Mechanistic Investigation of Adsorption Behavior of Two Scale Inhibitors on Carbonate Formations for Application in Squeeze Treatments

Abstract

Understanding the mechanisms of scale inhibitor (SI) retention in carbonate formations is key to designing efficient SI "squeeze" treatments in oil reservoirs. By performing "apparent adsorption" experiments, this paper demonstrates that a coupled adsorption/precipitation (Γ/Π) retention mechanism dominates in calcite and limestone for two widely applied scale inhibitors, DETPMP and PPCA. Precipitation was a more dominant retention mechanism at both initial pH values (pH 0 4 and 6) and T = 80 and 95 °C for both SIs. At 95 °C, the pure adsorption (Γ) region only extends up to [SI] ∼ 100 ppm, above which precipitation (Π) dominates. At lower temperatures (T = 80 °C), the solubility of the SI−M 2+ complex increases, resulting in less precipitation. The apparent adsorption results are supplemented by measuring the corresponding solution [Ca 2+ ], pH values in solution, and environmental scanning electron microscopy/energy dispersive X-ray analysis (ESEM/EDX) and particle size analysis (PSA), which give us a full mechanistic explanation of our results. For DETPMP, the retention increased as the solution pH increased, while retention of PPCA increased as the test pH decreased. Moreover, DETPMP was retained more than PPCA due to their differences in chemistry. Furthermore, the retention of both SIs was greater for the limestone sample due to Fe 2+ traces enhancing the precipitate of SI−M 2+ .

Surface Chemistry of Phosphonate Scale Inhibitor Retention Mechanisms in Carbonate Reservoirs

“…The bottle cap was fastened and the bottle was shaken. The bottles were then placed in a preheated oven at the appropriate temperature ( T = 95 °C). The bottle caps were checked for tightness after1 h and refastened if required. After 24 h, the bottles were removed from the oven. The contents of each bottle were vacuum-filtered through separate 0.2 μm membrane filters, with the filtrate and supernatant retained for analysis. The resultant supernatant was left to cool for ∼24 h before the pH was measured. In addition, 1 mL was removed by pipet and diluted with 9 mL of a 1% sodium chloride solution and then analyzed via ICP-OES for the ion concentrations of phosphorus, calcium, magnesium, and lithium. ESEM/EDX was performed on the collected solid phases for both the precipitate as well as the mineral, in order to analyze the surface of the calcite/dolomite grains and any bulk precipitate formed. , …”

“…ESEM/EDX was performed on the collected solid phases for both the precipitate as well as the mineral, in order to analyze the surface of the calcite/dolomite grains and any bulk precipitate formed. , …”

“…This process is described by an adsorption isotherm, Γ­( C ), and several forms of this isotherm (e.g., Langmuir, Freundlich, etc.) have been shown to be adequate to describe the adsorption/desorption process for SIs in both the laboratory and in the field. − Precipitation (Π) occurs when the SI molecule precipitates out of the solution because of the formation of an inhibitor/Ca complex. This SI/Ca complex is a sparingly soluble salt, denoted SI_Ca n , where the subscript n denotes the stoichiometry of the number of Ca molecules, relative to the number of SI molecules.…”

Review of Synthesis and Evaluation of Inhibitor Nanomaterials for Oilfield Mineral Scale Control

“…Obviously, it is of great economic and operational significance to extend the squeeze lifetime (Vazquez et al, 2013(Vazquez et al, , 2014. With regard to the retention mechanism of the inhibitors, some scholars suggest that the inhibitors are surface adsorbed by formation materials, and the presence of divalent metals in formation facilitates the surface adsorption via complexation (Sorbie et al, 1997;Vazquez et al, 2011;Jarrahian and Sorbie, 2020). As a consequence, the release process of the inhibitor into the production fluid during the resumed production is controlled by the desorption of the inhibitor from the formation surface (Vazquez et al, 2011).…”

“…Mineral scale (hereafter referred to as "scale") is the hard inorganic crystal deposit from the water phase (Cowan and Weintritt, 1976). In the past few decades, extensive research efforts have been made in both academia and industry to control scale threats, especially for oilfield operations (Frenier and Ziauddin, 2008;Kelland, 2014;Hu and Mackay, 2017;Ribeiro et al, 2017;Ishkov et al, 2019). The primary strategy for scale control replies on chemical inhibition using scale inhibitor chemicals (Vazquez et al, 2016.…”