Thermal recovery is a method used in the oil and gas industry to extract crude oil from underground reservoirs. This technique involves injecting heat, often in the form of steam, into the reservoir to reduce the viscosity of the oil, making it easier to flow to the surface. There are different types of thermal recovery methods, including steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS). These methods are particularly effective in heavy oil fields, where traditional extraction techniques may not be sufficient to recover the oil efficiently.