1. n. [Enhanced Oil Recovery]

A laboratory test in which a fluid or combination of fluids is injected into a sample of rock. Objectives include measurement of permeability, relative permeability, saturation change, formation damage caused by the fluid injection, or interactions between the fluid and the rock. The core material often comes from an oil reservoir, but some tests use outcrop rock. The fluid in place at the start of the test is typically either a simulated formation brine, oil (either crude oil or refined oil), or a combination of brine and oil. Injected fluids may include crude oil, simulated reservoir brine, refined fluids, drilling mud filtrate, acids, foam or other chemicals used in the oil field. Depending on the purpose of the test, conditions may be either ambient temperature and low confining pressure or high temperature and pressure of a subject reservoir. Pressures and flow rates at both ends of the core are measured, and the core can also be investigated using other measurements such as nuclear magnetic resonance (NMR) during the test. A coreflood is typically used to determine the optimum development option for an oil reservoir and often helps evaluate the effect of injecting fluids specially designed to improve or enhance oil recovery.