Efficiency of enhanced oil recovery using polymer-augmented low salinity flooding

Abstract

Oil recovery from heavy oil resources has always been a challenging task. This work is aimed at investigating the recovery efficiency of polymer-augmented low salinity waterflooding in heavy oil reservoirs. The main recovery mechanism behind low salinity waterflooding is wettability alteration to more water-wet state. On the other hand, polymer flooding is performed to control fluids mobility and hence improve displacement efficiency. Combining both recovery methods is expected to add to recovery efficiency obtained by individual methods, and the aim of this work is to explore this experimentally. In this study, several laboratory experiments were conducted using Berea and Bentheimer sandstone cores starting with base runs of continuous secondary seawater and tertiary twice and 10 times diluted seawaterflooding (low salinity). Significant incremental oil recovery was obtained when flooded with low salinity water, and 10 times diluted seawater was determined to be used as low salinity water. Contact angle and Zeta potential measurements indicate wettability alteration due to clay detachment as the main recovery mechanism. Synergy of water secondary flooding and polymer tertiary flooding at different water salinity levels proved the efficiency of hybrid low salinity polymer flooding process in Berea sandstone. Low water salinity during secondary injection mode played a major role on ultimate recovery with less contribution to tertiary polymer slug injection. High salinity waterflooding provided lower secondary recovery leaving more residual oil for polymer slug to act on at that cycle. Smaller polymer slug of 0.1 pore volume was found to be sufficient in tertiary flooding with low salinity water but with slightly slower recovery rate. Bentheimer sandstones known for its low clay content were subjected to polymer-augmented waterflooding at high and low salinity levels. Close secondary and tertiary recoveries were obtained for the two salinity levels with slower recovery rate for low salinity run. Minute clay content and water-wet characteristic as determined by contact angle measurements may explain the lack of water salinity effect on recovery. The lack of salinity role and the two shock fronts with connate water bank in between known to exist during low salinity flooding may explain the slower recovery rate encountered. Comparison of both sandstones indicates that less ultimate recovery from Berea rocks, and this can be attributed to their initial intermediate wet state in contrast to the water-wet Bentheimer sandstone rocks.

Evaluation of effecting factors on oil recovery using the desirability function

“…The contact angle pronouncing dominantly on the oil recovery agrees with the previous mention of Fig. 2b and was also concluded in the referred experimental work (Almansour et al 2017) as the main recovery mechanism, so-called the wettability alteration.…”

“…Three published works of coreflooding tests were examined which showed a practical application. The first correlation according to the experiment of Almansour et al (2017) implies that the oil recovery is affected by IFT, contact angle and oil viscosity after the data has been analysed using the combined desirability. By separating one of the three factors, the contact angle was found to dominantly govern the oil recovery which agrees with in the authors' conclusion.…”

“…A small number of data sets could result in a poor correlation, subsequently leading to the wrong conclusion. The previous cases of Almansour et al (2017) and Jeirani et al (2013) works are the good examples. The former has a relatively low number of data sets (4 data) having a low R 2 correlation while the latter has a relatively high number of data sets (160 data) leading to achieve an obvious fitting with high R 2 .…”

“…The result could be extended to predict a trend of the factors-and-indicator relation potentially if a good correlation is achieved. The selected published works are examined the proposed model consisting of three coreflooding tests: Almansour et al (2017) studied the polymer-low salinity injection in sandstone cores; Jeirani et al (2013) reported 160 flooding data of sandpack as a function of the oil-water IFT; Zhou et al (2000) conducted the systematic waterflooding in sandstones varying wettability, initial water saturation and permeability. Almansour et al (2017) conducted the fluid injection in sandstone cores (Berea and Bentheimer) whereas the polymer-augmented low salinity was introduced to use as a potential candidate fluid to enhance oil recovery.…”

Sensitivity Analysis and Optimization of the Effective parameters on ASP Flooding Compared to Polymer Flooding Using CMG-STARS

“…Extra, polymer flooding avoids the fingering phenomena and allows the displacing fluid to sweep total porous media when reaches production well [6]. More than, the benefits of polymer flooding include: Increase vertical and areal sweep efficiency, control the water/oil mobility, improved oil recovery, significantly less water required compared with typical water flooding and steam injection, and need low cost compared to the other expensive EOR method [7]. In oil wet reservoir rock, large amount of oil remained in porous media after primary and secondary oil recovery stages [8].…”