Abstract: The enhanced oil recovery using seawater and EDTA (ethylenediaminetetraacetic acid) is a method that uses injection of EDTA in seawater to enhance the recovery of oil from sandstone reservoirs. The EDTA may be introduced into seawater during the initial extraction of oil from the reservoir by seawater injection, or a solution of EDTA in seawater may be used to flush residual oil from the reservoir after the initial extraction by seawater injection. In either case, the EDTA is present in about 1.0 wt % to about 5.0 wt % of the seawater solution, and the solution has a pH of between 10.5 and 11.0.

Abstract: The method of maintaining oil reservoir pressure involves injecting seawater having a concentration of about 1 wt % of a polyamino carboxylic acid or salt thereof as a chelating agent into the water zone of an oil reservoir, which reduces the formation of scale, thereby maintaining oil reservoir pressure. The polyamino carboxylic acid may be ethylenediaminetetraacetic acid (EDTA), acid (HEDTA), or hydroxyethyliminodiacetic acid (HEIDA). When used in larger concentrations, e.g., between 5 to 10 wt %, flooding the core with seawater containing the polyamino carboxylic acids not only prevents scale formation, but also improves core permeability. Instead of seawater, low salinity water may be used for the latter purpose.