Figure 5. Secondary recovery is used in most oil fields to enhance production. Water is injected commonly and is used in Saudi Arabian fields, while steam shown here is used too. The steam plants, shown in the distance venting steam, pump steam into the oil-bearing strata and force the oil to other wells nearby where it is extracted. The technique works on heavy crude and fields that are somewhat depleted. See Heavy Oil. J.H. Lipps image, 1960.