Smart Water injection into sandstone reservoirs for enhanced oil recovery - Influence of oil components on sandstone wetting

Abstract

Both fluid flow and Smart Water EOR process in reservoirs are affected by the reservoir wetting. In order to study the wettability effect of polar organic components present in crude oil, the adsorption of acidic and basic polar components onto mineral surfaces have been investigated. 2 outcrop sandstone cores, B-15 and C-3, were flooded with crude oil and produced effluent oil was sampled and analysed for AN and BN.

Both core B-15 and C-3 had an initial water saturation of 20% and flooded with FW with a salinity of 50 000 ppm and added a small amount AlCl3 to reduce the initial pH conditions in the cores. Thereafter the cores went through a crude oil flooding with AN=0.2 and BN=0.31 and 0.22 respectively. The temperature during both experiments were 50°C.

The experimental observation shows that the adsorption of basic components was instantaneous and the cores became mixed-wet, confirmed through spontaneous experiments with FW as imbibing brine. FW brine pH could be supressed by adding small amounts of Al3+ ions to the FW. The acidic components had far less affinity towards the mineral surface at the initial conditions present in the cores. When switching from FW to LS-brine, increased oil production was observed. Confirming a wettability alteration taking place even for mixed-wet neutral sandstone cores.