The Issue: Bacteria in Oil and Gas Wells
The Solution: Treatment with Sabre's DiKlor® service, using chlorine dioxide (ClO2) stimulation process
A Texas based oil and gas company operates a gas processing facility in Southeastern New Mexico. 700 barrels (bbls) of wastewater per day are produced at the facility and pumped to a disposal well in the San Andres formation.
Chlorine Dioxide Application Considerations
The disposal well continually plugged and periodic acidizing was used in an attempt to restore the injection rate to at least a 700 BPD rate. Numerous acid treatments over a two-year period did not restore the well to the necessary 700 BPD level, or maintain improvement for an extended period of time. After acidizing, the injection rate would be down to a 300 BPD level within two months.
The operator installed a 15,000 bbl storage tank to hold the excess wastewater when the injection rate fell below 700 BPD. In addition, a 52-cartridge filter system was installed in an attempt to upgrade the disposal water quality. Despite these system modifications, plugging continued to be a serious problem. The storage tank eventually filled up, requiring the removal of excess water by truck at an annual cost over $50,000. Filter maintenance proved to be equally costly at approximately $30,000 per year.
Chlorine Dioxide Treatment Approach
A complete study of the wastewater stream and the disposal well was initiated, which resulted in the recommended use of Sabre’s DiKlor®service using chlorine dioxide. DiKlor® is staged with acid containing micellar solvent, corrosion inhibitor and iron chelant.
The DiKlor® service enhances conventional acid stimulation by oxidizing preferentially oil-wet sulfide to form water-wet hydrous ferric oxide which is then chelated by additives in the acid, and insoluble sulfide to water soluble sulfate. Chlorine dioxide also has the ability to oxidize biomass and polymer damage.
A treatment of 100 bbls of DiKlor® staged with an acid containing micellar solvent, corrosion inhibitor and iron chelant was required to stimulate the well, which cost significantly less than the operator’s current program.
Immediately after the DiKlor® service, injection rates exceeded 1,500 BPD. The storage tank was emptied and the injection pump was able to inject the 700 bbls in just 12 hours.
The job was a complete success and the excellent injection rates continued for 3.5 years, saving the operator approximately $80,000 annually. Recently, a plant turn-around caused considerable debris to be sent to the well and it plugged. The operator authorized a second stimulation using 150 bbls of DiKlor-S which returned the well to an injection rate in excess of 1,500 BWPD, where it has remained.
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, unlike conventional biocides. As it is a well-established EPA-registered biocide for use in drinking water and food, regulatory considerations are limited to local permitting requirements.
Over their 10-plus year use history in the petroleum industry, Sabre chlorine dioxide systems have a perfect safety record. This is due to their 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 on 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 during a catastrophic event. Sabre has a unique understanding of the health and safety issues related to the use of chlorine dioxide due to its extensive experience with the application of chlorine dioxide in both gas and solution phase.