Application of Enhanced Oil Recovery Methods in Unconventional Reservoirs: A Review and Data Analysis

Production from unconventional reservoirs using enhanced oil recovery (EOR) has gained much attention in recent years due to its ability to dramatically increase oil recovery. This paper reviews all EOR methods which have been applied in unconventional reservoirs, with the aim of constructing a roadmap for the conditions at which different EOR methods are applicable. The most applicable unconventional techniques that have been reported to enhance oil recovery are Carbon Dioxide (CO2) gas injection, low salinity water flooding, and surfactant. Various tools are employed to study EOR methods in unconventional reservoirs including simulation, experimental, and field cases. Most of the reviewed studies utilize simulation and experimental tools. Notably, we discovered that gaseous EOR methods, such as huff-n-puff gas injection, were widely used to investigate the applicability of such methods. The most widely used gas that was reportedly used is CO2. Of the chemical methods, surfactant is the material with the most potential to improve oil recovery due to its ability to change the wettability of the reservoir rocks to water wet. We present an analysis of the most common fluid and rock properties of unconventional reservoirs