Cement Slurry Design for High-Pressure, High-Temperature Wellbores Using Polymer Nanocomposite: A Laboratory Scale Study Based on the Compressive Strength and Fluid Loss

Abstract

For the successful cementing operation of petroleum wells, the design of cement slurry plays a crucial role. Cement slurry must address the requirements of higher compressive strength; lower fluid loss; durability; and high-pressure, high-temperature (HPHT) challenges. A large number of chemical additives in cement slurry affects the required rheological properties; therefore, the development of multifunctional additives is desirable. In the present study, this problem has been addressed with the use of a single polymeric nanocomposite additive to address multiple requirements. A novel tetrapolymer nanocomposite (TPN) was synthesized in the laboratory by in situ polymerization in the presence of zinc oxide nanoparticles. Four monomers, namely acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, vinyl phosphonic acid, and N-[3-(dimethylamino)propyl] methacrylamide, were selected for the in situ polymerization reaction. The synthesized product was characterized using 1H NMR, FTIR, and TGA techniques. Laboratory-synthesized TPN was mixed in varying concentrations in the cement slurry as an additive. The performance of the enhanced cement slurry was then evaluated by performing compressive strength analysis and a filtration test using an ultrasonic cement analyzer and an HPHT filter press, respectively. These experimental analyses show that the addition of the TPN improved the compressive strength of the cement slurry and, at the same time, abbreviated the fluid loss, which is desired for efficient cementing operation. With the addition of 1.0% by weight of cement (BWOC) of TPN, the compressive strength increased by ∼136% compared with base cement. Additionally, this small dosage also reduced HPHT fluid loss by ∼67%. This experimental investigation shows that the novel TPN additive is capable of improving the efficacy of oil-well cement slurry at high-temperature conditions without compromising on thickening time because the additive also improved the waiting-on-cement time for HPHT conditions.