In this study, the potential predictability of the North American (NA) surface air temperature was explored using information-based predictability framework and Ensemble-Based Predictions of Climate Changes and their Impacts (ENSEMBLES) multiple model ensembles. Emphasis was put on the comparison of predictability measured by information-based metrics and by the conventional signal-to-noise ratio (SNR)-based metrics. Furthermore, the potential predictability was optimally decomposed into different modes by maximizing the predictable information (equivalent to the maximum of SNR), from which the most predictable structure was extracted and analyzed.It was found that the conventional SNR-based metrics underestimate the potential predictability, in particular in these areas where the predictable signals are relatively weak. The most predictable components of the NA surface air temperature can be characterized by the interannual variability mode and the long-term trend mode. The former is inherent to tropical Pacific sea surface temperature (SST) forcing such as El Niño-Southern Oscillation (ENSO), whereas the latter is closely associated with the global warming. The amplitude of the two modes has geographical variations in different seasons. On this basis, the possible physical mechanisms responsible for the predictable mode of interannual variability and its potential benefits to the improvement of seasonal climate prediction were discussed.

Abstract-This paper discusses the design, build, and demonstration of two hybrid electric fuel cell utility vehicles for a program sponsored by DLA (Defense Logistics Agency). The design emphasis for the utility vehicles was range extension over state of the art battery systems using a fuel cell power plant. The design work involved vehicle modeling in PSAT to evaluate different battery technologies and compare the effects of different hydrogen storage technologies on vehicle performance and overall range. The comparative analysis showed that 350 bar compressed hydrogen storage maximized vehicle range and produced a final vehicle design that demonstrated a 300+ mile range during commissioning trials.

The shift towards drilling more complex and challenging wells is continuing in the oil & gas industry. Designing such complex wells with narrow error margins requires advanced well planning tools that account for transient phenomena such as the influx of gas during drilling operations. However, most of the available drilling hydraulics software packages currently do not account for advanced well control modeling options when deploying new drilling techniques such as Managed Pressure Drilling (MPD). In this paper, we present a novel multi-phase modeling tool that can be deployed in combination with suitable hydraulic models for MPD well control. Its underlying model preserves the transient multi-phase flow behavior of liquid and gas in the well without overly complicating calculation requirements. It is based on coupled conservation equations of mass, momentum, and energy in association with appropriate closure relationships. Several numerical schemes have been utilized to optimize the accuracy and computational efficiency of the software. Furthermore, a user-friendly graphical user interface has been developed for ease of building the simulation cases. The proposed approach can handle many complexities which occur during a MPD well control incident such as handling multiple influxes from one or several formations, dynamic well control, automated choke control, sudden pump start-up/shut-down, non-Newtonian drilling fluids, arbitrary wellbore path (including directional and horizontal wells), area discontinuity, etc. In addition, this tool can be used to develop and can be used in conjunction with advanced choke control algorithms for MPD. The validity of the software was verified against experimental data from a test well in which a gas kick was induced in a non-Newtonian drilling fluid. The kick was circulated out using the dynamic well control method, which is usually applied during the constant bottom-hole pressure technique of MPD. Parameters such as casing pressure, flow rate in / out of the well, and pit gain were recorded and compared to the simulation results. Excellent agreement was observed between the experimental and simulation results justifying the application of this tool to real-world drilling scenarios. It will be shown that the new tool can accurately estimate parameters such as maximum casing pressure, annular pressure profile, kick tolerance, flow out, pit gain, gas rising velocity, etc. during MPD operations. Applying advanced numerical schemes makes this tool fast, robust, and efficient. As such, it has the potential to improve well control in general and during MPD operations, thereby enhancing rig safety and reducing non-productive time associated with well control-related trouble events.

Non-aqueous drilling fluids (such as synthetic-based mud) are frequently used to drill one or more sections of an oil/gas well to reduce drilling problems such as shale sloughing, wellbore stability, and stuck pipe. However, solubility of formation gas in such fluids makes early gas detection and thereby the well control process very challenging. This is of particular concern in deep offshore wells, in which large amount of gas can be dissolved in non-aqueous drilling fluids under high pressure and temperature conditions. The gas remains in solution until the bubble point is reached. Thereafter, a sudden release of gas at shallow depth can compromise wellbore and riser integrity, particularly when the gas has passed the blow out preventer installed at the seafloor. An advanced planning tool to simulate the transient multi-phase phenomena associated with gas kicks in non-aqueous drilling fluids is therefore highly desirable. This paper presents a novel and comprehensive hydraulic model with associated calculation routines and software to simulate a gas kick in non-aqueous drilling fluids. A transient drift-flux approach based on conservation of mass and momentum was applied in association with appropriate algebraic closure equations and sophisticated friction and choke models. Advanced numerical schemes, where applied previously, have been modified to handle the mass transfer between the liquid (mud) and gas phases. In addition, PVT models have been included to investigate and predict the effect of gas solubility in various types of drilling fluids. The calculation routines contained in a new software tool predict crucial parameters during well construction such as pit gain, gas break out location and void fraction, annular pressure profile, kick tolerance, choke opening, flow-out, standpipe and casing pressures. Simulation results generated using the tool are presented here for both water-based and synthetic-based muds to illustrate the impact of gas solubility on kick behavior. The tool can handle several other complexities which occur during a well control incident such as multiple influxes from one or several formations, dynamic well control (suitable for managed pressure drilling), automated choke control, sudden pump startup/shutdown, non-Newtonian drilling fluids, arbitrary wellbore path, lost circulation, etc. Applying advanced numerical schemes associated with relevant PVT models and several types of boundary conditions makes the tool comprehensive, unique, robust, and efficient for well control analysis for a variety of complex drilling scenarios, particularly deepwater wells. As such, it has the potential to enhance well control operations and well design, thereby enhancing rig safety and reducing non-productive time and cost associated with well control-related events.

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