Final answer:
Enhanced Oil Recovery (EOR) is a set of techniques to extract additional oil from depleting fields by improving pressure and flow, increasing extraction beyond primary and secondary methods. The profitability and efficiency of these methods are measured by EROEI, indicating the energy output relative to the energy invested in extraction.
Step-by-step explanation:
Enhanced Oil Recovery (EOR) Defined
Enhanced Oil Recovery (EOR) is a set of techniques used to extract more oil from an oil field than would be possible with primary and secondary oil recovery methods. As oil fields mature and the easily recoverable oil is depleted, EOR techniques are used to increase the pressure within the reservoir, improve the flow characteristics of the oil, and ultimately recover more oil.
Understanding EROEI
The term EROEI stands for Energy Returned on Energy Invested, which is an important concept when evaluating EOR. Essentially, EROEI is a measure of how much energy is gained from an energy-producing process compared to the energy invested in that process. For instance, if an operation produces a high EROEI, it indicates a higher amount of energy is being extracted than the energy used to extract it, making it a more profitable and effective operation.
For example, an EROEI of 100:1 means that for every unit of energy input, 100 units of energy are produced, which is highly desirable. Conversely, as we access more difficult oil resources, the EROEI tends to decrease. Some unconventional sources like tar sands may have an EROEI as low as 3:1, indicating that for every unit of energy put into the extraction process, only three units are obtained, thus requiring more energy investment for less energy return.