Influence of impurities on the creep of salt from the Palo Duro Basin

Mineralogy of deepwater Gulf of Mexico salt formations and implications for constitutive behavior

“…Although data were sparse, Pfeifle et al (1995) found that at 100°C (212°F) the steady-state stress exponent showed a strong correlation with anhydrite content. This is consistent with earlier work of Hansen et al (1987) who observed that increases in anhydrite content in salt reduce creep rates. Salt that contains clay is weaker than pure salt (Chan et al, 1996), because of the inability of clay to support any load, with resultant increased effective deviatoric stress on the load-carrying salt grains (the same effect would occur for small amounts of any another impurity, such as anhydrite).…”

Reinvestigation into Closure Predictions of Room D at the Waste Isolation Pilot Plant

“…The di↵erences obtained are usually small, as less than an order of magnitude di↵erence in the steady-state strain rate is generally observed. This result is in contrast to that obtained by Hansen et al (1988b). In their study using salt from the Palo Duro Basin, no influence of clay impurities on creep deformation was detected for impurity contents up to 25 percent."…”

“…In their study using salt from the Palo Duro Basin, no influence of clay impurities on creep deformation was detected for impurity contents up to 25 percent." Salt creep's sensitivity to moisture may be one potential reason for the di↵erence between the Senseny (1986) and Hansen et al (1988b) results. According to Senseny (1986), "[t]he argillaceous salt was sealed after drilling, but the clean salt was not."…”

Salt Mechanics Primer for Near-Salt and Sub-Salt Deepwater Gulf of Mexico Field Developments

“…There is some evidence to suggest that such variability is caused by differences in salt chemistry, mineralogy, or other physical characteristics such as subgrain size, grain size distribution, or grain aspect ratio. For example, Hansen et al (1987) The steady-state strain rate determined at a temperature of 373 K and a stress difference of 5 MPa is correlated with mean grain size (ρ = 0.96) and with grain aspect ratio (ρ = 0.89). For impure salts, at 373 K the steady-state stress exponent shows a direct correlation with both sodium and chlorine (~0.90).…”

“…There has been some evidence to suggest that such variability is caused by differences in salt chemistry, mineralogy, or other physical characteristics such as subgrain size, grain size distribution, or grain aspect ratio. For example, Hansen et al (1987) demonstrated that increases in anhydrite content in salt reduce creep rates.…”