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

Abstract

Oilwell-cement slurries commonly incorporate several admixtures such as retarder, dispersant, fluid-loss additive (FLA), antifreewater agent, and defoamer. Between them, additive/additive interactions may occur that can result in incompatibilities and reduced performances (the most frequent case) or, oppositely, in improved effectiveness. Here, an overview of some synergistic and antagonistic effects between selected cement additives is presented. Four combinations of additives were tested and studied.First, the interaction between 2-Acrylamido-tertiary-butyl sulfonic acid-co-N,N-dimethylacrylamide (CaATBS-co-NNDMA) FLA and an NaATBS-co-itaconic acid retarder as well as welan gum, an anionic biopolymer applied as an antifree-water additive, was investigated. It was found that the retarder, which possesses a particularly high-anionic charge, reduces the effectiveness of the CaATBS-co-NNDMA FLA by decreasing its amount adsorbed on cement. Similarly, the anionic biopolymer can also negatively affect the effectiveness of the FLA through competitive adsorption, in which the biopolymer hinders the sufficient adsorption of the FLA on cement. The incorporation of stronger anchor groups (e.g., dicarboxylates or phosphonates) into the CaATBS-co-NNDMA FLA enhances its affinity for the surface of cement and thus renders it more robust against the negative impact from other admixtures.Second, the compatibility between an Na þ lignosulfonate (Na-LS) retarder and the CaATBS-co-NNDMA FLA was investigated. Here, surprisingly, a dual synergistic effect was found. Na-LS improves the fluid-loss performance of CaATBS-co-NNDMA, whereas the latter greatly enhances the retarding effectiveness of lignosulfonate. The experiments demonstrate exceptionally high compatibility of both admixtures. The positive effect is based on coprecipitation of both polymers, which enhances FLA adsorption on cement. At the same time, because of the thick adsorbed polymer layer, the dissolution of the clinker phases is hindered, resulting in the retardation of cement hydration.Finally, it was found that hydroxyethyl cellulose (HEC) and sulfonated formaldehyde polycondensate-based dispersants -such as poly melamine sulfonate (PMS) or acetone formaldehyde sulfite (AFS) -act synergistically; thus, the fluid-loss control provided by HEC is considerably improved. Dynamic light-scattering measurements revealed that, in the presence of those dispersants, the association of HEC molecules into large hydrocolloidal assemblies was greatly enhanced. Obviously, the increased ionic strength resulting from the polycondensate dispersants renders the nonionic HEC molecules less water-soluble and initiates their aggregation at an earlier stage. The larger hydrocolloidal polymer associates can plug filter-cake pores more effectively, thus reducing cement fluid loss.The study suggests that multiple additive/additive interactions can occur in oilwell cement. Understanding the underlying mechanisms can help both to avoid unwanted incompatibilities and to develop mitigation strate...

Cement additives

“…The synergistic and antagonistic effects between oilwell cement additives have been reviewed [85]. Oilwell cement slurries commonly incorporate several admixtures such as retarder, dispersant, fluid-loss additive, anti freeze water agent, and defoamer.…”

“…The incorporation of stronger anchor groups, for example, dicarboxylates or phosphonates, into the formulation enhances its affinity for the surface of cement and thus renders it more robust against the negative impact from other admixtures [85]. The incorporation of stronger anchor groups, for example, dicarboxylates or phosphonates, into the formulation enhances its affinity for the surface of cement and thus renders it more robust against the negative impact from other admixtures [85].…”

Adsorption Affinity of Linear and Aromatic Organic Anions Competing for Cationic Cement Surfaces

“…However, even in a binary mix of admixtures in a slurry, antagonistic or synergistic interference between admixtures is known to occur. 6 cement mixes. 5,7−9 In the first example, the anionic cement superplasticizer, sulfonated acetone-formaldehyde condensate (SAF, Table 1), antagonistically reduced the effectiveness of an anionic fluid-loss admixture, 2-acrylamido-t-butyl sulfonic acid (AMPSA)/N,N-dimethyl acrylamide (NN-DMA) copolymer, which also functions by adsorption onto cement particle surfaces.…”

“…It is commonly assumed that the reactivity of each admixture will exhibit its design properties when added in the slurry, with little to no interference from other admixtures in the mix. However, even in a binary mix of admixtures in a slurry, antagonistic or synergistic interference between admixtures is known to occur . Plank et al.…”

Effect of Newly Prepared Admixture on the Rheology and Early Hydration Characteristics of the Oil Well Cement Pastes

“…(1) Issue (1) Jan.2016 compatibility at high temperature/high pressure are still largely unexplored [7]. In the field of cement products, recent advances are related to the use of admixtures specially those of organic materials like polymers added in small quantities to modify and to enhance the properties of cement products [12]. Thus, the protective characteristics of oil well cements may be controlled by the addition of polymeric additives.…”