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Cubic equations of state (EOS) have proven their utility to the petroleum engineers for many decades. Their predictive power remains, however, limited. Statistical mechanical approaches have meanwhile grown allowing the development of powerful engineering equations of state. In particular, this paper investigates how equations that are based on the association term of Wertheim can improve significantly the predictive power in petroleum applications. Three distinct issues are discussed. Mixtures of associating components such as water or methanol with hydrocarbons have so far represented one of the main challenges for the predictive power of equations of state. It is shown that the CPA equation, that combines the classical SRK EOS with the association term of Wertheim, provides a significant improvement for both methanol-hydrocarbon and water-hydrocarbon mixtures. The physical significance of the SAFT parameters makes it possible to develop a group contributions method for their determination. Using this approach, it becomes possible to predict vapour pressure and liquid volume of heavy molecules. This is shown for a number of families, such as n-alkanes, n-alcohols, 1-olefins as well as for isomers of methyl-alkanes. Finally, the improved predictions resulting from the use of polar terms with SAFT are illustrated. The effect of the quadrupole is clearly shown with an aromatic-non aromatic mixture. Including a dipolar interaction makes it possible to differentiate the behaviour of the cis and the trans 2-butene isomers.

In previous works, it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water Nigeria. It was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics. New results obtained by drilling into gas hydrate‐bearing sediments with the MeBo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indicate that pockmark formation and evolution in the study area are mainly controlled by rapid hydrate growth opposed to slow hydrate dissolution. On one hand, positive temperature anomalies, free gas trapped in shallow microfractures near the seafloor and coexistence of free gas and gas hydrate indicate rapid hydrate growth. On the other hand, slow hydrate dissolution is evident by low methane concentrations and almost constant sulfate values 2 m above the Gas Hydrate Occurrence Zone. Free gas trapped in shallow micro‐fractures near the seafloorVery low methane concentrations above the top of the gas hydrate occurrence zonePockmark formation controlled by rapid hydrate growth and hydrate dissolution

The objective of this work is to evaluate whether hydrogen sulfide can be considered an associating compound in the cubic-plus-association (CPA) equation of state (EOS). This EOS is applied in order to calculate its pure substance properties (vapor pressure and saturated liquid volume) and fluid phase equilibrium with hydrocarbons. The investigation was undertaken considering two kinds of association schemes (3B and 4C). The comparison of the CPA results with data taken from the literature gives a good agreement in almost every case. It was observed that the CPA EOS gives reasonable estimates of the vapor−liquid equilibria of hydrocarbon−H2S mixtures (i.e., without binary interaction parameter), while the Soave−Redlich−Kwong EOS needs a binary interaction parameter. Different combining rules for the association energy and association volume parameters have been tested to predict mixtures containing two associating compounds such as H2S−methanol and H2S−water. The 3B association scheme with the “CR-4” mixing rules is finally selected.

A new experimental apparatus has been developed to measure vapor− liquid equilibria (VLE) and vapor−liquid−liquid equilibria (VLLE) for multicomponent systems containing light hydrocarbons, carbon dioxide, methanol, and water at low temperatures. These systems are particularly difficult to investigate experimentally because of the polarity contrast existing between the polar and nonpolar components. In such systems, the phase equilibrium leads to a heterogeneous distribution of the different components into the different phases. Nevertheless, such systems are frequently met in refining processes and in gas treatment. Consequently, it is very important to investigate them experimentally in order to improve the engineering processes. In the present study, we describe a new apparatus which allows to investigate fluid phase equilibrium at low temperature. The experimental setup is presented in detail and the experimental procedures to reach and measure vapor−liquid and vapor−liquid−liquid equilibrium are explained. This equipment has been tested on the methanol−ethane binary system.

Composite activated carbon monoliths were prepared from polyfurfuryl alcohol-impregnated compressed expanded graphite (CEG) blocks by pyrolysis at 923 K followed by steam activation at 1073 K. The porous texture of these materials was analysed from physical adsorption measurements of N 2 at 77 K and CO 2 at 273 K. Pyrolysis gives rise to a nitrogen surface area higher than for many conventional carbonised precursors of active carbons. Activation develops even more the porosity. At low burn-offs, there is principally creation of new pores (including ultramicropores). At higher burn-offs (of the order of 40%), opening of preexisting pores takes place. The materials obtained are essentially microporous and exhibit a rather narrow pore size distribution.

A few thousand (2,612) seeps are releasing microbial methane bubbles from the seafloor at the Aquitaine Shelf edge (Bay of Biscay) at shallow water depths (140–220 m). This methane contributes to the formation of meter‐scale subcircular carbonate structures, which are (sub)outcropping over 375 km2. Based on in situ flow rate measurements and acoustic data, and assuming steady and continuous fluxes over time, the methane entering the water column is estimated at 144 Mg/yr. Microbial methane circulation has been ongoing for at least a few thousand years. This discovery highlights the importance of microbial methane generation, disconnected from deep thermogenic sources and gas hydrates, at continental shelves. The shelf edge may be viewed as a focus area for methane circulation and release and related diagenesis, all having an impact on the shaping of continental shelves and potentially on the oceanic and atmospheric carbon budget. At the Aquitaine Shelf of the Bay of Biscay (Northeast Atlantic Ocean), the recent acoustic, chemical, and visual investigations of microbial methane release at the seafloor have led to the discovery of a vast fluid system. This methane escapes as bubbles from the seafloor into the seawater at 2,612 sites, all located at shallow water depths (140–220 m) along the edge of the continental shelf. Methane‐derived authigenic carbonates that are by‐products of gas seepage cover the (sub)seafloor over a large area of 375 km2. These carbonates form subcircular meter‐scale pavements and mounds, less than 2 m in height above the surrounding seafloor. Based on the growth rate of authigenic carbonates, it can be inferred that methane circulation has occurred for at least a few thousand years. The amount of methane released from the Aquitaine Shelf seafloor into the water column, estimated at 144 t/yr, questions the fate of the methane in the ocean and its possible passage to the atmosphere with therefore consequent potential contribution to the oceanic and atmospheric carbon budget over time. Up to 2,612 gas bubbling sites at the Aquitaine Shelf edge release 144 Mg/yr of microbial methane into the water columnMethane‐derived authigenic (sub)outcropping carbonates cover 375 km2Methane‐rich fluids have been circulating for at least a few thousand years