Improving heavy oil recovery using surfactant-assisted waterflooding: Brazilian offshore field

Waterflooding is a widely employed secondary recovery technique in the oil industry. However, in the context of heavy oil reservoirs, its effectiveness is often limited due to the high viscosity and poor mobility of heavy crude. This paper explores the application of surfactant-assisted waterflooding for enhancing oil recovery in heavy oil fields, specifically a shallow-water field located in Campos Basin, Brazil. The heavy oil produced in this field has a viscosity ranging from 500 cp to 800 cp at reservoir temperature of 60 oC.
Surfactant selection and optimization based on reservoir-specific conditions, using reservoir crude oil, and outcrop sandstone cores that closely resembles the reservoir's permeability and mineralogy. Three selected formulations composed of anionic, amphoteric, and anionic/amphoteric mixture were tested in this study. The column drainage test was performed to evaluate the effectiveness of the tested products on enhancing oil mobility in a water saturated sand pack while the coreflood tests were performed to examine the effectiveness of surfactants in terms of heavy oil recovery.
One of the strongest wetting formulations with anionic nature resulted in additional recovery of 13% original oil place (OOIP) in secondary mode over waterflood base case. In addition, this formulation demonstrated a faster oil breakthrough with minimal pressure drop profile. It is noteworthy that other formulations demonstrating lower interfacial tension (IFT) values did not perform as effectively as this engineered anionic formulation. This suggests that wettability alteration could be one of the most influential mechanisms for enhancing heavy oil recovery.

In this study, the strong water-wetting formulation with anionic nature has shown promising results, despite not having the lowest IFT among the tested formulations. This low-dose surfactant-augmented waterflooding technique can be a very favorable alternative for heavy oil recovery compared to other costly methods, such as the steam-assisted gravity drainage (SAGD) and solvent-assisted EOR method.