Effect of Conformance Control Patterns and Size of the Slug of In Situ Supercritical CO₂ Emulsion on Tertiary Oil Recovery by Supercritical CO₂ Miscible Injection for Carbonate Reservoirs

Abstract

The reservoir heterogeneity is the major cause of poor volumetric sweep efficiency in sandstone and carbonate reservoirs. Displacing fluids (water, chemical solution, gas, and supercritical CO 2 (sc-CO 2 )) flow toward the high permeable zone. A significant fraction of oil remains in the low permeable zone due to the permeability contrast. This study used in situ sc-CO 2 emulsion as a conformance control agent to plug the high permeable zone and improve the low permeable zone's volumetric sweep efficiency in carbonate formation. We investigated the effect of two types of conformance control patterns and the size of sc-CO 2 emulsion on tertiary oil recovery performance by sc-CO 2 miscible injection for carbonate reservoirs at reservoir conditions. The conformance control patterns are achieved using two different approaches. In the first approach, the low permeable zone was isolated, and the diverting gel system, a 0.4 pore volume slug, was injected into a high permeable zone. In the second approach, the simultaneous injection of the diverting gel system, a 0.2 pore volume slug, was done on both the low and high permeable zones. The first sc-CO 2 injection was conducted as a tertiary oil recovery mode to recover the remaining oil after water flooding. The diverting gel system was injected after the first sc-CO 2 flood for the conformance control. The second or post sc-CO 2 injection was conducted after the diverting gel system injection. The diverting gel system used in this study consisted of a polymer and a surfactant. An in situ emulsion was generated when the injected diverting gel system interacts with the sc-CO 2 in the core plug. Results obtained from dual-core core flooding experiments suggested that the in situ sc-CO 2 emulsion was generated successfully in the formation based on the different pressure increases and observation of the dual-core core flooding experiments. The volumetric sweep efficiency and oil recovery in both conformance control patterns were improved. The production performances were also compared for both conformance control models before and after the diverting gel system injection. The conformance control model 2 (simultaneous injection of the diverting gel system into low and high permeability cores) has a better choice to be applied in field application due to high recovery with a small sc-CO2 emulsion easy operation in the field.

Review on Microemulsions for Conformance Improvement Technology: Fundamentals, Design Considerations, and Perspectives

“…For conformance improvement, the solubilization parameter assesses the ability of the emulsifier to exhibit sufficient interfacial characteristics to the microemulsion. 33 This condition is achieved by the formation of highly efficient sheltering structures, such as direct micelles, reverse micelles, and bilayer structures. These structures consist of a core phase encapsulated by the presence of surfactants and dispersed in an otherwise solvent phase.…”

Technical Evaluation of Conformance Improvement Technology with Anionic Surfactant-Stabilized Microemulsions in Porous Media

“…The oil present in the high permeability zones was produced during this water flood and the water cut gradually increased to values as high as ~98%. This represents a state of uneconomical water production ratio and requires chemical intervention to render a 'conforming' drive the porous flow (Ding et al, 2021;X. Zhou et al, 2020).…”

“…The pressure response showed a sharp increase in pressure drop with a favorable reduction in water cut percentage to 30% until 0.84 PV injection of ME fluid. This occurs due to the plugging of water channels in the high permeability zones of the rock, which leads to a lower water-to-oil production ratio (Ding et al, 2021;Irani and Ghannadi, 2020;Sagbana and Abushaikha, 2021;X. Zhou et al, 2020).…”

“…Microemulsion-assisted conformance improvement technology (ME-CIT) is based on the cyclic injection of microemulsion/surfactant slugs in surface conditions and sufficient viscosity within the targeted pore regions (Das et al, 2020;Quintero et al, 2015;. It relies on two important attributes: stability and viscosity (Divandari et al, 2021;Sagbana and Abushaikha, 2021;X. Zhou et al, 2020).…”

Stimuli-Responsive, Hydrolyzable Poly(Vinyl Laurate-co-vinyl Acetate) Nanoparticle Platform for In Situ Release of Surfactants

“…The release mechanism, as illustrated in Scheme , involves slow hydrolysis of the ester group to generate carboxylic acid, which subsequently reacts with the carbonate surface to produce carboxylate salts. In addition to the surfactant generation, during hydrolysis, the generated carboxylic acid assists using the stimulation of carbonate formations and the generated carbon dioxide (CO 2 ) gas promotes conformance control. , The ratio of constituent monomers and the PEG length, which acts as a protective shell, were optimized to achieve colloidal stability, while ensuring a proper hydrolysis rate of the ester side chain. In addition, the hydrolysis kinetics and the surfactant release profile were systematically studied under various salinity and temperature conditions.…”