Effect of Silica Nanofluid on Nanoscopic Pore Structure of Low-Permeability Petroleum Reservoir by Nitrogen Adsorption Technique: A Case Study

Abstract

Silica nanofluids have proven to be successful in improving hydrocarbon recovery in the petroleum industry, and increased demand for hydrocarbons has necessitated its application in low-permeability reservoirs. In recent times, surface coating of nanoparticles has been employed to reduce its retention in porous media, but this does not entirely eliminate nanoparticle attachment to pore walls. Knowledge of changes that occur in pore wall and structure such as specific surface area (SSA), pore size distribution and total pore volume (TPV) would be useful in understanding retention mechanisms. This study used nitrogen adsorption technique in studying changes in pore structure due to silica nanofluid treatment. The Brunauer–Emmett–Teller theory and Barrett–Joyner–Halenda adsorption model were used in determining SSAs and TPVs, respectively. SSA, adsorbability and TPV increased in treated samples compared to untreated samples and the rates of change increased with treatment time due to extra pores induced by nanoparticle coagulation. Percent changes in TPV matched closely with SSA and was responsible for increments in the latter. Scanning electron micrographs confirmed coagulation of nanoparticles which increased with treatment time and introduced pseudo-pores on pore walls, resulting in increase in TPV. Increase in differential pore volume was observed for the entire studied range of 2–100 nm except for 3–4 nm which showed no changes in all samples. Severity of differential pore volume increased with treatment time. This study provides insights into nanoscopic changes that occur on pore walls and structure when employing silica nanoparticles in improving hydrocarbon recovery in low-permeability hydrocarbon reservoirs.