Oil Field Case Study: Control Bacteria in Oil and Gas Wells
The Issue: Bacteria in Oil and Gas Wells
The Solution: Treatment with Sabre's DiKlorSM service, using chlorine dioxide (ClO2) stimulation process
A Texas-based oil and gas company operated nine producing and five saltwater disposal wells in eastern Utah. Over time, the field became progressively sour as a result of contaminated water used in completion and workover fluids.
Chlorine Dioxide Application Considerations
The company’s producing wells generated 160 ppm H2S in the gas phase and +/- 5 ppm of soluble sulfide in the water phase, with active sulfate reducing bacteria growth throughout the field. The producer had a history of bacteria, (103 counts), and related problems, including H2S levels in the range of 80-90 ppm in the produced gas. The wells had been treated with various conventional biocides. These conventional biocides were unable to eradicate the sulfide problem that had built up in the wells and, therefore, it was necessary to find an alternative solution.
Chlorine Dioxide Treatment Approach
A complete study of the producer resulted in the recommended use of Sabre’s DiKlorSM service, using chlorine dioxide. DiKlor® was staged with acid containing micellar solvent, corrosion inhibitor and iron chelant.
In conventional acid stimulation the acid solubilizes carbonate and iron sulfide which remains in solution as long as the pH remains below 2. Once the acid is spent and the formation fluid pH rises above 2, the iron sulfide re-precipitates, plugging the pore spaces.
The DiKlorSM service enhances conventional acid stimulation by oxidizing preferentially oil-wet sulfide to form water-wet hydrous ferric oxide which is then chleated by additives in the acid, and insoluble sulfide to water soluble sulfate. DiKlor® also has the ability to oxidize biomass and polymer damage.
100 bbls of DiKlor® staged with 7.5% HCl acid was pumped through the coiled tubing to displace the volume of fluid in the hole with DiKlor®. The coiled tubing, along with a wash tool were then moved across the perforations to increase the coverage of the treatment. The well was shut in for one day after treatment before being brought back in production.
The Science of Success
Unlike alternative technologies, chlorine dioxide is a true gas that is a relatively stable oxidant, reacting only with reduced compounds such as sulfides, phenols, and biomass. Additionally, chlorine dioxide kills both active and inactive bacteria, unlike conventional biocides. Chlorine dioxide has also been shown to kill bacterial spores with relatively low contact times, and bacteria cannot build resistance to chlorine dioxide. It is also a well-established EPA-registered biocide for use in the drinking water and food industries.
Sabre has over a decade of experience in the petroleum industry, with a perfect safety record to match. This is due to inherent functionality, where chemical precursors are vacuum fed to the point of reaction to form chlorine dioxide in the absence of dilution. This formation of chlorine dioxide independent of the water stream allows Sabre systems to operate with any fluid, including oil, water, emulsions, and slurries. This unique chlorine dioxide system has been patented by Sabre.
Chemical precursors on portable Sabre chlorine dioxide systems are separated by secondary steel containment to further protect from accidental mixing. Sabre has a unique understanding of the health and safety issues related to the use of chlorine dioxide due to its extensive experience with chlorine dioxide in both gas and solution phases.