A modified analytical model for field application of improved waterflooding through brine concentration is presented. Based on several laboratory studies, many researchers suggested changing the brine concentration during waterflooding offered viable options for improved oil recovery. In this regard, particularly in cyclic waterflooding, several laboratory studies have confirmed the effectiveness of such approach. However, generally, these studies are limited to laboratory studies without much field application. This is based on the fact that most laboratory results did not present clearly defined approach for practical application. This paper analyses the laboratory results presented in the literature and proffers a concise approach for field application. To this end, based on the reinterpretation of the Civan and Knapp model, a modified oil recovery model is developed for field application during cyclic waterflooding. This model would help in monitoring waterflood performance based on the impact of brine injection on increased oil recovery during field application of cyclic waterflooding process.
The process of improving waterflooding performance through brine concentration has obvious practical benefits. Several laboratory studies have indicated increase in oil recovery with change in injected brine salinity. Crude oil properties, particularly the solvency of high molecularweight polar component and modest increase in temperature have been shown to have a major effect on crude oil, brine and rock interacti that selection or adjustment of an injection brine composition to advantageously alter wettability is a novel method for increasing oil recovery at potentially low cost. They demonstrated that laboratory waterflood recoveries of crude-oil/brine/rock (COBR) ensembles are strongly dependent on brine composition and on related COBR interactions. To this end, it was shown that rate and extent of final waterflood recoveries increased with decrease in brine concentration.
Tang and Morrow (1999) reported that modification to brine chemistry have resulted not only in changes in the wetting state, but also increasing oil recovery during laboratory corefloods. Another study (4) suggested a significant increase in recovery with decrease in salinity and presented laboratory results on oil recovery from a selected field for potential application. In addition to improved oil recovery, COBR combinations were also found where there was little or no response to injected brine composition. Bagci et al. (2001) studied the effect of brine composition on oil recovery through injection of different composition of brine into packed one-dimensional unconsolidated limestone core using Garzan crude oil and distilled water. They reported only slight response for the limestone core sample used, which confirmed findings that laboratory evaluations are essential to identifying potential candidate reservoirs for application(4).
Laboratory testing has identified three key conditions for the waterflooding process to be effective through controlled.
