Abstract
Oil reservoirs are sometimes underlain by thick tar mat layers at the oil-water contact. Such tar mats are found in many major oil reservoirs in the world and, particularly, in the Middle East. Tar mats create several problems in the extraction process during the recovery stages. This study is aimed at investigating the effectiveness of chemical (solvents) method on enhancing the crude recovery from such reservoirs. This study was carried out using different samples of heterogeneous rocks closer in description to those of the real ones in the region. The implications of tar mat layers on oil recovery were examined with different flooding scenarios including water flooding and a combination of water with different solvents. All experimental runs were conducted at 3500psi overburden pressure, 1500psi pore pressure, and 60 degrees C temperature conditions. Results show that the recovery was reduced by 27.34% and 24.9% with tar present in the system for the samples used. The recovery increased by around 6.86% and 7.0% when a combination of water and toluene were used with tar present. Also, the recovery increased by around 2.67% and 2.21% when a combination of water and chloroform were used.