USE OF MULTIPLE TREATMENT AGENTS TO REDUCE HARDNESS OF AN OILFIELD PRODUCED WATER

摘要

A process is provided for treating a water to reduce its hardness byperforming a series of sequential stages including a primary chemical reactionstage, a secondary chemical reaction stage and a scale removal stage. Theprimary chemical reaction stage includes the steps of adding a first hydroxide iondonor in the form of lime to an initial water having an initial hardness andreacting the first hydroxide ion donor to form a first portion of a scale and anintermediate water having an intermediate hardness substantially less than theinitial hardness. The secondary chemical reaction stage includes the steps ofadding a second hydroxide ion donor in the form of caustic to the intermediatewater and reacting the second hydroxide ion donor to form a second portion ofthe scale and a product water having a product hardness substantially less thanthe intermediate hardness. The reduction contribution of the primary chemicalreaction stage to total hardness reduction is substantially greater than thereduction contribution of the secondary chemical reaction stage. The scaleremoval stage includes the steps of separating the scale from the product waterto form a sludge and disposing the sludge.