**3.4 Treatment technology of chemical flooding produced fluid in offshore platform**

Partially hydrolyzed polyacrylamides with high molecular weight (HPAM), after undergoing a series of chemical, mechanical, and thermal degradations, are back produced, making the oil-water interface highly electronegative and forming a strong electrical double layer. The repulsive force between oil droplets affects their aggregation and coalescence, and at the same time, the adsorbed polymers also increase the strength and viscoelasticity of the oil-water interface film. As a result, the emulsified oil droplets are of small particle size and strong stability. Therefore, the oil-water separation of produced fluid from polymer flooding is more difficult than that from water flooding. Hence, devices with much longer residence time and several times larger size are required for produced water treatment [17, 18].

However, platform space is limited for offshore oil fields; the abovementioned practice cannot be implemented. At present, the treatment process of polymer-containing produced fluid in Bohai oil fields is a so-called three-stage treatment process similar to that of water flooding. For example, the comprehensive water content of the produced fluid is 78% in Bohai A oil fields, and the average polymer concentration is 150 mg/L. The oil treatment system includes a one-stage three-phase separator, a two-stage thermal settling separator, and a conventional electric dehydrator (**Figure 5**). The wastewater treatment system mainly includes a tilted plate separator, a gas flotation unit (GFU), a walnut shell filter, and a residue conversion system. The abovementioned process represents the traditional process of produced fluid treatment for water flooding oil fields. For different polymer flooding oilfields, the original water flooding process have different complexity and methods for adaptive modification for polymer flooding projects.

**Figure 5.** *Treatment process of produced fluid in Bohai A oil field.*

*Development and Application of Chemical EOR Technologies in China Offshore Oil Fields DOI: http://dx.doi.org/10.5772/intechopen.88942*
