Dynamic Water Flooding in Carbonates: The Role of Iodide Ions

摘要

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.