Laboratory Investigation of Low Salinity Waterflooding as Secondary Recovery Process: Effect of Wettability

Abstract

Laboratory studies along with field tests conducted over the decade reveal that reducing the salinity of water injected into reservoirs improves the oil recovery. Different phenomena e.g. increase in pH (alkalinity), fines migration, multi-component ionic exchange, etc., have been proposed by researchers for improved oil recovery during low salinity waterflooding (LSW). Though LSW has attracted attention among reservoir engineers as tertiary recovery process, limited studies have reported the potential of LSW as secondary recovery process. Also, the relationship between reservoir rock parameters such as wettability, rock minerals, etc. and oil recovery is not well established for LSW. The objective of this paper was to investigate the relationship between rock wettability and oil recovery with low salinity water injection as secondary recovery process. Coreflooding experiments have been performed at room conditions on Berea cores with four different wettabilities ranging from water- to oil- wet. Brines and n-decane were used as displacing and displaced phases, respectively. The results showed that, for all the salinities, oil recovery increases as wettability changes from water- to neutral- wet conditions. Further change in rock wettability from neutral- to oil-wet condition resulted in decreased oil recovery. It was also interesting to observe that oil recovery is higher for LSW as compared to high salinity waterflooding when used as secondary recovery process. Increase in pressure drop and hence decrease in effective permeability was also observed during LSW process in most of the cases considered.

Application of nanofluid to control fines migration to improve the performance of low salinity water flooding and alkaline flooding

“…Low-salinity water (LSW) flooding has been widely documented as a promising improved oil recovery technique in literature (Ashraf et al, 2010;Morrow and Buckley, 2011;Morrow, 1997, 1999). In this process, the brine chemistry has been recognized as an important parameter critically affecting the efficiency of the process.…”

“…In this process, the brine chemistry has been recognized as an important parameter critically affecting the efficiency of the process. Different laboratory and field studies have proved the remarkable low salinity effect on the ultimate oil recovery and reported greater oil recovery with decreasing the ionic strength of water (Ashraf et al, 2010;Hassenkam et al, 2012). On the other hand, the brine chemistry drastically affects the interactions of colloidal particles, situated on the pore walls, with the medium surface (Lager et al, 2008;Nasralla et al, 2011).…”

Modeling of Ion-Exchange and Solubility in Low Salinity Water flooding

“…Fogden and Lebedeva (2011) found out that there was increased oil particles deposited on kaolinite surfaces in low salinity environment than in high salinity water environment. Ashraf et al (2010) carried out secondary corefloods with oil having different wetting tendencies and reported that low salinity water improved recovery under oil wet, water wet and neutral wet conditions, with the water wet conditions showing the biggest low salinity water effect. Positive low salinity effect was also seen in tertiary corefloods using both predominantly basic oil and a predominantly acidic oil .…”

Low Salinity as New Technique of Enhanced Oil Recovery

“…Some researchers reported that low salinity water flooding change the wettability into neutral state rather than water-wet state [8], [9]. Ashraf et al [4] pointed out same result.…”

“…The performance of a water flooding is typically affected by the following main parameters: reservoir geology and geometry, physical properties, porosity, permeability, heterogeneity, fluid properties: viscosity, mobility ratio, mineralogical properties: clay type and amount. Over decades much research has been done to optimize these parameters to be able improve water flooding process [4]. The effect of water chemistry on brine-rock interactions was seldom paid any attention, even though the effect of low salinity brine in sandstone rock containing clay was revealed in the 60's.…”