Technical Committee Production Engineering
Feasibility study for water treatment in the tail-end phase of gas production
In the present feasibility study technologies of treating oilfield or gasfield produced water are discussed with respect to their complexity and economic efficiency. The aim of water treating is the discharge of a high volume portion of water to a water stream and the grouting of a low volume portion to the bore hole. For this purpose developed and field-tested membrane- and adsorption- processes are described as well as further technologies for waste water processing. The electro-flotation which does not increase the charge of dissolved salts is evaluated as economic for separation of hydrocarbons, mercury, dissolved heavy metals and solids (3 to 15 €/m³). For removing high contents of BTX the stripping process (0,5 to 4 €/m³) is preferred over adsorption. Salts are separated by reverse osmosis (ca. 20 €/m³) in case of low concentrations and by evaporation (40 to 80 €/m³) in case of high concentrations.If, however, the total throughput does not exceed ca. 5 m³/h the water processing should be restricted to evaporation only. The purified water may be treated biologically (15 to 25 €/m³). The recovery of water is nearly 100% for surface waters, 96% for produced waters with low salt concentrations and 65% for produced waters with high concentrations.