# Synthesis of Linear Modified Siloxane-Based Thickeners and Study of Their Phase Behavior and Thickening Mechanism in Supercritical Carbon Dioxide

## TL;DR

Scientists created new thickeners to improve the performance of supercritical CO2 in oil drilling by increasing its viscosity and studying how they work.

## Contribution

The paper introduces novel siloxane-based thickeners and provides mechanistic insights into their performance in supercritical CO2.

## Key findings

- A 5 wt% thickener loading increased CO2 viscosity to 3.68 mPa·s.
- Molecular simulations revealed dissolution and thickening mechanisms of the thickeners in CO2.
- The thickeners showed excellent solubility and performance in high-pressure conditions.

## Abstract

To address critical limitations of ultra-low viscosity supercritical CO2 fracturing fluids, including excessive fluid loss and inadequate proppant transport capacity, a series of thickeners designed to significantly enhance CO2 viscosity were synthesized. Initially, FT-IR and 1H NMR characterization confirmed successful chemical reactions and incorporation of both solvation-enhancing and -thickening functional groups. Subsequently, dissolution and thickening performance were evaluated using a custom-designed high-pressure vessel featuring visual observation capability, in-line viscosity monitoring, and high-temperature operation. All thickener systems exhibited excellent solubility, with 5 wt% loading elevating CO2 viscosity to 3.68 mPa·s. Ultimately, molecular simulations performed in Materials Studio elucidated the mechanistic basis, electrostatic potential (ESP) mapping, cohesive energy density analysis, intermolecular interaction energy, and radial distribution function comparisons. These computational approaches revealed dissolution and thickening mechanisms of polymeric thickeners in CO2.