In OIL, produced water is normally disposed into Alluvium sand reservoirs at shallow depths. While the disposal depths were in the ranges of 500 – 800 m till recent times, current statutory regulations require disposal to be carried out at depths below 1,200 m to ensure minimal risk of upward migration of such disposed water. In most of these disposal wells, injectivity had been found to be comparatively lower and rapid decline in injectivity is observed even after acid / solvent stimulation.

The presence of SRB was confirmed through API RP 38 standard procedure. SRB related corrosion was also observed in formation water handling and processing infrastructure. Solids generated due to high SRB activity along with high oil content and other suspended solids present was the primary cause of rapid decline in injectivity in these deep disposal wells. The entire problem was taken up for detailed study and identification of remedial measures jointly with a reputed microbial laboratory, M/s The Energy and Resources Institute (TERI), New Delhi, India.

Laboratory investigations included identification, characterization and isolation of various strains of SRB using 16S rDNA gene sequencing and designing different media compositions for inoculation and culturing of SRB strains. Microbial diversity of hyper thermophilic SRB in various produced water samples collected from different points were studied in details.

Through this study, suitable bactericides were identified and Minimum Inhibitory Concentration (MIC) optimized using Time Kill Test (TKT) method. The identified biocides were successfully field tested. The entire produced water from the said field is now being safely managed and disposed underground with sustained injectivity of disposal wells. The present paper discusses the results of laboratory findings and detailed field implementation data, for SRB control in the produced water disposal system.

You can access this article if you purchase or spend a download.