Steam injection lowers the viscosity of heavy oil and oil sands trapped in underground formations. Steam injection is one of the most reliable thermal-enhanced oil recovery methods for heat introduction. Conventional steam applications generate steam from an inefficient high-pressure boiler, which has significant heat losses, degradation in steam quality, and uncertainty in steam distribution in the reservoir while emitting greenhouse gas emissions into the environment. In contrast to the high-pressure steam boiler, a downhole steam generator provides a step-change improvement with immense potential to produce heavy oil below 2500 ft., which can be a transformative thermal-enhanced oil recovery method and pave the way for an exciting advancement.