Essentials of Polymer Flooding Technique

Chapter two Chemical Enhanced Oil Recovery Methods

In this chapter, the main chemical methods aimed at improving oil recovery will be described: polymer, surfactant‐polymer, and alkali‐surfactant‐polymer flooding (P, SP, and ASP); microgels; and other conformance methods. A special focus will be placed on ASP flooding, with a brief knowledge summary including some field cases.

2.1. Introduction

Chemical methods utilize a chemical formulation dissolved in fresh water or brine as the displacing fluid, which promotes a decrease in mobility ratio and/or an increase in the capillary number (definitions given in the following paragraphs). The change in mobility ratio is accomplished by adding water‐soluble polyacrylamide to the injection water to increase its viscosity and improve the sweep efficiency inside the reservoir. Changing the capillary number is also possible by adding surface active agents (surfactants), which will decrease the interfacial tension and mobilize residual oil trapped in the reservoir. The addition of alkali promotes wettability changes, generates in situ surfactants (by saponification), and allows for decreasing surfactant concentration when considering ASP. These concepts will be discussed in more detail in this chapter.

Mobilization of oil is the key mechanism for any recovery process, with the saturation distribution of each fluid governed by ...