Salt Compression Research Articles

Jurassic raft tectonics in the northeastern Gulf of Mexico

The northeastern Gulf of Mexico is dominated by the 900–1800-m Florida Escarpment, which forms the bathymetric expression of the Cretaceous carbonate shelf edge. Outboard of the escarpment lies a region of salt-detached raft blocks, which are closely analogous to type examples in the Kwanza Basin, Angola, in terms of structural style, scale, and amount of extension. We undertook the first detailed structural interpretation of an emerging petroleum exploration province. The rafts detached and translated basinward by gravity gliding on the autochthonous Louann salt in the late Jurassic to early Cretaceous. The Upper Jurassic source rock (lime mudstones) of the Smackover Formation and eolian sandstone reservoir intervals of the Norphlet Formation are structurally segmented and entirely contained within the raft blocks. The rafts are separated by salt ridges and/or extensional fault gaps containing expanded uppermost Jurassic and lower Cretaceous strata of the Cotton Valley Group. The main episode of rafting occurred after deposition of the Smackover and Haynesville Formations and broke the Jurassic carbonate platform into raft blocks 2–40 km in length, which were then translated 25–40 km basinward from their original position. Map-view restoration of the raft blocks suggested a minimum extension of 100%, with basinward transport directions indicating a radial divergence of rafts. In the north of the study area, the transport direction was westerly, whereas in the south, translation was southerly. This pattern, which mimics the Florida Escarpment, suggested that the morphology of the Jurassic slope controlled the style of gravitational tectonics and the location of subsequent Cretaceous carbonate buildups. As with other linked systems on mobile substrates, the observed extension and translation must be balanced by downdip contraction. In the case of the northeastern Gulf of Mexico, the contraction is largely cryptic, being accommodated by salt evacuation, compression of salt walls/stocks, and possibly open-toed canopy advance.

Molal volumes and compressibilities of salts in seawater

Changes in the partial molal volumes (ΔV¯∗) and compressibilities (Δκ¯∗) for chemical reactions in seawater ΔV∗=∑iV¯∗(products)-∑iV¯∗(reactants)Δκ∗=∑iκ¯∗(products)-∑iκ¯∗(reactants) can be used to estimate the effect of pressure on ionic equilibria constants (KP/K0) ln(K∗P/K∗0)=(ΔV∗/RT)P-0.5(Δκ∗/RT)P2 where R and T have their normal meaning and P is the applied pressure (bar). The superscript * is used to denote values for an ionic media not water. In this paper, the partial molal volumes and compressibilities of a number of salts have been measured in seawater at 25°C. These results have been used to determine the conventional partial molal volumes and compressibilities (V¯∗(H+) and κ¯∗(H+)=0) for a number of ions (H+, Li+, Na+, K+, Rb+, Cs+, NH4+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Cl−, Br−, I−, OH−, NO3-, HCO3-, SO22- and CO32-) in seawater at 25°C. The values of the partial molal volume V¯∗ for F−, CO32- and SO42+ are higher in seawater than 0.725m NaCl at the same ionic strength (SP=35.00 and SA∼35.165g/kg). This is due to the formation of strong complexes with Mg2+ and Ca2+ and the release of water molecules upon the formation of the complexes. The first measurements of κ¯∗ of salts in seawater are compared to the results in 0.725m NaCl. Since the values of κ¯∗ are similar in the two media, one can use the values in 0.725m NaCl for seawater calculations. Correlations of the values of V¯∗ and κ¯∗ in seawater and 0.725m NaCl have been developed to estimate the values for unknown ions in seawater. These results can be used to estimate the effect of pressure on ionic equilibria in the deep ocean.

Salinity Controlled Vesicle Formation and Growth in Aqueous Mixture of Aerosol OT/Triton X‐100

Mixed vesicles can be formed spontaneously from aqueous mixture of the double‐tailed anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) and the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X‐100) under the inducement of salt, the formation mechanism of which should be attributed to the compression of salt on the electric bilayers of the head groups. The stability and the polydispersity of the vesicles are superior to single‐component AOT vesicles, which can be proved by the TEM image and visual observation. The vesicle region was presented in a pseudo‐ternary diagram of AOT/TX‐100/brine. The size of the vesicle was measured using dynamic light scattering. It is found that the vesicle size increases with the salinity but decreases with the content of TX‐100 in the mixture at the same salinity. Especially, the vesicle size is independent of the surfactant concentration at fixed salinity.

Compressibility of Salts

AbstractThe mechanism of tablet compression of the chloride, bromide and iodide salts of sodium, potassium and ammonium was studied, by obtaining their force-displacement curves. The area under these curves, which represents the work done on the tableting mass during compaction, was calculated. The effect of duration of the compressive force, of applied pressure on tablet strength and of pressure on the relative volume for potassium bromide were also studied.