[[file:enhanced-oil-recovery_fig4.png|300px|thumb|{{figure number|4}}Schematic diagram of ''in situ'' combustion. The mobility of oil is increased by reduced viscosity caused by heat and solution of combustion gases. © U.S. Department of Energy, Bartlesville, Oklahoma.]] | [[file:enhanced-oil-recovery_fig4.png|300px|thumb|{{figure number|4}}Schematic diagram of ''in situ'' combustion. The mobility of oil is increased by reduced viscosity caused by heat and solution of combustion gases. © U.S. Department of Energy, Bartlesville, Oklahoma.]] |