Abstract: Oil is recovered from underground reservoirs using hydrocarbons produced from cracking equipment located near the site. The equipment is operated at pressures proximate existing underground formation pressure to produce hydrocarbons for direct injection into the formation with reduced or no further compression. The hydrocarbons are injected at selected locations in the reservoir to pressurize the field, effectively reduce the oil viscosity and cause its flow into production wells. Specialized field cracking equipment, such as units for simple, small scale, low fouling operation that circulate heavy coke slurries, may be used to produce the hydrocarbons for injection.