Tratamiento de aguas de la desalación del petróleo para su aprovechamiento en inyección al subsuelo

In the process of crude oil desalinization, wastewater is produced (congenital waters). These waters can be used in the injection wells to the subsoil. In order to achieve this procedure, wastewater treatment is required. The objective of this study was to define and to develop the best treatment system for the congenital waters, so that an effluent with the required quality can be obtained for its utilization in the injection wells. The characterization of the congenital water indicated a high content of chlorides and of sodium, as well as an extremely high hardness (4,500‐ 4,800 mg/L). Furthermore, the water contains bicarbonates, sulfides, and hydrocarbons (COD of 2,500‐2,900 mg/L). The treatability study was conducted in two stages: train tests in laboratory and physical simulation in pilot plant. In laboratory the feasibility of different processes and of its combinations was studied: precipitation‐coagulation and sedimentation, chemical oxidation, filtration, adsorption, aeration, decarbonation, and ionic exchange. The best doses of the chemical reagents were determined, and selected on the basis of the effectiveness of the processes. The best materials for filtration and adsorption were identified, the parameters for the removal of bicarbonates, the capacities of the resins of anionic and cationic exchange. According to the results and the respective analysis, four trains of treatment were proposed. The evaluation and the comparative analysis of the trains indicated that the best treatment of the congenital waters for utilization in subsoil injection, turned out to be water softening (lime-sodium carbonate), followed by oxidation with peroxide, decarbonation and filtration.