Oilfield Produced Water for Re-use
Table1: Specifications for the Pilot-scale Reverse Osmosis/Nanofiltration Unit
Parameter Membrane size
Total surface area Material
Operating temperature Operating pressure Operating flow rate
Reverse Osmosis 9.75 x 100cm
spiral-wound cross-flow 7.6m2
Polyamide 40ºC 15bar
2.5m3/hour
Nanofiltration 9.75 x 100cm
spiral-wound cross-flow 7.6m2
Polyamide 40ºC 10bar
2.5m3/hour
concept, the reverse osmosis and nanofiltration processes were initially evaluated in a pilot-scale system. This system was installed at the Fazenda Belém field and adapted at the effluent treatment station, using the sand filter water stream outlet as feed water.
Aims The aims of this work were to use a pilot-scale system:
• To determine the efficacy of the reverse osmosis and nanofiltration technologies focusing on produced water re-use; and
• To assess the quality of the treated water in terms of physicochemical characteristics that can influence the re-use of this water for irrigation or other beneficial uses.
Materials and Methods Experimental Set-up
The experimental set-up of the pilot-scale system used during the field experiments is shown in Figure 3 and the characteristics of the reverse osmosis/nanofiltration modules are summarised in Table 1. The feed water stream was taken after the sand filter, from the full-scale treatment plant (see Figure 1). A cartridge filter (1.0µm) was used to set the feed water standard density index values below three, as recommended for reverse osmosis and nanofiltration membranes.
After the cartridge filter, the produced water was continuously fed to a high-pressure multistage centrifugal pump in order to provide the necessary flow (3.5m3/hour) and pressure (up to 15bar) for efficient membrane operation. It is important to note that the primary objective of this preliminary study was not to optimise the efficiency of the membrane system, nor to evaluate membrane fouling. The objective was to evaluate the decrease in salt concentration and other organic pollutants in the produced water intended for beneficial purposes.
Results and Discussion
The results for produced water characteristics prior to and after treatment with reverse osmosis and nanofiltration membranes operated with pH levels of 7.0 and 9.5 are presented in Table 2.
It is important to note, considering the analysis shown in Table 2, that the quality of the produced water before membrane treatment was already very good, indicating its high potential for re-use for beneficial purposes.
Both reverse osmosis and nanofiltration treatment systems transformed the raw produced water from oil wells that was unsuitable for discharge into very good quality water, suitable for
EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 2 95
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