Inhibition of Mineral Scale Precipitation by Polymers

Abstract

The inhibitory efficiency of polymeric inhibitors against the precipitation of common mineral scales in industrial processes could be described quantitatively using a semi-empirical model based on nucleation theory and laboratory experimental observations. The minimum effective inhibitor concentration (C_inh, mg/1) which is needed to prevent precipitation at a given degree of supersaturation can be estimated by: C_inh = (l/b_inh) log (f_St_p/t₀), where b_inh is the efficiency of the inhibitor (l/mg), t_p is the inhibition time or protection time needed for the system (seconds), t₀ is the nucleation induction period for the mineral at a given condition in seconds, and f_S is the safety factor (e.g., 2). Model parameters have been measured for typical scale minerals such as calcite and barite with eight scale inhibitors which have been commonly used in industrial processes, including polyacrylates and their derivatives (PAA, SPA, and PPCA) and poly-phosphonates (HEDP, NTMP, HDTMP, DTPMP, and BHPMP). This semi-empirical model has been demonstrated to be accurate in predicting the minimum effective inhibitor concentrations needed to protect a system from scaling comparing to both laboratory experimental simulation results using a high-temperature/high-pressure flow-through apparatus and preliminary observations in oil and gas production systems.