Preliminary Study on Nitrate Injection to Control Souring Problem in Oil Reservoir: Benefits and Side Effects on Steel Material (UNS S31603)

The use of NBN in MEOR has two benefits: improved oil production and the prevention of reservoir souring. To date, little is known of the effects of NBN on SS type UNS S31603; one of the most widely used CRAs in petroleum industry. Therefore, an anaerobic experiment was performed by immersing SS samples for four weeks in batch culture systems containing brine water and 10% of crude oil, with and without NBN at 50°C. Open Circuit Potential (OCP) of the SS was monitored throughout the test; Cyclic Polarization Scan (CP) and surface analysis were performed at the end of experiment. The result revealed that the SS with NBN reached ennoblement after 10 days and remained stable until the end of the experiment. However, the SS without NBN demonstrated an unstable OCP throughout the experiment. The CP result showed that NBN protected SS from localized corrosion. Surface profile analysis using infinite microscopy showed more pits occurred on SS without NBN. Total bacterial count using a counting chamber showed that both free-living and bacterial biofilm in the system with NBN was slightly higher than the system without NBN. This study reveals that NBN used in MEOR could protect SS from localized corrosion.