A Laboratory Workflow to Screen Fracturing Fluid Additives for Enhanced Oil Recovery
Creators: Eghbalvala, Maryam
Publisher: name: University of Alberta Library
Year: 2023

<p>Increasing demand for oil and gas and rapid depletion of conventional resources have shifted the focus of the industry toward hydrocarbon production from unconventional resources. Due to the extremely low permeability, complex pore structure, and mixed-wet behavior of such formations, their oil recovery factor is very low (&lt;10%) and a considerable amount of hydrocarbon will be trapped in the sub-micron pores. Numerous enhanced oil recovery (EOR) methods have been introduced during the past decade to increase the final oil recovery from these formations. In recent years, many investigations have evaluated the application of surfactants and cosurfactants for enhancing oil recovery. These chemicals are best known for their surface activity for reducing interfacial tension (IFT) between oleic and aqueous phases and wettability alteration of the rock, both affecting capillary pressure (Pc). Water blockage at the hydraulic fracture-matrix interface is considered as formation damage in tight formations with low permeabilities, and this causes reduction of hydrocarbon recovery. Due to very small pore throats in tight formations, capillary suction is high at the interface and causes the injected fluid to enter the matrix and trap, which reduces hydrocarbon mobility. Addition of nanodroplets and surfactants reduces the capillary force which enhances water imbibition through the matrix and reduces formation damage as a result. In this study, we characterized fluid-fluid and rock-fluid properties to investigate parameters affecting oil recovery from tight rocks by the addition of nanoparticle additives to fracturing water and categorized these parameters according to their impact in enhancing oil recovery</p>

<p>This study presents a comprehensive laboratory workflow to investigate different parameters affecting the efficiency of enhancing oil recovery (EOR) from tight rocks using nanoparticle additives. We used core samples from the Montney (MT) Formation and nanodroplet (ND) solutions prepared by three complex nanofluid additives which include nonionic surfactants and D-Limonene solvent to conduct our experiments. This protocol is applied in the following steps: (1) Characterizing natural wettability of the core plugs by spontaneous imbibition and contact angle tests; (2) Evaluating ND-assisted imbibition oil recovery tests by conducting systematic imbibition oil recovery tests under different brine salinities; and (3) Performing bulk-phase tests to evaluate fluid properties, particle size, and stability of the ND samples to understand fluid-fluid interactions.</p>

<p>The experimental results show that the use of nanodroplet additives decreases the oil-water interfacial tension (IFT) and alters the rock wettability towards more water-wet conditions. However, enhanced imbibition oil recovery using ND solutions prepared by CnF additives cannot be sufficiently explained by IFT reduction and macroscopic CA measurements. Solubilization (described by Winsor type), osmosis potential, and zeta potential should also be considered to evaluate imbibition oil recovery by the ND solutions. Generally, increasing fluid salinity can reduce oil recovery by the ND solutions, which can be explained by less fluid movement through the pores, so weaker osmosis potential and the formation of larger particles in high-salinity water. The solubility results of Pipette tests indicate that the formation of middle-phase (or near middle-phase) microemulsion is favorable to increase oil recovery. As the generated microemulsion type gets closer to Winsor type III, the oil-water IFT value reaches the minimum value, which enhances the oil recovery. Measured Zeta potential values reveal that higher absolute value of oil-ND solution maintains a high net negative charge around the oil droplets. This results in higher stability and higher solubility of the oil droplets in the aqueous phase, which leads to higher final oil recovery.</p>