Enhanced Oil Recovery

Nearly 2.0 × 1012 barrels (0.3 × 1012 m3) of conventional oil and 5.0 × 1012 barrels (0.8 × 1012 m3) of heavy oil will remain in reservoirs worldwide after conventional recovery methods have been exhausted. It is important for the O&G industry to recover more hydrocarbons to supply the increasing world energy demand.


To maximize the recovery of hydrocarbons from a reservoir, several methods can be implemented after the natural depletion stage is over. The secondary methods which comprise water or gas injection help in maintaining the reservoir pressure to ensure hydrocarbon flow to the production wells. The recovery factor at the end of this stage often remains below 40% of the Oil Originally in Place. Tertiary methods are then developed to overcome this issue and reach recovery factors above 60%.


Polymer flooding belongs to chemical enhanced recovery; it is a well-known method (over 40 years of commercial application) with low risk and application over a wide range of reservoir conditions. It consists in dissolving polymer in the injected water to increase its viscosity and to improve the sweep efficiency in the hydrocarbon reservoir.


A typical polymer flood project involves mixing and injecting polymer over an extended period of time until at least 30% of the reservoir pore volume has been injected. This polymer “slug” is then followed by continued long-term waterflooding to drive the polymer slug and the oil bank in front of it toward the production wells.


Surfactants can be combined with polymer (SP for Surfactant Polymer) to mobilize the trapped oil by changing the Interfacial Tension between Oil and Water.


The addition of Alkali to the Surfactant Polymer System (ASP) generates in-situ surfactants and can alter the wettability of the rock, mobilizing more oil.