Secondary recovery is a method used in the oil and gas industry to extract additional hydrocarbons from a reservoir after primary recovery techniques have been exhausted. Primary recovery typically relies on natural pressure and pumping, which can only extract about 10-20% of the oil. Secondary recovery techniques, such as water flooding or gas injection, help to maintain reservoir pressure and push more oil towards production wells. These methods enhance the extraction process by introducing fluids into the reservoir, which displaces the oil and makes it easier to extract. Water flooding involves injecting water into the reservoir, while gas injection uses gases like carbon dioxide to increase pressure. Together, these techniques can significantly improve the overall recovery rate of oil and gas resources.