Enhanced oil recovery (EOR) operations can provide unique challenges to corrosion prevention. Many of these operations involve injecting CO₂ gas into the well. One more complex approach is a water-alternating-gas (WAG) injection, in which water and gas are alternately injected into the well. This type of process requires that the equipment is able to handle corrosion issues from both water and gas. In these cases, it is normal practice to bring the water and gas in from separate flow lines which enable these lines to be designed specifically for the medium they are carrying, however the wellhead, tubing and casing must be able to withstand both gas and water.