In Situ Combustion is a method used to extract oil from underground reservoirs. This technique involves igniting a portion of the oil in place, which generates heat. The heat helps to reduce the viscosity of the remaining oil, making it easier to flow towards production wells. The process typically starts with drilling wells into the oil reservoir. Air or oxygen is injected to sustain the combustion, while the heat produced helps to mobilize the oil. This method can enhance oil recovery and is often used in heavy oil fields where traditional extraction methods are less effective.