Experimental investigation of innovative superheated vapor extraction technique in heavy oil reservoirs: A two-dimensional visual analysis

Abstract

Steam-assisted gravity drainage (SAGD) has been widely employed for heavy oil exploration, which however suffers low oil displacement efficiency and high-water consumption. Conventional vapor extraction (VAPEX) remediates those issues, nevertheless, accompanied by low oil production rate with cold or warm solvents injection. Here, an innovative thermal VAPEX was investigated for when injecting superheated solvents (>160OC). The thermal properties of several solvents were compared to indicate the impacts of temperature and solvent concentration. Three sets of two-dimensional visualization experiments were conducted to elucidate the changes of temperature field and solvent chamber, characterized by oil recovery, cumulative oil exchange rate and solvent retention. The results showed that a hot solvent with a higher carbon number resulted in a larger latent heat of vaporization and a better viscosity reduction effect by dissolution and heating. The viscosity reduction rate of n-pentane (below 10 wt%) was approximately 70%. Solvent chamber developed step-wisely: rising stage, lateral expansion stage and descending stage. Over liquid solvent, solvent vapor rendered greater sweep efficiency (75%), displacement efficiency (85%), much lower solvent retention (10%), high oil recovery (65%), and cumulative oil exchange rate (8 t/t). Current studies provided a reliable experimental basis to further exploit thermal vapor on site.