Investigation of Brine pH Effect on the Rheological and Viscoelastic Properties of HPAM Polymer for an Optimized Enhanced Oil Recovery Design

Effect of Temperature and Alkali Solution to Activate Diethyl Carbonate for Improving Rheological Properties of Modified Hydroxyethyl Methyl Cellulose

The applications of cellulose ethers in the petroleum industry represent various limitations in maintaining their rheological properties with an increase in both concentration and temperature. This paper proposed a new method to improve the rheological properties of hydroxyethyl methyl cellulose (HEMC) by incorporating diethyl carbonate (DEC) as a transesterification agent and alkali base solutions. Fourier transform infrared (FTIR) analysis confirmed the grafting of both composites onto the HEMC surface. The addition of sodium hydroxide (NaOH) improved the stability of the polymeric solution as observed from ζ-potential measurement. Shear viscosity and frequency sweep experiments were conducted at concentrations of 0.25-1 wt % at ambient and elevated temperatures ranging from 80-110 °C using a rheometer. In the results, the increase in viscosity at specific times and temperatures indicated the activation of DEC through the saponification reactions with alkali solutions. All polymeric solutions exhibited shear-thinning behavior and were fitted well by the Cross model. NaOH-based modified solution exhibited low shear viscosity compared to the DEC-HEMC solution at ambient temperature. However, at 110 °C, its viscosity exceeded that of the DEC-HEMC solution due to the activation of DEC. In frequency sweep analysis, the loss modulus (G″) was greater than the storage modulus (G') at lower frequencies and vice versa at higher frequencies. This signifies the viscoelastic behavior of modified solutions at 0.50 wt % and higher concentrations. The flow point (G' = G″) shifted to a low frequency, indicating the increasing dominance of elastic behavior with the rising temperature. At 110 °C, the NaOH-based modified solution exhibited both viscous and elastic behavior, confirming the solution's thermal stability and flowability. In conclusion, modified HEMC solution was found to be effective in controlling viscosity under ambient conditions, enhancing solubility, and improving thermal stability. This modified composite could play a significant role in optimizing viscoelastic properties and fluid performance under challenging wellbore conditions.

Advancing Dimethacrylate Dental Composites by Synergy of Pre-Polymerized TEGDMA Co-Filler: A Physio-Mechanical Evaluation

Dental resin composites (DRCs) have gained immense popularity as filling material in direct dental restorations. They are highly valued for their ability to closely resemble natural teeth and withstand harsh oral conditions. To increase the clinical performance of dental restorations, various fillers are incorporated into DRCs. Herein, the effect of incorporating pre-polymerized triethylene glycol dimethacrylate (P-TEGDMA) as a co-filler in varying proportions (0%, 2.5%, 5%, and 10% by weight) into bisphenol A-glycidyl methacrylate (BisGMA)/TEGDMA/SiO2 resin composite was investigated. The obtained DRCs were examined for morphology, rheological properties, degree of crosslinking (DC), Vickers microhardness (VMH), thermal stability, and flexural strength (FS). The results revealed that SiO2 and P-TEGDMA particles were uniformly dispersed. The introduction of P-TEGDMA particles (2.5 wt.%) into the resin composite had a remarkable effect, leading to a significant reduction (p ≤ 0.05) in complex viscosity, decreasing from 393.84 ± 21.65 Pa.s to 152.84 ± 23.94 Pa.s. As a result, the DC was significantly (p ≤ 0.05) improved from 61.76 ± 3.80% to 68.77 ± 2.31%. In addition, the composite mixture demonstrated a higher storage modulus (G') than loss modulus (G″), indicative of its predominantly elastic nature. Moreover, the thermal stability of the DRCs was improved with the addition of P-TEGDMA particles by increasing the degradation temperature from 410 °C to 440 °C. However, the VMH was negatively affected. The study suggests that P-TEGDMA particles have the potential to be used as co-fillers alongside other inorganic fillers, offering a means to fine-tune the properties of DRCs and optimize their clinical performance.

Experimental Investigation of a Self-adaptive Thickening Polymer Performance under High-Temperature-High-Salinity Reservoir Conditions

A polymer flooding workflow was developed to diminish polymer degradation and minimize formation damage under high-temperature-high-salinity reservoir conditions by using a shear-thickening polymer (SAP) prepared in engineered waters. First, rock characterization, fluid-fluid analysis, and formation damage tests were conducted to shortlist the potential formulations of polymer solutions based on higher viscosity and less formation damage. Second, polymer core flooding experiments were conducted under reservoir conditions to investigate the performance of candidate polymer solutions on oil displacement efficiency (DE). For the first time, the compatibility between SAP and engineered water was systematically tested. The factors affecting bulk rheology, polymer retention, and oil DE, including polymer concentration, polymer type, salinity, and hardness, were experimentally investigated and compared with regular partially hydrolyzed polyacrylamide (HPAM). Results showed that compared with HPAM, the SAP solution led to lower formation damage and overall higher oil DE, especially in the first 0.4 pore volume of polymer injection. When using SAP prepared in twice-diluted and hardness-stripped seawater under low-salinity formation brine conditions, the DE was the highest (69.04%). The formation damage was reduced when the salinity and hardness of the base fluid were lower, whereas stripping the hardness had a more pronounced effect on reducing formation damage. The improved oil recovery potential due to the shear-thickening feature of SAP solutions and their better compatibility with engineered water compared to regular HPAM has been proven in this study. It was also found that the lower salinity and hardness of the engineered water further stimulated the enhanced oil recovery potential of SAP solutions. The contribution of this work relies on revealing how SAP prepared in different engineered waters affects incremental oil DE under harsh reservoir conditions based on experimental evidence and mechanism analysis. The novelty of this work lays the foundation for investigating the potential application of SAP on a pilot scale.

Testing and Evaluation of the Emulsifying Properties of Compound Oil Displacement Agents

Aiming at the phenomenon that the emulsification degree of the composite oil displacement agents affects the recovery factor, composite oil displacement agents of the P/S binary system and the A/S/P ternary system were taken as research objects. Emulsion particle size and stability were tested and evaluated, and the effects of the surfactant and alkali content on the emulsification degree of emulsion were investigated. The concept of the emulsification stability index and its measuring method were put forward, and a method was used to test and evaluate the emulsification stability of the emulsion. The results showed that the emulsion formed by the ternary system had the smallest average particle size, the best stability, and the best emulsification stability. The binary composite system was second, and the polymer solution did not form an emulsion. The emulsification stability index method could effectively quantify the emulsification degree of the emulsion. Within a certain range, the increase of the surfactant and alkali content in the composite oil displacement agent was beneficial to the improvement of the emulsification degree of the emulsion.