Microemulsion composition to increase injectivity of water produced in reservoirs

A method comprising:

• obtaining produced water from a production well in a reservoir;
• injecting a microemulsion into the reservoir via an injection well, the microemulsion comprising:
• a surfactant and a co-surfactant comprised in a range of values between 1% and 70% by volume, in relation to a total volume of microemulsion wherein the surfactant comprises a lauryl alcohol ethoxylate (LAE) or a sodium lauryl ether sulfate (SLES) and the co-surfactant comprises a low molecular weight alcohol selected from the group consisting of n-butanol, sec-butanol, iso-propanol, and isoamyl;
• an oil phase comprised in a range of values between 1% and 50% by volume, in relation to the total volume of the microemulsion;
• and
• an aqueous phase comprising a remainder of the total volume of the microemulsion;
• increasing a permeability of rock within the reservoir to the produced water in response to injecting the microemulsion;
• and
• reinjecting the produced water from the production well into the reservoir via the injection well simultaneously with the injection of the microemulsion such that the microemulsion is present at a concentration of 100-350 ppm based on a total volume of the injected microemulsion and the reinjected produced water.