Evaluation of combined low-salinity water and microgel treatments to improve oil recovery using partial fractured carbonate models

Abstract

Combining two methods in one process to enhance oil recovery represents a needed cost savings in the oil industry. Microgels are used as conformance control agents to improve oil sweep efficiency and control excess water production. Low-salinity waterflooding (LSWF) is used as a wettability alteration agent in carbonate reservoirs and improves displacement efficiency. This paper offers a comprehensive understanding of the combined technology through laboratory experiments. The focus of this study is to see how microgels and low water salinity perform in porous media by creating flow resistance to injected fluid thereby changing the wettability and enhancing the sweep and displacement efficiency. This study elucidates the influence of swelling ratio, fracture width, microgel-placed pressure, and wettability on the oil recovery factor and water residual resistance factor (Frrw). A set of carbonate cores from Indiana Limestone was used to evaluate the performance of the combined method in partially open fractures. The model was constructed of two acrylic plates, and microgels and brine movements were visible through a transparent side of the model. Result shows that oil recovery factor increases with swelling ratio and microgel placed pressure but decreases with the increase of fracture width. It was shown that oil recovery improved by 10% when the swelling ratio increased from 40% to 160% and improved by 9% when fracture width decreased from 0.8 cm to 0.2 cm. Also, the combined method shows larger effect in the oil-wet core when compared to the water-wet core. Frrw increases with the increase in swelling ratio and microgel-placed pressure but decreases with the increase of fracture width.