Diffusion of CO₂ in single-step silica nanofluid for subsurface utilization: an experimental study

Area of Science:

• Materials Science
• Chemical Engineering
• Petroleum Engineering

Background:

• Enhanced oil recovery and carbon capture technologies require efficient methods for carbon dioxide (CO2) absorption.
• Nanofluids offer potential as advanced additives to improve fluid properties in subsurface applications.
• Silica-based nanofluids are being explored for their unique characteristics in various industrial processes.

Purpose of the Study:

• To investigate the efficacy of single-step silica nanofluids as additives for enhancing CO2 absorption in polymeric solutions.
• To evaluate the performance of these nanofluids under high pressure-high temperature (HPHT) conditions relevant to oilfield applications.
• To optimize nanofluid parameters, including nanoparticle size and concentration, for subsurface CO2 carrier fluid applications.

Main Methods:

• Utilized a pressure decay approach within a high pressure-high temperature (HPHT) cell to measure CO2 absorption.
• Tested silica nanofluids with varying nanoparticle sizes (30-120 nm) and concentrations (0.1-1 wt%).
• Conducted experiments across a pressure range of 5-10 MPa and temperatures of 30-90 °C, simulating near-reservoir conditions.

Main Results:

• Increased nanoparticle concentration (0.1-1 wt%) significantly enhanced CO2 absorption, indicated by a sharper pressure decline.
• Larger nanoparticle size (30-120 nm) reduced CO2 absorption capacity.
• Elevated temperatures (30-90 °C) decreased CO2 absorption by 12-19%, while pressures above 7.5 MPa were detrimental due to CO2's supercritical nature.
• Sodium chloride (NaCl) addition reduced absorption by up to 33%, whereas sodium dodecyl sulfate (SDS) slightly increased it in saline conditions.

Conclusions:

• Single-step silica nanofluids demonstrate significant potential as CO2 carrier fluids in oilfield applications.
• Optimal CO2 absorption is achieved with smaller silica nanoparticles and lower concentrations.
• The application of these nanofluids is recommended for oilfield conditions with salinity below 4 wt%.