Synthesis of a hydrophobic associating polymer and its application in plugging spacer fluid

The high temperature of formation and multiple stages of leakage zone seriously affect the efficiency and safety of drilling and cementing operations. To improve leakage plugging quality before the cementing process, the hydrophobic associating polymer PHAAO was synthesized from acrylamide (AM), 2-acrylamide-2-methyl propane sulfonic acid (AMPS), and the long side-chain hydrophobic monomer octadecyl dimethyl allyl ammonium chloride (ODAAC) in this study. The structure and molecular weight of the polymer were characterized, and it was proved that the polymer has strong association properties and excellent heat resistance. Utilizing the bridge plugging principle, the polymer PHAAO was used with 36-mesh walnut shells and lignin fiber to form a compound plugging agent. This agent was added to spacer fluid to become a plugging spacer. API water loss tests and loading capacity tests under high temperatures show that the filter cake formed by the spacer fluid is dense. The sealing pressure of the spacer fluid on a 1 mm crack can reach 6.5 MPa at 160 °C, and it has good compatibility with cement slurry. A scanning electron microscopy (SEM) test was conducted to explore the membrane formation mechanism of the polymer. An ultra-low permeability membrane is formed on the surface of the filter cake from the spacer fluid due to the hydrophobic association and hydrogen bonding between the polymer and lignin fiber, thereby greatly reducing the loss of spacer fluid.

The polymer PHAAO not only has a strong hydrophobic association feature but also forms hydrogen bonds and cationic–π bonds with lignin fibers, combining with walnut shells enables the spacer fluid to show a strong plugging performance.

Effect of carboxylic group on the compatibility with retarder and the retarding side effect of the fluid loss control additive used in oil well cement

The retarding side effect and the compatibility with other additives are the main problems that limit the field application of the synthesized fluid loss control additive (FLCA). The effect of the type and content of carboxylic acid groups on the retarding side effect of FLCA and the compatibility between FLCA and the retarder AMPS-IA synthesized using 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and itaconic acid (IA) was studied in this paper. The type and content of carboxylic acid group have a great influence on the fluid loss control ability, the compatibility with retarder and the retarding side effect of FLCA. FLCA containing IA or maleic acid (MA) shows better compatibility with retarder than FLCA containing acrylic acid, but the retarding side effect of FLCA containing MA is weaker than that of FLCA containing IA. Thus, MA is the most suitable monomer for synthesizing FLCA having good compatibility with retarder AMPS-IA.

Synthesis, characterization and working mechanism of a novel sustained-release-type fluid loss additive for seawater cement slurry

Synthetic polymer fluid loss additive (FLA), an important type of admixture, was broadly applied in modern well cementation. However, the filter loss volume and fluidity of cement pastes containing polymer-FLA would deteriorate remarkably when sea water was used in mixing slurries instead of fresh water. In this study, a novel sustained-release-type fluid loss additive(S-FLA) was synthesized by means of anion-exchange intercalation reaction between an anionic type-copolymer and a calcium/aluminum type-Layered Double Hydroxide (Ca/Al-LDH). Based on the fluidity and compressive strength of experiments, it was found that in seawater mixing conditions, this composite material not only utilized its sustained release effect to significantly improve retention fluidity performance, but also the seed crystal effect of the Ca/Al-LDH effectively alleviated the declining in compressive strength of the slurries caused by the carboxyl group in the polymer. More interestingly, the realization of the slow release function increased actual adsorption capacity of the anionic polymer on the surface of cement hydrated particles, which made its controlling water loss effect was also better than that of the conventional FLA. The above advantages of this hybrid materials created the possibility to surmount the negative effect of electrolytes present in seawater, so as to provide some useful references for its practical application in the offshore well cement.

Preparation and properties of nanocomposites of β-cyclodextrin-functionalized polyacrylamide and its application for enhancing oil recovery

The introduction of nano-SiO₂can significantly improve the performance of β-cyclodextrin-functionalized polyacrylamide in various aspects.