Mechanisms Of Mineral Scale Inhibition

Abstract

Mechanisms Of Mineral Scale Inhibition M.B. Tomson; M.B. Tomson Rice University Search for other works by this author on: This Site Google Scholar G. Fu; G. Fu Rice University Search for other works by this author on: This Site Google Scholar M.A. Watson; M.A. Watson Rice University Search for other works by this author on: This Site Google Scholar A.T. Kan A.T. Kan Rice University Search for other works by this author on: This Site Google Scholar Paper presented at the International Symposium on Oilfield Scale, Aberdeen, United Kingdom, January 2002. Paper Number: SPE-74656-MS https://doi.org/10.2118/74656-MS Published: January 30 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Tomson, M.B., Fu, G., Watson, M.A., and A.T. Kan. "Mechanisms Of Mineral Scale Inhibition." Paper presented at the International Symposium on Oilfield Scale, Aberdeen, United Kingdom, January 2002. doi: https://doi.org/10.2118/74656-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Oilfield Scale Conference and Exhibition Search Advanced Search AbstractThe adsorption and desorption potential of inhibitors to crystal nuclei has never been determined at the extremely low, threshold levels that are known to inhibit nucleation. An extensive study of adsorption and desorption isotherms of four phosphonates on barite or calcite are tested over a wide range of solution conditions (0 - 1 M NaCl, 0 - 0.1 M Ca, 0 - 0.33 M sulfate, 4.6-6.4 pH). From these adsorption/desorption observations, it is proposed that the primary driving force for adsorption is related to simple hydrophobic repulsion from solution of a macro neutral molecule and not, as is generally presumed some specific inhibitor-surface interaction. A single isotherm may be derived from these vastly different adsorbent, adsorbate combinations after the solid phase concentration is normalized to per unit surface area and the solution phase concentration is normalized to the concentration of metal phosphonate concentrations. From the nucleation study, it is observed that the inhibitor needed to completely inhibit barite formation is approximately equal to 16% surface coverage. Equation to predict minimum inhibitor need is proposed based upon this model and compared with field observations. Brine chemistry of a specific well dictates the solution speciation of scale inhibitors and adsorption potential, thereby, that will determine the efficiency of inhibitor. Surprisingly, the range of predicted inhibitor concentrations is quite similar to what is observed in the field as a minimum effective dose, even though it was arrived at by a completely independent method of calculation.IntroductionScale formation in gas and oil wells is a common and persistent problem during production, treatment, transportation, and disposal of co-produced salt water; inhibition of this scale formation is a priority. The most common mineral scale materials, and the focus of this research, are: calcite (CaCO3); barite (BaSO4), gypsum and related calcium sulfates (CaSO4·xH2O, x=2,1/2,0), celestite (SrSO4), siderite (FeCO3), halite (NaCl), and zinc and iron sulfides (Zn/FeS). In addition, related hydrocarbon-based deposits include gas hydrates, waxes, alphaltenes, naphthenates, and sulfur. The primary focus of this research report is the formation and control of the sparingly soluble mineral scales. Most research on scale formation has focused on measuring and predicting the rate and amount of scale formation under different conditions of T, P, and brine composition. Earlier, the Rice University Brine Chemistry Consortium has spent several years examining nucleation and precipitation rates and continues to do so, but the focus of this research has been on the mechanism(s) of mineral scale inhibition. In fact, scale formation and inhibition are intimately related to each other, e.g., a rule of thumb is that scale inhibitors are typically insoluble salts of one of the mineral lattice ions.Rates of nucleation and crystal growth in the absence of specific inhibitors are normally related to the mineral saturation ratio (e.g., SR(calcite) = {Ca2++{CO32-}/Kspcalcite) or the logarithm of the saturation ratio, called the saturation index, SI. Thermodynamics provides several very specific guidelines, or suggestive equations, for nucleation and crystal growth, and these equations have been known for over a century. There is no equivalent set of fundamental principles that can be used to predict scale inhibition. There are some more-or-less intuitive notions that inhibitors must interact with the forming nuclei or the growing crystal in some manner. The nature, amount, or type of these interactions of the inhibitor with the crystal/nucleus surface can not now be predicted from any set of fundamental principles of thermodynamics or kinetics. Consequently, there is little agreement on how to model inhibition at the molecular or process level. This dearth of guiding theoretical laws is common to all forms of scale formation, not just in the oil-field produced fluids. Keywords: barite, isotherm, asphaltene inhibition, tomson, scale remediation, adsorption isotherm, induction time, nacl, asphaltene remediation, production chemistry Subjects: Production Chemistry, Metallurgy and Biology, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene This content is only available via PDF. 2002. Society of Petroleum Engineers You can access this article if you purchase or spend a download.