Mitigating Bacteria and H₂S at a Delaware Basin SWD Facility

Issue

A Delaware Basin saltwater disposal (SWD) facility faced severe bacterial contamination and hydrogen sulfide (H₂S) issues from varying produced water sources. High sulfate-reducing bacteria (SRB) levels (~10⁵ CFU/mL) caused H₂S gas (>100 ppm in tank vapors), toxic odors, and microbiologically induced corrosion (MIC). This led to pipeline pitting, daily filter clogging, declining well injectivity, and safety risks, threatening operations and regulatory compliance.

Recommended Solution

Chemical Injection Partners (CIP) proposed:

• Targeted Biocide Treatment: Continuous low-dose biocide injection (glutaraldehyde/quaternary ammonium) to kill SRB and prevent H₂S, with periodic shock doses.
• H₂S Scavenging: Temporary scavenger injection to mitigate H₂S gas for immediate safety.
• Operational Optimization: Inject biocide upstream of settling tanks, simplify chemical slate, and monitor H₂S, bacteria, and corrosion.
• Monitoring Plan: Routine sampling for H₂S, SRB, and corrosion rates to track progress.

Work Performed

CIP implemented a phased approach:

1. Initial Clean-Up: A chlorine dioxide (ClO₂) shock treatment (500 ppm) eliminated H₂S, oxidized biofilms, and reduced SRB, clearing tanks and pipelines.
2. Continuous Treatment: Installed metering pumps for 50 ppm biocide injection at the tank inlet, with weekly 100–150 ppm shock doses to prevent biofilm regrowth.
3. Monitoring and Adjustments: Twice-weekly tests (H₂S, bacteria, corrosion coupons) and weekly reports ensured efficacy. H₂S scavenger was tapered off as levels dropped, and corrosion inhibitor doses were optimized.

Results

Operational

• H₂S Eliminated: H₂S in water reduced from 15 ppm to <1 ppm; tank vapor H₂S dropped from 200 ppm to 0 ppm, ensuring safety and compliance.
• Bacteria Controlled: SRB counts fell from 100,000 CFU/mL to non-detectable, halting MIC.
• Improved Injectivity: Injection capacity increased 33% (12,000 to 16,000 barrels/day) at lower pressure, restoring well performance.
• Reduced Maintenance: Filter changes extended from daily to every 6 days; unplanned downtime dropped from 8 hours/month to zero.
• Asset Protection: Corrosion rates decreased from 12 mpy to 3–4 mpy, extending equipment life.

Financial

• Chemical Savings: Monthly chemical costs cut by 30% ($15,000 to $10,000), saving ~$60,000/year.
• Increased Revenue: Additional 4,000 barrels/day capacity could generate ~$1 million/year at $1/barrel.
• Avoided Costs: Prevented $100,000+ well workover and potential corrosion-related repair costs.
• Asset Longevity: Extended infrastructure life, deferring multi-million-dollar replacements.

Summary

CIP’s data-driven biocide program and continuous monitoring resolved bacterial and H₂S issues, enhancing safety, reliability, and profitability. The operator expanded CIP’s solution to other SWD facilities, demonstrating the value of tailored chemical management in midstream operations.