Cyclical steam soak (CSS)

CSS (also known as huff 'n' puff) is a thermal method of heavy oil production. Steam is initially injected into the reservoir and then left to soak by shutting in the well for a number of days. This allows the heat to distribute through the heavy oil and reduce its viscosity. After this period the well is re-started and the oil produced. This process is repeated multiple times until it is no longer profitable.