Secondary Recovery

This chapter focuses on secondary recovery techniques, and in particular, on waterflooding. Waterflooding is often applied after the primary recovery phase, when oil has been produced by either the existing pressure within the reservoir or by artificial lift as discussed in Chapter 8. A waterflood acts to improve both the rate and the total amount of oil recovered from an oil field by two main mechanisms – by reducing the rate at which the reservoir pressure falls as oil and water are produced from the reservoir, and by displacing (or pushing) the oil towards the production wells. A properly planned and executed waterflood can recover up to an additional 50% of the oil originally in place, depending upon the nature of the reservoir and its fluids. In a waterflood, water is injected into the target formation through injection wells. The Ekofisk waterflood in the North Sea is studied as an example of a successful application of the technique.