New Energy Efficient Method for Cleaning Oilfield Brines with Carbon Dioxide

Abstract

Water contaminated with hydrocarbons often results during the production of oil. The polluted water, which may be naturally occurring or a result of water or steam flooding operations, must be cleaned before disposal or re-injection. These brines are usually contaminated with emulsified oil droplets, 2 - 10 microns in diameter. Conventional phase separation techniques are often inadequate in cleaning such waters. Presently, gas floatation combined with chemical additives to promote oil droplet flocculation are used to purify these waters. However, if stricter discharge limits are imposed by the Environmental Protection Agency, the gas flotation method is likely to be inadequate. A new process was developed which utilizes carbon dioxide to clean oilfield brines. The new treatment method, described in this work, is actually an enhancement of existing gas flotation technology. The enhancement results from the use of carbon dioxide as the sweeping gas combined with its ability to lower the pH of the aqueous system. The reduction of pH neutralizes the charge on the surface of the drop, thus de-stabilizing the emulsion and enhancing phase separation. The water is simply neutralized by flashing the treated water to ambient pressure. The important discoveries of this study and an economic comparison of the carbon dioxide treatment process with other potential processes are presented in this paper.