Low Interfacial Tension Foam Miscible Ethane Oil Recovery in Low Permeability Harsh Environments
This work presents a laboratory investigation of low interfacial tension miscible ethane foam enhanced oil recovery in low permeability, heterogeneous, harsh environments (<15md, 136,000ppm total dissolved solids with divalent ions, 74°C). Minimum miscibility pressure displacement tests were performed for dead crude oil from the Wolfcamp Spraberry trend area using ethane and carbon dioxide, showing a lower MMP for ethane. A surfactant formulation capable of persistent foams in the presence of oil and Type I microemulsion in reservoir brine was identified to be thermally stable at reservoir conditions. Subsequent foam quality and coreflood displacement tests were conducted to compare the recovery efficiencies of three processes: a) gravity–unstable, miscible ethane foam; b) gravity–stable, miscible ethane, and; c) gravity–unstable, miscible ethane processes.