Working mechanism of a high temperature (200°C) synthetic cement retarder and its interaction with an AMPS®‐based fluid loss polymer in oil well cement

Abstract

A copolymer comprising of 2-acrylamido-2methyl propane sulfonic acid (AMPS V R ) and itaconic acid (molar ratio 1 : 0.32) was synthesized by aqueous free radical polymerization and probed as high temperature retarder for oil well cement. Characteristic properties of the copolymer including molar masses (M w and M n ), polydispersity index and anionic charge amount were determined. The copolymer possesses a M w of $ 2 Â 10 5 g/mol and is highly anionic. HT/HP consistometer tests confirmed effectiveness of the retarder at temperatures up to 200 C. The working mechanism of NaAMPS V R -co-itaconic acid was found to rely exclusively on its huge calcium binding capacity (5 g calcium/g copolymer). It reduces the amount of freely dissolved, nonbound calcium ions present in cement pore solution and thus hinders the growth of cement hydrates because of lack of calcium. The value for the calcium binding capability is 46 times higher than the stoichiometric amount per ACOO À functionality. Con-sequently, calcium also coordinates to other donor atoms present in the retarder. NaAMPS V R -co-itaconic acid also adsorbs onto cement, as was evidenced by TOC analysis of cement filtrates, zeta potential measurement and decreased rheology of cement pastes. However, adsorption plays no role in the retarding mechanism of this copolymer. Combination of NaAMPS V R -co-itaconic acid retarder with a common CaAMPS V R -co-NNDMA fluid loss additive (FLA) revealed that competitive adsorption on cement between these two admixtures occurs. The retarder fills interstitial adsorption sites on cement located between those occupied by the larger FLA molecules. In consequence, fewer amounts of CaAMPS V R -co-NNDMA can adsorb and its effectiveness is reduced.

Preparation of amphoteric polycarboxylate superplasticizers and their performances in cementitious system

“…The adsorbed PC molecules on cement surface, which are usually anionic charged polymers, create both electrostatic repulsive forces and steric hindrance due to the long poly (ethylene oxide) (PEO) side chains. On the other hand, it has been understood that the retardation effect of PCs originates from the two facts: (1) the adsorbed PC layers hinder the diffusion of water and ions at the cement‐solution interface; (2) the COO − groups in PCs molecules may form complexes with Ca 2+ in aqueous phase and thus inhibit the nucleation and growth of Ca‐containing hydration products. It has widely accepted that the surfaces of silicate phases (C 3 S, C 2 S) and calcium silicate hydrates (CSH) are negatively charged, whereas the surfaces of the aluminate phases (C 3 A, C 4 AF) are positively charged .…”

A Review of Synergistic and Antagonistic Effects Between Oilwell-Cement Additives

“…A study on the working mechanism of an NaATBS-itaconic acid copolymer as an HT stable retarder for oilwell cement revealed that its working mechanism is based on adsorption on cement (Tiemeyer and Plank 2012). Thus, a potential to perturb the effectiveness of other additives that also work by adsorption was foreseen.…”

“…This effect is surprising because, when used individually, dispersants such as PMS typically increase fluid loss. This paper presents a synopsis of the results obtained from the study of several common cement-admixture combinations (Plank et al 2007(Plank et al , 2008(Plank et al , 2010Recalde Lummer and Plank 2012;Bülichen and Plank 2012;Tiemeyer and Plank 2012). It attempts to categorize the different types of interaction found there on the basis of the fundamental mechanisms underlying those interactions.…”

Synthesis, effectiveness, and working mechanism of humic acid‐{sodium 2‐acrylamido‐2‐methylpropane sulfonate‐co‐N,N‐dimethyl acrylamide‐co‐acrylic acid} graft copolymer as high‐temperature fluid loss additive in oil well cementing

“…Additionally, the graft copolymer is fully compatible and effective with a synthetic retarder based on AMPS®‐ co ‐itaconic acid. They do not perturb each other, which differentiates it from other cement fluid loss additives such as e.g., CaAMPS®‐ co ‐NNDMA 37…”

“…They do not perturb each other, which differentiates it from other cement fluid loss additives such as e.g., CaAMPS V R -co-NNDMA. 37 The adsorptive mechanism of the graft copolymer is highly surprising since it is well known that ettringite, a cement hydrate formed from tricalcium aluminate and calcium sulfate present in cement, presents the main mineral for adsorption of anionic admixtures. 38 However, ettringite is not stable at temperatures exceeding $ 80 C and therefore is practically absent at 150 C which was the test temperature here.…”