate with Ca 2þ at high temperatures and, hence, can reduce efficiency. In addition, the relationships of scale inhibition to types of inhibitors and temperature are explored in this study. This paper addresses the limits of the current predition of mineral solubility at high-temperature/high-pressure (HT/HP) conditions and sheds light on inhibitior selection for HT/HP application. The findings from this paper can be used as guidelines for applications in an HT/HP oilfield environment.
A new multi-wavelength solar telescope, Optical and Near-infrared Solar Eruption Tracer (ONSET) of Nanjing University, was constructed, being fabricated by Nanjing Institute of Astronomical Optics & Technology and run in cooperation with Yunnan Astronomical Observatory. ONSET is able to observe the Sun in three wavelength windows: He I 10830Å, Hα, and white-light at 3600Å and 4250Å, which are selected in order to obtain the dynamics in the corona, chromosphere, and the photosphere simultaneously. Full-disk or partial-disk solar images with a field of 10 arcmin at three wavelengths can be obtained nearly simultaneously. It is designed to trace solar eruptions with high spatial and temporal resolutions. This telescope was installed at a new solar observing site near Fuxian Lake in Yunnan Province, southwest China. The site is located at E102N24, with an altitude of 1722 m. The seeing is stable and of high quality. We give a brief description of the scientific objectives and the basic structure of the ONSET. Some preliminary results are also presented.
Scale control in deepwater oil and gas production is often challenging due to not only the geological and mechanical limitation associated with deepwater wells, but also the high temperature (>150°C) and high pressure (>10,000 psi) environment, which may be associated with brine containing high total dissolved solids (TDSs > 300,000 mg/L or greater). These extreme conditions make scale prediction, control and testing difficult because of the requirements for special alloy, pumps and control equipments that are not readily available. Therefore, very few reliable ultra-HTHP data are available. To overcome such challenges, an efficient flow-loop method has been established to study both the equilibrium and kinetics of scale formation and inhibition at ultra-HTHP conditions. This paper will discuss (1) an efficient flow-loop method to study the solubility of scale minerals at ultra-HTHP conditions; (2) solubility of barite at a temperature up to 200°C and pressure up to 20,000 psi; and (3) scale control and inhibitor selection for deepwater oil and gas production at ultra-HTHP conditions. Specifically, the performance and thermal stability of some common scale inhibitors at the high temperature conditions were studied in terms of barite inhibition. The results to-date indicated that (1) the solubility of barite at up to 200°C and 24,000 psi can be precisely measured by this newly developed flow-loop apparatus; (2) the rate of mineral scale formation at HTHP may be considerably faster than previously projected from low temperature studies and hence, difficult to inhibit; (3) different scale inhibitors have shown considerably different thermal stability. The results and findings from these studies validate a new HTHP apparatus for scale and inhibitor testings and information for better scale control at HTHP condition.
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