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

Abstract

Monomers of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS®), N,N–dimethyl acrylamide (NNDMA) and acrylic acid (AA) were grafted on humic acid as backbone by aqueous free radical copolymerization in such a manner that a graft copolymer possessing lateral terpolymer chains was obtained. Molar ratios between AMPS®, NNDMA, and AA were found to be 1 : 1.54 : 0.02 and the ratio between backbone and graft chain was 20 : 80 wt %. The synthesized fluid loss additive (FLA) was characterized by size exclusion chromatography (SEC), charge titration, and Brookfield viscometry. Thermogravimetric and SEC analysis revealed stretched backbone worm architecture for the polymer whereby humic acid constitutes the backbone decorated with lateral graft chains. Grafting was confirmed by SEC data (Rg) and by ineffectiveness of a blend of AMPS®‐NNDMA‐AA copolymer with humic acid. Their performance as high temperature FLA was studied at 150°C by measuring static filtration properties of oil well cement slurries containing 35% bwoc of silica fume and 1.2% bwoc AMPS®‐co‐itaconic acid retarder. At this temperature, 1.0% bwoc graft copolymer achieves API fluid loss value of 40 mL, thus confirming high effectiveness. The graft copolymer viscosifies cement slurries less than other common synthetic FLAs. The working mechanism of the graft copolymer was found to rely on adsorption onto surface of hydrating cement, as was evidenced by adsorption and zeta potential measurements. Adsorption is hardly affected by temperature and results in constriction of the filter cake pores. The study provides insight into performance of cement additives under the harsh conditions of high temperature and high pressure. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of molecular flexibility on the rheological and filtration properties of synthetic polymers used as fluid loss additives in water-based drilling fluid

“…At present, many modications of high temperature uid loss additives are based on AMPS multicopolymers. [14][15][16] In recent decades, research has considerably enriched our knowledge about the mechanisms behind how these synthetic polymers prevent uid loss. It has shown that synthetic polymers as uid loss additives contain at least two groups: an adsorption group and a hydration group.…”

Synthesis and characterization of SSS/HAM/AA terpolymer as a fluid loss additive for oil well cement

“…For example, premature dehydration of the cement slurry pumped along the porous formation can result in poor slurry properties (i.e., high viscosity, short thickening time, etc. ), excessive density increase and annulus bridging, or even cause the cement job complete failure . Therefore, the cement job need FLA to add to the oil‐well cement slurry and prevent water loss from the slurry …”

Preparation and performance of AMPS/AA/DMAA/SA copolymer as a filtrate reducer for oil well cementing

“…described a graft copolymer which comprised side chains connected to the backbone by aqueous free radical copolymerization. The backbone was humic acid, and the lateral terpolymer chains contained the monomers of sodium 2‐acrylamido‐2‐methylpropane sulfonate, N,N‐dimethyl acrylamide, and acrylic acid . A new spherical microparticles of poly(methyl methacrylate‐co‐vinyl acetate) was synthesized by Nunes et al .…”