One of the most effective methods used in oilfield operations to prevent or limit scale formation is the use of precipitation squeeze treatments. A fundamental understanding of scale inhibitor precipitation is important in designing squeeze treatments in oilfield. Diethylentrilopentrakis (methylenephosphonic acid) (DTPMP) and Aminotri (methylenephosphonic acid) (ATMP), two scale inhibitors used in the petroleum industry were used as model inhibitors in this study. Inhibitor concentration, solution pH and the presence of salts in the produce fluids were found to have a significant impact on the placement of scale inhibitor and result in the formation of precipitates with markedly different properties. The amount of inhibitor precipitated decreases with the addition of Mg suggesting that the presence of Mg decreases the effectiveness of Ca-Inhibitor precipitation. A model of induction time was applied to inhibitor precipitation. Long induction times allow transport of the inhibitor fluids without inhibitor precipitation and damage to near-wellbore regions. The competitive reaction among the soluble salts in the formation water with the scale inhibitor was found to delay the precipitation rate of scale inhibitors. The nucleation kinetics of Ca-ATMP is accurately described by classical nucleation theory. The presence of different salts such as LiCl, NaCl, KCl and MgCl2 in solution was found to increase the surface free energies, thereby delaying the inhibitor nucleation and growth.

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