Reservatórios de petróleo

Formation Evaluation MSc Course Notes

Reservoir Drives

Chapter 3: Reservoir Drives
3.1 Introduction
Recovery of hydrocarbons from an oil reservoir is commonly recognised to occur in several recovery stages. These are: (i) (ii) (iii) (iv) Primary recovery Secondary recovery Tertiary recovery (Enhanced Oil Recovery, EOR) Infill recovery

Primary recovery This is the recovery of hydrocarbons from the reservoir using the natural energy of the reservoir as a drive. Secondary recovery This is recovery aided or driven by the injection of water or gas from the surface. Tertiary recovery (EOR) There are a range of techniques broadly labelled ‘Enhanced Oil Recovery’ that are applied to reservoirs in order to improve flagging production. Infill recovery Is carried out when recovery from the previous three phases have been completed. It involves drilling cheap production holes between existing boreholes to ensure that the whole reservoir has been fully depleted of its oil. This chapter discusses primary, secondary and EOR drive mechanisms and techniques.

3.2 Primary Recovery Drive Mechanisms
During primary recovery the natural energy of the reservoir is used to transport hydrocarbons towards and out of the production wells. There are several different energy sources, and each gives rise to a drive mechanism. Early in the history of a reservoir the drive mechanism will not be known. It is determined by analysis of production data (reservoir pressure and fluid production ratios). The earliest possible determination of the drive mechanism is a primary goal in the early life of the reservoir, as its knowledge can greatly improve the management and recovery of reserves from the reservoir in its middle and later life. There are five important drive mechanisms (or combinations). These are: (i) (ii) (iii) (iv) (v) Solution gas drive Gas cap drive Water drive Gravity drainage Combination or mixed drive

Table 3.1 shows the recovery ranges for each individual drive