EOR Back Produced Water Treatment: Media Selection to Improve Filtration Efficiency

Polymer flooding is one of the most advanced enhanced oil recovery techniques to improve production. It is a cost-effective method due to the properties of polymers, mainly its capacity to develop suitable viscosities when diluted, leading to an improved hydrocarbon's extraction. The technique consists in injecting Hydrolyzed Polyacrylamide polymer (HPAM), mixed with water, in the reservoir to reach a target viscosity, in order to guarantee oil extraction, while reducing a bit the water cut. However, back produced water viscosity is quite high and leads to poor water treatment efficiency. Several water treatment technologies for oil removal have been developed for this purpose using gravity separation, gas floatation, chemical treatment and filtration. The media filtration is one of the most attractive technology because it has low operating costs and can handle high flux rates; it can help switch from water flooding to polymer flooding by retrofitting existing water treatment facilities, and so minimize CAPEX. This technology is very efficient to treat the produced water (PW) and can reach a very low oil concentration (<5mg/L). Nevertheless the filtration efficiency is function of the PW quality as well as media selected for the filtration.

The aim of this study was to compare the efficiency of several media for the treatment of produced water and back produced viscosified water. The impact of the polymer concentration (500 mg/L) on the retention efficiency was demonstrated in batch and continuous modes on synthetic produced water (50 mgOil/L, 10 mg/L of calibrated particles, 100 mg/L corrosion inhibitor). Indeed, the high viscosity of the PW mostly increases the fouling velocities. First tests aimed at screening the oil retention in batch mode for 6 different kinds of media (3 nutshell, sand, and a polymeric media). The 3 best media were then tested in continuous mode (flow 15–25 m/h) with automatic cleaning phases. This phase allowed assessing the regeneration efficiency and the ageing of the media. Results of the tests concluded on the impact of the water quality on the retention efficiency and design parameter for the media filtration of back produced viscosified water. Thanks to this study, several selection criteria of media were highlighted to adapt this technology for each field case.