Oil recovery operations traditionally have been subdivided into three stages. What are the three stages?

Oil recovery operations traditionally have been subdivided into three stages. What are the three stages?

• A. Primary, secondary, and tertiary recovery
• B. Primary, tertiary, and secondary recovery
• C. Secondary, primary, and tertiary recovery
• D. Primary only

Answer: (A)

Oil recovery is described in stages based on how energy is used to bring oil to the surface over the life of a field. The first stage relies on the reservoir’s own natural drive and formation energy to push oil toward the wells. As this natural pressure wanes, the second stage uses external energy sources, such as injecting water or gas, to maintain pressure and displace more oil toward the wells. After those methods, the third stage involves enhanced techniques—like steam heating, chemical flooding, or miscible gas injection—to improve sweep efficiency and recover additional oil that previous stages couldn’t reach. Thus, the traditional sequence is primary, secondary, and tertiary recovery. The other options either omit a stage or misorder them, which doesn’t reflect how oil recovery progresses over a field’s life.

Oil recovery is described in stages based on how energy is used to bring oil to the surface over the life of a field. The first stage relies on the reservoir’s own natural drive and formation energy to push oil toward the wells. As this natural pressure wanes, the second stage uses external energy sources, such as injecting water or gas, to maintain pressure and displace more oil toward the wells. After those methods, the third stage involves enhanced techniques—like steam heating, chemical flooding, or miscible gas injection—to improve sweep efficiency and recover additional oil that previous stages couldn’t reach. Thus, the traditional sequence is primary, secondary, and tertiary recovery. The other options either omit a stage or misorder them, which doesn’t reflect how oil recovery progresses over a field’s life.