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Proper control of downhole pressure during cementing operations is critical to maintaining well integrity, i.e. avoiding getting a well kick or fracturing the formation. Contrary to drilling operations where pressure can be monitored in real time thanks to measurement while drilling by downhole tools, no such measurements are available while cementing. Cementing operations must therefore rely on the use of simulations to estimate pressures downhole and ensure that the well integrity is not compromised. These simulations are typically performed ahead of the operations, but for critical wells it is paramount to also perform the calculations in real time to account for any deviation from the plan. We will first provide a description of the hydraulics simulator used for real time simulations. A key feature is the ability to account for fluctuations in injected fluid density, as a result of the cement slurry mixing process. This effectively results in tracking a high number of fluids with different density properties. The simulator also takes into account fluid compressibility and pressure and temperature dependent fluid viscosity, the magnitude of the effects of which we examine in application to generic field cases. Another salient feature of the simulator is its ability to determine whether fluid is lost to the formation by using flow returning from the well as an additional input. We highlight the work accomplished to achieve the performance required for real time computations and then illustrate how the simulator gets used during operation through a case study.

The Cosmic Evolution Survey (COSMOS) was initiated with an extensive allocation (590 orbits in Cycles 12-13) using the Hubble Space Telescope (HST) for high resolution imaging. Here we review the characteristics of the HST imaging with the Advanced Camera for Surveys (ACS) and parallel observations with NICMOS and WFPC2. A square field (1.8$\sq$\deg) has been imaged with single-orbit ACS I-F814W exposures with 50% completeness for sources 0.5\arcsec in diameter at I$_{AB} $ = 26.0 mag. The ACS imaging is a key part of the COSMOS survey, providing very high sensitivity and high resolution (0.09\arcsec FWHM, 0.05\arcsec pixels) imaging and detecting 1.2 million objects to a limiting magnitude of 26.5 (AB). These images yield resolved morphologies for several hundred thousand galaxies. The small HST PSF also provides greatly enhanced sensitivity for weak lensing investigations of the dark matter distribution., Comment: 21 pages, 6 figures -- to appear in COSMOS ApJ Suppl. special issue

We present extensive optical and infrared photometry of the afterglow of gamma-ray burst (GRB) 030329 and its associated supernova (SN) 2003dh over the first two months after detection (2003 March 30-May 29 UT). Optical spectroscopy from a variety of telescopes is shown and, when combined with the photometry, allows an unambiguous separation between the afterglow and supernova contributions. The optical afterglow of the GRB is initially a power-law continuum but shows significant color variations during the first week that are unrelated to the presence of a supernova. The early afterglow light curve also shows deviations from the typical power-law decay. A supernova spectrum is first detectable ~7 days after the burst and dominates the light after ~11 days. The spectral evolution and the light curve are shown to closely resemble those of SN 1998bw, a peculiar Type Ic SN associated with GRB 980425, and the time of the supernova explosion is close to the observed time of the GRB. It is now clear that at least some GRBs arise from core-collapse SNe., Comment: 57 pages, 13 figures, accepted by ApJ, revised per referee's comments, includes full photometry table. Data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB030329 or through WWW at http://cfa-www.harvard.edu/cfa/oir/Research/GRB/