Precipitation of Calcium Carbonate in Porous Media in the Presence of n-Dodecane

Abstract

The precipitation and crystal growth of sparingly soluble salts are associated with scaling problems in oil and gas extraction processes. The presence of oleic phases and/or organic solvents added as inhibitors of the gas hydrates often complicates scale formation problems. The pore structure of the oil reservoir walls is of particular interest in the process of scale formation. In the present work the effect of the presence of n-dodecane in the crystallization of CaCO3 was investigated. The study was done in simulated one-dimensional porous media made of Plexiglas, in which supersaturated solutions of various supersaturation ratios (SRinitial) with respect to calcite were introduced. The growth of the precipitated crystals was continuously monitored by optical microscopy and calcium concentration monitoring. At high SRinitial values, larger numbers of small size crystals were grown, mainly near the oil–water interface. The presence of n-dodecane resulted in the reduction of the induction time preceding the appearance of CaCO3 crystals. The measured precipitation rates of CaCO3 were higher with increasing SRinitial values. The presence of n-dodecane in the supersaturated solutions, in the respective two-phase system, favored the stabilization of the thermodynamically less stable polymorphs of CaCO3 (aragonite, vaterite). Mapping analysis of the deposits polymorphs using Raman spectroscopy showed that the precipitation was not homogeneous along the flow channel at the experimental conditions of the present work.

Mineral Scaling in the Presence of Oil–Water Interfaces Combined with the Substrate’s Wettability Effect: From Batch to Microfluidic Experiments

“…In contrast to earlier findings, that higher SR values resulted in the formation of larger crystals in hydrophilic microchannels and the size of the crystallites obtained at S or was smaller (Figure ). This finding agrees with an earlier report on the precipitation of calcium carbonate in the larger size channel (length: 6 cm, width: 1 mm, and depth: 0.3 mm) made of plexiglass . The slopes of the curves in Figure were 1.099 ( R 2 = 0.993) for SR = 30.2 and 2.165 ( R 2 = 0.994) for SR = 10.5 in the presence of n -dodecane and 8.310 ( R 2 = 0.941) for SR = 30.2 and 2.951 ( R 2 = 0.959) for SR = 10.5, suggesting that the crystal growth rate of individual crystallites is lower in the presence of n -dodecane.…”

“…It may be suggested that the oil–water interface acted as nucleation sites because of the low interfacial tension which reduces the nucleation Gibbs free energy. The acceleration of crystal nucleation and growth in the presence of oil–water interfaces has also been reported in salt precipitation experiments performed in plexiglass channels . However, precipitation rates calculated in the absence of n -dodecane were higher than the corresponding rates for V Ro/a = 0.5 and lower than the rate for V Ro/a = 0.6 (Table ).…”

“…Earlier investigations of CaCO 3 precipitation in the presence of oil/water interfaces in larger plexiglass channels and in sand-packed beds showed acceleration of the nucleation in comparison with aqueous supersaturated solutions. The higher precipitation rates were attributed to the dodecane/water interfaces and to the lower value of interfacial tension, which reduced the free Gibbs energy for crystal nucleation. ,, CaCO 3 precipitation in plexiglass channels under S or conditions, yielded shorter induction times and larger number of smaller mean size crystals in comparison with the induction times and the corresponding crystallite mean size obtained at the corresponding SR values, in the absence of oil–water interfaces . Moreover, in addition to calcite, aragonite and vaterite were also identified with Raman spectroscopy, which were probably stabilized because of the varying interfacial energy conditions prevailing along the channel at the oil–water interfaces .…”

“…The higher precipitation rates were attributed to the dodecane/water interfaces and to the lower value of interfacial tension, which reduced the free Gibbs energy for crystal nucleation. ,, CaCO 3 precipitation in plexiglass channels under S or conditions, yielded shorter induction times and larger number of smaller mean size crystals in comparison with the induction times and the corresponding crystallite mean size obtained at the corresponding SR values, in the absence of oil–water interfaces . Moreover, in addition to calcite, aragonite and vaterite were also identified with Raman spectroscopy, which were probably stabilized because of the varying interfacial energy conditions prevailing along the channel at the oil–water interfaces . It is interesting to note that amorphous CaCO 3 has been detected to persist for longer times on hydrophilic surfaces than on hydrophobic surfaces.…”

Precipitation and Transformation of Vaterite Calcium Carbonate in the Presence of Some Organic Solvents

“…One of the factors which has a significant impact on the precipitation of calcium carbonate is the presence of additional substances [18][19][20]. Most often, these additives are not embedded in the formed crystals, but they affect the course of the reaction and the characteristics of the resulting product [1,21,22].…”