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The Born approximation was user) to investigate the influence of a dens>' plasna on the inelastic scatteriig of electrons by one-electron ions. Scaled collision strengths 2 •*> for Is + 2s, Is -• 2p and 2s • 2p transiMons in an ion of arbitrary nuclear charge 2 were computed for a Debye-Huckel model of th

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Hydrates amass beneath and around production equipment and can form in hydrocarbon−seawater jets/plumes. The sources of hydrocarbons in these hydrates are natural seeps or temporary production system leaks. In this paper, some of (i) the formation parameters for these hydrates and (ii) the impacts on normal production operations and hydrocarbon-spill capture systems are discussed. ■ INTRODUCTIONChallenges in the design of deepwater production systems include management of hydrates external and internal to the production hardware. This paper focuses entirely on external hydrates. These include hydrates in which the forming-gas sources are near-mudline natural seeps or production fluid leaks. Management of external hydrates is significantly different from internal-hydrates management for two reasons: (1) The goals of external-hydrates management are often quite different from those of internal-hydrates management. For example, external-hydrates management of near-mudline reservoir hydrates seeks to maintain or increase the volume fractions of these hydrates as they contribute to mudline equipment and wellbore stability. (2) The parameter paths along which external and internal hydrates move into the hydrate region are usually different. For example, at a water depth of 5000 ft in the Gulf of Mexico, (a) in an internal steady-state flowing production line with free gas present, (i) liquids are close to gas saturated, (ii) the pressure and temperature decrease as the fluids flow along the line (in the 40°F seawater environment), which can move the system into the hydrate region (see Figure 1), and (iii) the system is far (>30°F) into the hydrate region at 2200 psi and 40°F (see Figure 1), which promotes relatively fast hydrate-formation kinetics. (b) In an external (to the production system) environment with seeps, (i) seawater is near 40°F in temperature and up to 6000 psi in pressure, (ii) seawater is typically under-saturated with gas, and (iii) elevating the seawater dissolved-gas concentration sufficiently to enter the hydrate region can be difficult in locations with ocean currents. (c) In an external (to the production system) environment with rare, temporary leaks, (i) leak−seawater plume temperature decreases from the leak hydrocarbon temperature (e.g., 200°F) to the seawater temperature (∼40°F ) with the distance up from the source, (ii) seawater is typically under-saturated with gas, and (iii) elevating the seawater dissolved-gas concentration sufficiently to enter the hydrate region can be difficult in locations with ocean currents.In other words, the evolution into the hydrate region for internal systems is usually dominated by a decrease in the Figure 1. Hydrate region boundary plot for a system below the bubble point with flowline fluid pressure−temperature trace. Note that the pressure−temperature point at the flowline outlet is more than 30°F inside the hydrate region, which promotes fast hydrate-formation kinetics.Article pubs.acs.org/EF

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