Scale-Inhibitor Consumption in Long-Term Static Barium Sulfate Inhibition Efficiency Tests

Abstract

In typical bulk barite inhibition-efficiency (IE) experiments testing scale inhibitors (SIs), the IE is determined by comparing the concentrations of the barium ion in the mix to that in an uninhibited "blank" solution. That is, [Ba 2þ ] vs. time is monitored for both a blank and an inhibited solution. The fate of the SI itself over this test time period is rarely monitored, although this can give some important insights into the inhibition mechanism. This paper presents a series of long-term (up to 96 hours) barium sulfate static IE experiments in which both the supernatant SI concentration, [SI], and [Ba 2þ ] are assayed at multiple sampling times after initial mixing of seawater (SW) and formation-water (FW) brines. In standard IE tests to determine SI minimum inhibitor concentration (MIC), sampling is normally carried out at 2 hours and 22 hours only. The long-term IE experiments described in this paper involve up to eleven sampling times, typically at t ¼ 0.5, 1, 2, 3, 4, 5, 6, 22, 48, 72, and 96 hours after mixing.The aim of this type of experiment is to determine the fate of the SI over time and to determine whether the IE and percentage of SI (%SI) in solution vs. time profiles correlate with each other. Clearly, SI removed from solution is consumed into the forming barium sulfate lattice in the barite precipitate. IE and solution SI often continue to decline beyond 22 hours, up to 96 hours after the mixing stage. In these experiments, the SI concentration is set at a pre-2-hour MIC threshold concentration, such that the IE and %SI consumption profiles will both decline sufficiently over time, possibly even as early as one-half hour after mixing. The SI consumption profiles obtained by testing an extensive range of phosphonate and polymeric SIs are compared and discussed. Normally, a phosphorus-containing SI is selected for evaluation to facilitate assay of SI by means of inductively coupled plasma (ICP) spectroscopy. However, some novel results are also presented in which selected polymeric SIs were assayed by non-ICP analytical techniques. We interpret this extensive series of SI lattice-consumption experiments in terms of the mechanisms of barite inhibition and Type 1/Type 2 SI classifications presented in previous papers (Shaw et al. 2012a, b). The relevance and practical application of these findings are also discussed.

Scale inhibitors

“…However, the fate of the scale inhibitors is rarely monitored, although this can give some important insights into the inhibition mechanism [75]. However, the fate of the scale inhibitors is rarely monitored, although this can give some important insights into the inhibition mechanism [75].…”

“…The aim of this type of experiment was to determine the fate of the inhibitor over time and to determine whether the inhibition efficiency and percentage of the inhibitor in solution correlate [75].…”

Influence of Terpolymer Based on Amide, Carboxylic, and Sulfonic Groups on the Barium Sulfate Inhibition

“…5,24,30,31 In addition, their effectiveness may also be influenced by external factors such as temperature, pH, ionic strength, flow rates, shear forces, nucleation sites, and residence times. 12,13,15,16,21,22,32 Typically, an effective scale inhibitor contains at least one of the following functional groups: carboxyl, −COOH; sulfonic, −HSO 3 ; ester, −COOR; phosphonic acid, −PO 3 H 2 , etc. 5,24,33,34 The development of copolymers has been increasing progressively, since it is possible to incorporate two or more of those functional groups on the same polymeric chain and thus possibly improve inhibitor performance.…”

“…However, the maximum thermodynamic scaling tendency (SR), which is essentially the driving force to reach equilibrium precipitation, is at 60/40 SW/FW mix. Therefore, in order to inhibit the formation of barium sulfate, a lower concentration of scale inhibitor will be required for the 10/90 SW/FW mix, since this system has a lower scaling tendency; whereas a much higher quantity of SI would be required to inhibit the 60/40 SW/FW mix, since this case has the highest scaling tendency for this system. − …”

“…Polymers can be produced from organic raw, coming from the petrochemical industry, and they are extensively used in oil production for many purposes including scale inhibition. ,,− Many polymeric scale inhibitors have been developed over the years to be applied in oilfields. More recently, green chemicals have also been tested, such as proteins and pectins. , The performance of the polymeric inhibitors is dependent on the functional groups present in the molecules, the molar mass, and their charge density. ,,, In addition, their effectiveness may also be influenced by external factors such as temperature, pH, ionic strength, flow rates, shear forces, nucleation sites, and residence times. ,,,,,, …”