Thermal Recovery

(or thermal drive), methods of exploiting petroleum deposits by using the effect of heat on oil-bearing formations. The main principles for the development of thermal recovery were set forth by D. I. Mendeleev in 1888, D. V. Golubiatnikov in 1916, I. M. Gubkin in 1928, and A. B. Sheinman and K. K. Dubrova in 1934. Thermal recovery was introduced in the USSR in the 1930’s.

Electric power, combustion, steam, and hot water are used for heating oil beds during thermal recovery. The thermal recovery methods that are of the greatest practical importance are in-place combustion, fireflooding, injection of heat carriers, electrothermal or thermochemical well treatment, and steam drive. In-place combustion or fireflooding is accomplished by burning about 10 percent of the residual oil in the formation. The combustion wave, which is initiated by various subsurface heating devices using electricity, fire, or chemical reactions, moves through the formation as air is supplied. This produces an increase in formation temperature to the order of 400°–500°C. Oil is displaced from the formation by gases, such as nitrogen, carbon dioxide, or steam, or by the evaporation of light fractions, which are then moved in the direction of the drive. Fireflooding is performed by injecting water into the formation together with an oxidizing agent, thus accelerating the processes of heat transfer and oil extraction. In processes using the injection of heat carriers, the heat carrier (steam or preheated water) is prepared on the surface with the use of steam generators and water heaters. Because of increased heat losses at greater depths, heat-carrier injection is usually used in deposits lying no deeper than 600–800 m. After in-place combustion, fireflooding, or injection of heat carriers has been used in part of the formation, a shift is made to conventional waterflooding to provide greater economy. The heated zone, however, is still driven through the formation.

In the electrothermal, thermochemical, and steam-stimulation processes, a temperature favorable for oil inflow and well recovery through improvement of effective permeability or dissolution of paraffin-asphaltene-resinous deposits in the petroleum is produced and maintained in the bottom-hole area. The wells, at 80°–150°C, are treated periodically or continuously by means of surface or subsurface heat generators.

Thermal recovery increases the recovery factor by 10–25 percent, improves the flow of oil from the formation, and makes possible the exploitation of deposits of viscous, asphaltic paraffincontaining resinous petroleum, the control of thermal conditions in the reservoir, and the provision of cooling relief for the formations. It also reduces the time needed to develop deposits.