An Experimental Study for Enhancing the Recovery Factor of Tar Barrier Heterogeneous Reservoirs
Alfayfi, Abdullah . 2015
Abstract
A number of major oil fields in the Arabian Gulf Region include tar barriers between oil and water zones. Such
tar barriers partially or severely impede production as they resist fluid flow in the reservoir. Understanding tar
distribution is therefore, essential for the prediction of reservoir performance under various developmental scenarios
as in water flooding for secondary recovery. The objective of this study is to find out through experimental work the
appropriate techniques for improving the recovery factor of different simulated tar quality that exists in the region.
This investigation was carried out using different laboratory models with a view of selecting the appropriate one
for the region. Consequently, improving tar mobility is one of our major objectives in this study. However, reservoir
heterogeneity together with capillary pressure and dip angle would certainly affect such a process significantly.
Core samples taken from Sarah sandstone formation outcrops in Al-Qassim area of Saudi Arabia were selected
for laboratory experiments which represent heterogeneous sandstone reservoir rocks. The petrophysical properties
of these sandstone rocks were thoroughly investigated by studying properties such as permeability, porosity, relative
permeability, recovery factor, grain size distribution and pore size distribution. Displacement runs were conducted
in 4 in. and 1.5 in. diameter Al-Qassim sandstone outcrops composite cores, simulating tar and crude oil zones
in series, at a constant injection rate of 2 ml/min. These experimental runs were conducted at simulated reservoir
conditions of 60°C, 3500 psi confining pressure and 1500 psi back pressure.
Experimental results show that, the recovery factor was reduced by 26% approximately with tar present in the
system. It increased by 9.2% approximately when the water flooding temperature was increased from 60°C to 90°C
with tar. The recovery factor further increased to around 19% when a combination of hot water and solvent were
used with tar
