Experimental Investigation of Synthetic Fines Injection for Enhanced Residual CO2 Trapping during CO2 sequestration

This thesis presents an idea to enhancing residual CO2 trapping by injecting particles carried by the injected CO2. Natural fines migration can enhance residual CO₂ trapping through pore-throat blockage; however, this mechanism is mainly limited to clay-bearing sandstones containing mobile fines generated in situ. In sandstones with limited or no natural fines, this trapping mechanism may be ineffective. Therefore, synthetic fine particle injection offers a controllable approach to overcome this limitation and enhance residual CO2 saturation as a result of residual CO₂ trapping. First, wettability characterization of the rock is made. Characterization techniques, including scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), are performed before and after the experiment to analyse surface changes associated with CO₂–water interaction. X-ray photoelectron spectroscopy (XPS) analysis was performed at the sessile droplet location after the experiment, for analysis of surface chemistry. Contact angle measurements on Berea sandstone was performed for any difference between captive bubble and sessile drop method. A high-pressure, high-temperature (HPHT) visual cell is used for contact angle measurements, at 50 C° and 1450-2100 psi. For, Particle injection, drainage and imbibition experiments are performed using water-saturated CO2, and CO2-saturated water on sandstone cores. The cores receive three injection stages: water, water-saturated CO2, and finally CO2-saturated water on two different types of sandstone core samples: (i) Berea, and (ii) Bentheimer. Two different types of particles are injected:(i) non-porous and (ii) porous silica particles. The particle was introduced into the CO2 phase based on initial state: (i) dry powder, (ii) aqueous dispersion. To investigate impact of particle size variation on residual CO2 saturation particle size sensitivity is performed using both non-porous and porous particle, in dry powder form on Berea sandstone core. The pressure difference across the core samples was recorded during injection experiments, and permeability drop measured as permeability ratio before and after each injection experiment. Results indicate captive bubble contact angle measurements is consistent between 23° and 31° while sessile drop is between 38° and 113°. The hysteresis might be attributed to the difference in the ways CO2-water-rock interacts in the two methods. During Captive bubble measurements, Fe2+ was desorbed from whole sample while Na+, Cl-, ions appeared with no crystallization. In sessile drop the oxidation of iron was detected at droplet location, along with appearance of other ions such as Mg2+, Ca2+. The drying-out of the sessile drop led to NaCl crystallization at droplet location. The CO2-water-rock interactions in the two methods yielded different surface chemistry and roughness. In particle injection experiments the measured pressure difference fluctuated more severely when particles were injected, indicating blockage within the core samples. For Berea, residual CO2 saturation increased by 4-5% as a result of residual CO2 trapping regardless of the type of particles used. For Bentheimer, no improvement in residual CO2 saturation was observed when the initial state of the particles was dry. However, when the initial state of particle was aqueous dispersion, residual CO2 saturation increased by 2% only. This was attributed to particle aggregation, and low jamming ratio. Berea sandstone permeability drop was 9-13 % compared to 3-4% in Bentheimer. Particle size sensitivity found to have an optimum particle size for each type of particles after which the improvement in residual CO2 saturation is start to reduce. Residual CO₂ saturation increased with particle size up to an optimum value, before declining at larger particle sizes. For non-porous particles, no further increase in residual CO₂ saturation was observed for particle sizes larger than 50 nm, whereas for porous particles, this decline occurred for sizes larger than 30 nm. For both types of particles, the maximum residual CO2 saturation attained was 5 % as a result of residual CO2 trapping.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2026

Author dc:creator

• Mansoor, Rehan

• CO2 Sequestration
• Residual CO2 Trapping
• Particle injection
• Enhanced CO2 Trapping
• anzsrc-for: 410101 Carbon sequestration science
• anzsrc-for: 401907 Petroleum and reservoir engineering

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/32352

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/107929