Steam-assisted gravity drainage (SAGD) is an oil extraction method used primarily for heavy oil and bitumen deposits. In this process, steam is injected into the reservoir to heat the thick oil, reducing its viscosity. This allows the oil to flow more easily to the production wells. Once the oil is heated, it flows by gravity to the lower well, where it is pumped to the surface. SAGD is considered more environmentally friendly than traditional methods, as it requires less land disturbance and reduces greenhouse gas emissions compared to other extraction techniques.