Current appraisal of field miscible slug projects

In miscible slug flooding, a solvent slug is formed in the reservoir either by LPG or rich gas injection. This solvent slug miscibly displaces the reservoir oil ahead of it and is itself moved through the reservoir by the injection of a scavenging fluid. Many facets of this process have been investigated by experimental and mathematical studies. In addition, over 70 field tests of miscible slug flooding have been initiated. These range from early projects initiated originally as LPG disposal operations to more recent completely engineering projects. The available information from these tests is summarized. Process improvements such as pre-solvent water injection and gas-water injection behind the miscible slug are discussed in terms of their advantages and limitations. Their application to several recent large-scale miscible projects is described. In addition, the performance of miscible slug floods in previously water-flooded reservoirs is reviewed and discussed. (45 refs.)