Dynamic Water Flooding in Carbonates: The Role of Iodide Ions

Abstract

Seawater injection has demonstrated a successful and a well-established procedure for reservoir pressure maintaining and sweeping oil out of the reservoir. However, in most cases seawater by itself showed low incremental oil recovery, many research studies have shown that further dilution of the injected seawater is capable of altering the carbonate formation's wettability from mixed or oil-wet to more water-wet and therefore additional oil recovery. However, dilution requires massive volume of fresh water which is an expensive commodity and therefore it will not be practical in real applications. The following study provides for the first time a novel concept for boosting oil recovery with use of halides ions in very small concentrations without the need for seawater dilution. Halides ions (iodide ions) are added to the seawater with different concentrations (1000 ppm and 2000 ppm) to formulate what we call the "Dynamic Water". The efficiencies of the different prepared Dynamic Waters (with different iodide ions concentrations) were compared to seawater by performing IFT, contact angle, spontaneous imbibition and coreflooding experiments. Although all prepared Dynamic Water mixtures have higher salinity than seawater, they had insignificant impact on lowering the IFT, but they significantly alter the rock wettability to stronger water wet, which is an important oil recovery mechanism. The performance of the Dynamic Water on oil recovery was also investigated in this study by means of spontaneous imbibition and coreflooding experiments. Six samples were utilized for these experiments, three dolostones and three limestones. Initially, the three limestone samples were considered for spontaneous imbibition where Dynamic Water proved to be efficient in recovering oil from all the samples. After sample cleaning, the same three limestone samples in addition to the three dolostone samples were used for coreflooding under reservoir conditions of high pressure and high temperature. Good oil recoveries were achieved from almost all the samples by coreflooding, with maximum additional oil recovery of 16.9% from one of the limestone samples.

Influence of Halide Anions Cl–, Br–, and I– on the Zeta Potential of Oil-Wet Carbonate Surfaces

“…An injection fluid (dynamic water) based on the results of this study should allow to alter carbonate reservoir surfaces to be more water-wet and thus ultimately enhance oil recovery. This is very well in line with the previous results obtained in our group, investigating the impact of halide ions as an additive for seawater-based injection fluids by means of spontaneous imbibition and core flooding experiments …”

“…The increase of the magnitude of the negative zeta potential for modified calcite rock particles is therefore the result of the adsorption of polar oil components from the model oils and these components were not released when modified rock surfaces were conditioned in deionized water. It is therefore fair to say that deionized water alone has no strong effect to alter the surface wettability to more water-wet. , We have shown previously that halide solutions on the other hand are capable of turning rock surfaces to be more water-wet, which is likely due to the removal of adsorbed surface-active species.…”

“…Al Hamad et al found that interaction of 5k ppm NaI with carbonate rock could alter the wettability of carbonate rock and reduced the contact angle of an oil droplet from 40° in deionized water to 12° in 5k ppm NaI . They also reported an additional oil recovery of 4.5 and 15.8% during the spontaneous imbibition test for two different carbonate samples, when the samples were placed in 5k ppm NaI solution.…”

New Insights into the Application of a Magnetic Field to Enhance Oil Recovery from Oil-Wet Carbonate Reservoirs

“…The most common techniques used for EOR are gas injection, chemical flooding and thermal methods 2,3 . Several researchers have reported low recovery factors from carbonate reservoirs during water flooding due to the low spontaneous imbibition of water into the low permeability matrix 4 . The low imbibition of water into carbonate rocks is mainly attributed to the fact that most carbonate reservoirs are oil-wet oil 5 .…”

“…Nearly two-thirds of the world’s daily oil production is accomplished by using the technique of enhanced oil recovery from oil wells which have already passed their peak production capacities . The most common techniques used for enhanced oil recovery (EOR) are gas injection, chemical flooding, and thermal methods. , Several researchers have reported low recovery factors (RF) from carbonate reservoirs during water flooding because of the low spontaneous imbibition (SI) of water into the low permeability matrix . The low imbibition of water into carbonate rocks is mainly attributed to the fact that most carbonate reservoirs are oil-wet .…”